NeoScan Manual: 3-Channel System

From Emagtech Wiki
Jump to: navigation, search

Contents

Overview

General Overview

NeoScan® real-time field measurement and scanning system is a turnkey, electric or magnetic field probe and measurement system. It can be configured as a near-field scanning system for mapping aperture-level field distributions with minimal invasiveness to the device or system under test. Or it can be used as a real-time field probe system for sensing or detecting electric and magnetic fields in a variety of media.

The NeoScan system can be used as an essential tool for test and evaluation of antennas and phased array systems and is particularly useful for phase characterization and calibration. Unlike conventional near-field scanning systems that utilize metallic radiators to pick up the fields, NeoScan probes are non-metallic, operating based on electro-optic (EO) or magneto-optic (MO) effects. Its field probes feature extremely small EO or MO crystals mounted at the tip of an optical fiber. The combination of the small probe size and absolutely non-metallic parts leads to the ultimate radio frequency (RF) non-invasiveness.

NeoScan provides detailed field maps of passive and active devices and circuits including RFIC’s and MMIC’s. Such invaluable information can effectively be used for design validation, model verification, diagnostics and fault isolation or performance evaluation of various parts of RF systems. It is also an alternative compact range for measurement of far-field radiation patterns of antennas and arrays, dispensing with a costly anechoic chamber. The system can be used in real-time, polarimetric and coherent sensing and probing of wideband signals and pulses, EMC/EMI testing, and medical device measurements and characterization of biological environments. The NeoScan system can be configured in a multi-channel architecture for simultaneous field measurement at multiple points and locations. Different channels can measure different polarizations in a coherent manner.

Features of the NeoScan System

  • Wideband operational bandwidth: few MHz to 20GHz, measuring repetitive signals with 50-ps rise time, 10-ns duration, and 80 V/m amplitude with a 10% to 90% definition
  • Hardware system sensitivity requirements of 2 V/m/√Hz
  • Electric field real-time measurement capability
    • Multi-port Integrated FC/APC Input
    • Multi-port SMA RF Output
  • Scanning measurement capability
    • Simultaneous measurement of amplitude and phase
    • Scanning area up to 80” x 80” (2 x 2 m)
    • 0.1 micron resolution linear encoder
  • Integrated Optical Bench:
    • 1550 nm Diode Laser (laser beam spot < 100 μm sq)
    • Polarization Controller and Analyzer
    • AC and DC photodetectors
  • Very wide dynamic range (>70 dB) and linear response range in 1 V/m to 2 MV/m
  • One normal field probe and two tangential field probe, each having a FC/APC optical fiber connector (Includes 10 m PM fibers on all probes)
  • System Operation, Monitoring, and Optimization Software

General Description

The NeoScan real-time field measurement & scanning system provides an entirely new capability for the measurement of high-intensity electric fields. This technology is based on the Pockel’s effect which measures the phase-retardance of an optical beam due to an impinging electric field. This electro-optic effect is observed in non-centrosymmetric crystals when an electric field is directed along certain crystal axes causes a change in the indices of refraction encountered by an incident optical beam. Figure 1.1 shows the basic principle of the electro-optic effect. The electro-optic effect provides a means of modulating the phase or intensity of the optical radiation. In another sense, this effect also makes it possible to detect the presence of an electric field impinging on the crystal. The polarization of an optical beam travelling through a crystal is altered by the electric field in that crystal. The comparison of polarization states allows determination of the amplitude and phase of the existing RF electric field. Since the electro-optic sensing phenomenon relies on small displacements of the atomic crystal structure, the response time of the process is extremely short. This short response time makes it possible to measure high-frequency electric fields up to the terahertz regime.

Figure 1.1: EO modulation of an optical signal.

A typical EO probe is composed of an optical fiber affixed with an EO crystal coated with a dielectric reflection layer on its bottom surface as shown in Figure 1.2. These probes have very delicate optical interconnects and extreme care must be taken in handling the probes to prevent excessive shock, bending and out of plane stresses.

Due to its broad measurement bandwidth and high spatial resolution, the EO measurement technique is a promising means to characterize RF systems such as microwave and millimeter-wave integrated circuits, HPM sources and systems, and large-scale active arrays and other radiating structures. Unlike the conventional electrical measurement techniques which require some type of metal structure for the resonant detection of an RF signal, NeoScan’s unique real-time EO electric field measurement method requires no metal components. As a result, the field perturbation caused by introducing metal within the vicinity of a device under test (DUT) is significantly reduced.

Figure 1.3 shows the electric and magnetic fields distribution of a traveling RF wave with a normal probe shown in typical orientation. To detect the maximum electric field in this configuration, the propagation direction of the optical beam of the probe should be parallel to the E-field direction. In general, a normal EO probe is only sensitive to the electric field component parallel to the probe handle, whereas a tangential probe is sensitive to the electric field component perpendicular to the probe handle. Yet, the E-field sensitivity of a tangential probe depends on its crystal orientation sitting on its tip.

Figure 1.2: A single-axis EO probe. The probe tip is protected by Epoxy to provide nearly identical performance to a bare probe.
Figure 1.3: Illustrates a normal field measurement as oriented with respect to an incident electric field. The normal probe is oriented with the probe normal to direction of propagation.

A low noise 1550 nm laser diode is used as optical beam source. The optical connections are fiber-based. The beam is delivered to an optical probe. The polarization of the beam is modulated through an electro-optic crystal on the probe tip. The modulated beam is reflected back into the fiber, and back to the mainframe for analysis. An optical analyzer converts the polarization change of the beam into an amplitude change. The amplitude is linearly proportional to the strength of the external electric field at the probe-crystal location. The equation E=αV is used to calculate the electric field, where α is the calibration factor, or the slope between the electric field E (in V/m) and the measured EO signal V (in V/m/uV). For instance, for a calibration factor of 1.082 V/m/uV. a measured EO signal of 1000 uV (0.001 V), corresponds to and electric field of 1.082 V/m/uV x 1000 V = 1082 V/m.

Figure 1.4: An example of a real time measurement of a 6.6 nsec pulse with 10 kV/m peak field strength. The upper trace shown on the oscilloscope is the input signal, and the lower trace is the measured signal.

Due to the fast response of the EO crystal, it is possible to measure extremely high-bandwidth signals with the normal SNR limitations of wideband signal detection. Using this capability, EMAG Technologies Inc. has developed the world’s first fiber-based real-time polarimetric electric field sensor system – NeoScan – for the measurement of high-power microwave signals. Figure 1.4 is an example of a real time measurement of a 6.6 nsec pulse with 10 kV/m peak field strength. The upper trace shown on the oscilloscope is the received signal, and the lower trace is the detected signal.

The NeoScan system is capable of measuring signals with bandwidths up to 20 GHz and signal levels as low as 1 V/m for optical probes with a 10 m PM fiber. Because the optical probes are free of metallic parts, it is possible to measure extremely high-field strengths since there are no free electron surfaces to generate arcing. The NeoScan can measure fields up at least 2 MV/m and possibly higher.

System Overview

The NeoScan real-time field measurement and scanning system consists of:

  • An optical mainframe with a touchscreen control computer that can be used for either real-time high power microwave measurement or E-field scanning as shown in Figure 1.5.
    Figure 1.5: The NeoScan Optical Mainframe System.
    Figure 1.6: NeoScan 2-axis translation stage.

    The power switch on the back will turn the system and the laser on or off. It is recommended to turn the NeoScan system on at least 30 minutes before any operation for warm-up. A USB port is used to communicate with control computer. The “Signal Out” channels can be used for real-time measurements. The RF signal can be displayed either on a high resolution oscilloscope or a spectrum analyzer. The channels can also be configured for near-field scanning measurement with a U-jumper SMA Cables. The scanning configuration can measure both amplitude and the phase of the signal with a Lock-in Amplifier.

  • One normal probe and two tangential probes
  • One 2-axis translation stage with a stage controller for scanning operation (Figure 1.6)
  • One RF Lock-In Amplifier
  • One GPIB-USB cable for instrument control
  • One USB multi-port Hub for instrument control
  • The NeoScan system control software package

Additional equipment needed to configure NeoScan as a field scanning system include:

  • A signal generator to provide the local oscillator (LO) signal for NeoScan’s output mixer
  • A signal generator to provide a 100 MHz reference signal to lock-in amplifier

The Front Panel of NeoScan Optical Mainframe

The front panel is the main interface to the system. It contains a control computer that that runs Microsoft Windows, and controls, commands, and monitors the NeoScan system’s status (Figure 1.7).

Figure 1.7: The Front panel of NeoScan Optical Mainframe.

The Rear Panel of NeoScan Optical Mainframe

The rear panel is the interface to the instruments and provides complete access for external control, optical fiber excitation, and RF signal output (Figure 1.8). It contains:

  • A USB interface port for computer control of the system
  • The power switch and red LED Power indicator for turning on or off the system
  • The AC power cord. The AC power requirement is 110V, 60Hz with a 250V 2A fuse
  • Three SMA connector for RF output (Signal Out)
  • Three fiber FC/APC connector (Probe)
  • SMA connectors for frequency scanning mixer includes: IF Out, LO In, and RF In
  • SMA connectors for IF Switch Out and IF Switch Ins
  • An electric fan

Figure 1.8: NeoScan Real Panel.

Acronyms and Abbreviations

2D: 2-dimentional
3D: 3-dimentional


A/D: Analog-to-Digital
AC: Alternating Current
AFCW: Air Filled Coax Waveguide


BSO: Bismuth Silicon Oxide


CAL.: Calibration
CH/Ch: Channel
cm: centimeter
CP: Circular polarization
CW: Continuous Wave (Pure Sine Wave)


D/A: Digital-to-Analog
DAQ: Data Acquisition
dB: Decibel
dBm: Decibel power referenced to milliwatts
DBR: Distributed Bragg reflector
DC: Direct Current
DUT: Device under test


EMC: Electromagnetic Compatibility
EMI: Electromagnetic Interference
EO: Electro-Optic


FC/APC: Ferrule Connector / Angle-polished connection, a fiber-optic connector
FEP: Fluorinated ethylene propylene, a copolymer of hexafluoropropylene and tetrafluoroethylene


GPIB: General Purpose Interface Bus
GRIN: Graded index lens


Hz: Hertz


IF: Intermediate Frequency/The low frequency signal port of a mixer.


LED: Light emitting diode
LNA: Low-Noise Amplifier LO: Local Oscillator/The carrier input port of a mixer
LTO: Lithium Tantalate (LiTaO3)


m: meter
mm: millimeter
msec: millisecond (ms)
mW: milliwatt
MMIC: Monolithic Microwave Integrated Circuits
MO: Magneto-Optic


nsec: nanosecond (ns)


PD: Photodetector
PM: Polarization maintaining
PM: Phase Modulation
Pol. Ctrl.: Polarization controller


Ref Level: Reference Level
RF: Radio Frequency/The high frequency signal port of a mixer
RFI: Radio Frequency Interference
RFIC: Radio Frequency Integrated Circuits
RT: Real-time


s: Second (sec)
SA: Spectrum Analyzer
SBIR: Small Business Innovative Research
SMA: Subminiature connector ‘A’, a coaxial RF connector
SNR: Signal-to-noise ratio (signal power over noise power)


TEM: Transverse Electromagnetic
TEM cell: A small chamber generating a consistent electromagnetic field for testing small RF devices


USB: Universal Serial Bus
um: Micrometer (m)
uV: Microvolt (V)


V/m: Volt/meter
V: Volt

Measurement Preparations

Signal Strength Check

You should have a reasonably large enough EO signal in order to perform a measurement or scan. In other words, the EO signal level must be much higher than the noise level (-90 dBm) as shown in Figure 3.1. Therefore, you have to do a quick check to see if your signal strength is strong.

Figure 3.1: A typical EO signal in Spectrum Analyzer.

Requirements during the Signal Strength Check

The following instruments are needed for a signal strength check:

  1. NeoScan optical mainframe

  2. Either one normal or one tangential probe

  3. One Coplanar Waveguide (CPW) board for generating electric field

  4. A RF Lock-in amplifier

  5. A signal generator

  6. A synthesizer for generating RF source to device under test

  7. A 2nd synthesizer for mixing Local Oscillator (LO) source

  8. Probe fixture

  9. One GPIB-USB cable for Lock-in amplifier (Figure 3.2)

    Figure 3.2: GPIB-USB cable.

  10. One BNC – SMA cable

  11. One USB multi-port Hub

  12. One USB cable for optical mainframe

  13. SMA RF cables

  14. BNC cables for 10 MHz reference

Signal Strength Check Setup and Procedure

It is assumed that NeoScan optical mainframe is already on. Figure 3.3 shows the set up for a signal strength check.

Figure 3.3: NeoScan Signal Strength Test and Optimization.
  1. Gently unwind the fiber and deploy the sensor head(s) at measurement location or on the probe fixture.

  2. Gently clean and attach the appropriate fiber connector to the correct fiber port of the NeoScan system (Probe 1, Probe 2, or Probe 3).

    • Do not excessively pull or bend the fiber.

    • Do not bend or strike the probe tip.

  3. Make sure all cables and fibers are in safe positions.

  4. Secure the probe on probe fixture. If you are using a 2-axis translation stage, gently insert the probe inside the hole located on probe holder and fasten the screws – see sections 2.3 and 2.8 for more details.

  5. Rotate the tangential probes around to align crystal E-field sensitivity direction to the field, see Figure 3.4.

    Figure 3.4: Positioning a probe above the slot of a Coplanar Waveguide (CPW).

  6. Connect the U-jumper RMA cable from “Signal Out” to “RF In” in Channel 1, 2 or 3 as shown in Figure 3.5.

    Figure 3.5: NeoScan Rear Pane set for Channel 1(top) and Channel 2 (bottom).

  7. Set up the Signal Generator for Lock-in amplifier. Plugging its power cord into an electrical receptacle. Set it as 100 MHz and 0 dBm. Connect the signal generator output to Lock-in amplifier reference input (“REF IN”) on its front panel.

  8. Set up Lock-in amplifier. Plugging its power cord into an electrical receptacle. Connect the GPIB-USB cable from the (back panel of) Lock-in amplifier to USB Hub (Figure 3.6).

    Figure 3.6: Rear panel of Stanford Research Systems SR844 RF Lock-In Amplifier.

  9. Connect the “IF Out” on mainframe front panel to the “Signal In” on Lock-in amplifier using a BNC – SMA cable.

  10. Set up a RF synthesized signal generator for generating RF source to the CPW. Plug its power cord into an electrical receptacle. Connect RF synthesized signal generator to CPW feed using a SMA cable. Set the operating frequency fo (GHz).

  11. Set a 2nd RF synthesized signal generator for mixing Local Oscillator (LO) source. Connect it to “LO In” on the front panel of optical mainframe with a SMA cable. Set the frequency to fo + 0.1 (GHz) and the power to +15 dBm (regardless of the frequency). The NeoScan system will receive RF signals from the Electro-optic probe. The signal is then amplified and ultimately mixed with the output of the second RF synthesized signal generator. The mixed signal is then fed into the Lock-in amplifier, where the amplitude and phase are measured. For example, if your RF source to the CPW is set at 1 GHz, the correct setting for the 2nd synthesized signal generator would be either 0.9 GHz or 1.1 GHz. This provides a 100 MHz signal out of the IF Out port on the NeoScan optical mainframe with an amplitude equal to at the Signal Out/RF In connection. This is the signal being fed into the Lock-in amplifier Signal In port.

  12. Connect the 10 MHz Reference OUT in the back panel of the signal generator (as the driving source for the 10 MHz synchronization network) to the 10 MHz Reference IN of the two RF synthesized signal generator using BNC cables. The Lock-in amplifier does not have a 10 MHz Reference input. The RF output of the 100 MHz signal generator (set to 0 dBm) is then connected to the Ref In on the Lock-in amplifier. This will synchronize the Lock-in amplifier to the synchronized synthesizers. Alternatively, you can select the 100 MHz signal generator to be the master and connect its 10 MHz Reference Out to the 10 MHz Reference In on the RF synthesized signal generator. Then connect the 10 MHz Reference out of the RF synthesized signal generator to the 10 MHz Reference In on the 2nd RF synthesized signal generator.

  13. Turn the signal generator on. Make sure its “Modulation Generator” key is off.

  14. Turn on Lock-in amplifier. The on/off power switch is located in the rear panel (Figure 3.6).

  15. Turn the RF synthesized signal generators on. Toggle the front panel RF ON/OFF key to turn on RF power to the “RF OUTPUT” port. The display “RF ON” annunciator will turn on.

  16. Bring the probe down close to the surface of CPW in such a way that the probe positions right above the CPW slot and move it around the slot to detect an EO signal.

    • To get the maximum EO signal, use a microscope (and a lamp for the microscope illumination) to adjust the probe height with the Z micrometer on the XY Linear Translation Stage.

  17. Open NeoScan Optical Bench Manager program.

NeoScan Optical Bench Manager Program

NeoScan Optical Bench Manager program monitors optimization status of the system. The optimization process finds the polarization status of the polarization controller, and saves the optimized parameters and corresponding optical powers into the files.

Icon OBM.png
Open NeoScan Optical Bench Manager program by double clicking on NeoScanOBM icon Icon OBM small.png on desktop or Windows Explorer. The user interface of the program consists of two pages: System Monitor page and Optimization Settings page (Figure 3.7). By default, the program opens up with “System Monitor” page.

Keep NeoScan Optical Bench Manager program running until the end of the experiment or measurement.

Figure 3.7: NeoScan Optical Bench Manager Program.

System Monitor Page

When the program starts, the system detects the total return power and the polarization power in the channel, plots their variations over time and displays their numerical values in mW. Figure 3.8 indicates that channel 1 is selected to deliver the beam to optical probe with Probe ID No. 1505. The Probe ID No. is a four-digit integer number provided by EMAG Technologies Inc. The green “Probe Detected” indicator indicates that the probe is connected to the correct channel.

Figure 3.8: The total return power and the polarization power of delivered beam to the optical probe with Probe ID No. 1505 in channel 1.
  1. Select the channel number you want to use for the measurement using the dropdown list labeled “Select Channel” (Figure 3.9). “Ch n” denotes channel n where n = 1, 2, ... NeoScan Optical Bench Manager program opens up with the “Ch 1” as the default working channel.

    Figure 3.9: Selecting the working channel from NeoScan Optical Bench Manager window.
  2. Enter “Probe ID No.” as the number marked on the fiber associated with the probe.

  3. Press “Set Probe ID” button to update (Figure 3.8).

    • When either the total return power or the polarization power is too low (less than 0.3 mW), the information panel will remind a user to correct the problem. This can be the case if the probe is not connected or is defective.

    • When the user presses “Set Values” button, the previous (existing) saved optimization parameters/voltages will be applied to the polarization controllers of the selected channel. The program will check whether the polarization state is maintained or not.

  4. To start a new probe optimization press “Apply” button.

If the polarization is maintained, the total return power and the polarization power will lie within the specified optimized range (the default value is ±20%). In this case, “Optimization Indicator LED” becomes green. Otherwise, it start blinking and the information panel indicates: “Polarization is not maintained: Optimization is required.” A user can change the threshold from the box labeled “Auto Trigger Margin” (see Figures 3.7 and 3.8). If the power difference is greater than 20%, the polarization state is found not to be maintained, therefore, the user will be prompted with a dialog window giving an opportunity to initiates the optimization process or skip the optimization by choosing “No.”  

The “Stop” button stops the application. To close (kill) the NeoScan window click on exit button Icon Exit.png on the top far right in the LabView user interface. To re-start running the program press the start button Icon Start.png located on the top left in the LabView window as shown in Figure 3.10. During the run, the start button will disappear. Keep NeoScan Optical Bench Manager program running until the end of the measurement.

Figure 3.10: Start and Stop buttons for NeoScan Optical Bench Manager.
  • The message box in “Information Panel” displays messages of warnings, actions and results.

  • “Save Plots” saves in folder C:\ProgramData\NeoScan\OpticalBenchHistory.

  • A user can reset the graphs by pressing “Reset Plots” button. The updated start time will be displayed under the power graph after “Started at” and in the information panel.

  • There are two options to display power plots: The “Entire History” option displays the power plots from the time Optical Bench Manager program started (numerically is displayed as Start Project Time in information panel). The “Updated” option displays the power plots after resetting the plots (pressing “Reset Plots” button), see Figure 3.11.

    Figure 3.10: Resetting the power plots and displaying them with the Entire History and Updated options.

Optimization Settings Page

To set the optimization parameters, press “Optimization Settings” tab in NeoScan Optical Bench Manager program (Figure 3.11): Make sure the GPIB-USB cable from the back panel of Lock-in amplifier is connected to the NeoScan USB Hub.

Figure 3.11: Optimization Settings page in NeoScan Optical Bench Manager program.
  1. Set Lock-in amplifier from “Lock-in Amplifier Settings” section (Figure 3.12). Put down the Visa menu and select the appropriate GPIB address for Lock-in amplifier Visa. The default is GPIB0::8::INST.

    Figure 3.12: Lock-in Amplifier Settings in Optimization Settings Page.
  2. If you change any value, press “Set Values” button to update.

  3. Set Lock-in amplifier parameters:

    1. Set Lock-in amplifier sensitivity. The sensitivity of Lock-in amplifier is the rms amplitude of an input sine (at the reference frequency) which results in a full scale DC output (10Vdc).

    2. Select “Time Constant” from the dropdown lists. The default for time constant of the output low-pass filter that determines the bandwidth of Lock-in amplifier in 10 ms.

  4. Press “Set Values” button to update.

  5. Other parameters that should be directly set on SR844 RF Lock-in amplifier – since they are not controlled:

    •  Time constant: 24 dB/oct, Figure 3.13(a).
    •  Signal Input: 50  Low noise, Figure 3.13(b).
    •  Sensitivity: Low noise, Figure 3.13(c).
    •  X display: R(dBm), Figure 3.13(d).
    •  Y display: θ, Figure 3.13(e).
    •  Remote: 50 Ω external source, Figure 3.13(f).
    Figure 3.13: Stanford Research Systems SR844 RF Lock-In Amplifier: (a) Time constant: 24 dB/oct, (b) Signal Input: 50 Ω Low noise, (c) Sensitivity: Low noise, (d) X display: R(dBm), e) Y display: θ, (f) Remote: 50 Ω external source.

    The signal levels at the Signal In port on the Lock-in amplifier are in the range of -100 dBm to -40 dBm or higher, depending on device one measures. It is important to set the sensitivity of the Lock-in amplifier greater than the expected input signal amplitude at the Signal Input port (from the IF Out of the optical mainframe). For example, if you expect a signal less than -67 dBm but greater than -87 dBm, set the sensitivity to -67 dBm and 100 μV (rms) setting. If the input signal is greater than the input signal setting, an OVERLOAD condition will occur and the red LED OVERLOAD indicators on the Lock-in amplifier will flash.

    • If the largest tolerable noise signal (at the input) exceeds the full scale signal, the red LED OVLD indicators in lock-in indicate that the readings may be invalid due to an overload condition. In this situation, you many try increasing the time constant or to use a larger full scale sensitivity.

  6. Keep the default values for other parameters. Table 3.1 lists the default values for the main parameters used in the optimization process, see Figure 3.14.

  7. Optimization parameters are stored in C:\ProgramData\NeoScan\OptimizationParameters folder.

Table 3.1: Default values for the main parameters used in the optimization process.
Parameter Description Default Value
Lock-in Amplifier Visa Lock-in Amplifier GPIB address GPIB0::8::INSTR
Sensitivity Lock-in Amplifier Sensitivity 100 uV / -67 dBm
Time Constant Lock-in Amplifier Time Constant 10 ms
No. Averaging Points Number of points used to find the peak value 5
Variation Limit Maximum variation from the nominal value 1.00 dBm
PC Voltage Maximum voltage applied to the polarization controllers during the optimization process. 3.0 V
Voltage Steps Voltage steps applied to the polarization controllers during the optimization process 0.01 V
Wait Time Interval delay time 1000 ms
Figure 3.14: Optimization parameters settings in Optimization Settings Page.

If the optical signal is low, check to make sure:

  • The probe and the crystal on its tip is fine.

  • The operating frequency is correct.

  • All the components are connected correctly and appropriately.

  • All instruments are functioning properly.

  • All cables and the PM fiber are fine.

  • All connectors are in good conditions – make sure they are not loose.

  • CPW is functioning properly.

  • Lower the probe down close to the surface of CPW and make sure the probe positions right above the CPW slot and move it around the slot.

Probe Optimization

The NeoScan software monitors and controls the polarization of the optical beam in the system. The optimization status for each probe at each channel needs be maintained for an extended period of time. Not only an initial optimization process for each probe at each channel is needed, but also additional optimization processes are needed if the status is not maintained. In general, you have to perform optimization whenever you detach the fiber connectors from the fiber ports of the NeoScan system or when the fluctuation in the total return optical power and the polarization power are varied more than 20%. After the optimization procedure, the system is ready for real-time measurement or scan.

Optimization Setup and Procedure

It is assumed that NeoScan optical mainframe is already on. The setup for the optimization procedure is similar to Signal Strength Check setup as described in section 3.1.2.

To get the maximum EO signal:

  1. Move the probe around the CPW slot using the X or Y Miniature Translation Stages.

  2. Position the probe right above the CPW slot.

  3. Using the Z Miniature Translation Stage and lower the probe down close to the surface of CPW as much as possible.

NeoScan Optimization Utility Program

Figure 3.15: Dialog window for initiating the optimization process.
In order to initiate an optimization, it is assumed:
  • The channel number and the Probe ID No. of the probe you want to optimize are selected.

  • The steps described in section 3.2.2 in “Optimization Settings Page” have been done (GPIB address of the Lock-in Amplifier, Time Constant, and the Sensitivity, have been already chosen).

  • Press “Apply” button to start new probe optimization (Figure 3.7).

A user is presented with a dialog window shown in Figure 3.15, giving an option to initiates the optimization process – which will take about 20 minutes to be completed – or skip the optimization by choosing “No.” Click on “Yes” for optimization. The system will remind a user to prepare an optimization structure. Align crystal field sensitivity direction to optimization structure field properly and press “Continue”.

When the optimization process starts, NeoScan Optimization Utility window will pop up, and the detailed optimization parameters are displayed to a user (Figure 3.16): Table 3.1 lists the main parameters used in optimization process with their default values. The change of the return power and the EO signal are plotted during the optimization process as shown in Figure 3.17, and their values are displayed in the boxes labeled “PD Power” and “EO Signal”, respectively. a user can monitor “Polarization Controller Parameters” through the information panel shown in Figure 3.18.

Figure 3.16: NeoScan Optimization Utility program.


Figure 3.17: Change of the return power and the electro-optic signal graphs during the optimization process (left to right direction indicates the start to the end of the process)

The optimization process takes about 20 minutes. It can be used to diagnose hardware failures. When the phase optimization has completed, the optimization window will prompt a user to perform a probe stability test through a red blinking “Start Stability Test” button at the bottom of the Window (Figure 3.19). To perform the probe fiber stability test, press the “Start Stability Test” button shown in Figure 3.19. An information dialog box will pop up and explains the procedure for the test. Press “Close” button in dialog box and then lift the middle of the fiber at least 2 m from either the probe head or the optical connector. Move it up and down, and/or left and right several times. The program will record variations in return power on the screen. Be sure not to pull the fiber at the connector or the probe ends. After performing this for approximately 30 seconds, press “End Stability Test” on the window. If signal fluctuations during the motion remains within the variation limit (default value is 1 dBm), the optimization is considered to be valid, otherwise, the program will repeat optimization (see Figure 3.20).

At the completion of the signal optimization process, the optimization window will disappear and the display will return to NeoScan Optical Bench Manager window. The optimized parameters will be written in files in ProgramData\NeoSca\OptimizationParameters.

You have to perform an optimization:

  1. When you attach the fiber connectors to the fiber ports of the NeoScan front panel,

  2. Whenever you detach a fiber connector from to the fiber ports of the NeoScan front panel and re-attach it to the same or the any other port.

  3. When the fluctuation in the total return optical power or the polarization power are varied more than the defined threshold value (default value is 20%).

  4. When there is an abrupt and sharp change in temperature.

  • If the Probe ID No. is not correct, NeoScan Optical Bench Manager cannot find the files for optimization parameters, therefore, a user will be prompted with a warning dialog window shown in Figure 3.21.

When the voltages to the polarization controllers for a channel are set to the correct optimized values, you “may” observe a sharp change in the polarization power as shown in Figure 3.22. You can save the power plots by pressing “Save Figures” button.

Figure 3.18: Information Panel in NeoScan Optimization Utility program.


Figure 3.19: Stability Test in NeoScan Optimization Utility.


Figure 3.20: Comparison of a completed optimization process with a failed one in NeoScan Optimization Utility program.


Figure 3.21: Warning dialog window when the files for optimization parameters are not found.


Figure 3.22: The change in the polarization power after applying the optimization voltages to the polarization controllers.

Near Field Mapping

Near Field Scanning

The scanning measurement maps the electric field distribution near a device under test (DUT). During each scan, both the magnitude and the phase of the particular electric field component are measured. The probe is attached to a probe fixture mounted on the computer controlled translation stage to allow the probe to be scanned in two directions.

Requirements for Scan

The following instruments are needed for scanning measurement:

  1. NeoScan Optical Mainframe

  2. Either one normal or one tangential probe

  3. A 2-axis translation stage

  4. A RF lock-in amplifier

  5. A signal generator

  6. A synthesizer for generating RF source to device under test

  7. A 2nd synthesizer for mixing Local Oscillator (LO) source

  8. Probe fixture for translation stage

  9. One GPIB-USB cable for lock-in amplifier

  10. One USB multi-port Hub

  11. One USB cable for optical mainframe

  12. One BNC – SMA cable

  13. SMA RF cables

  14. BNC cables for 10 MHz reference

Scan Setup and Procedure

The setup for the scanning procedure is similar to Signal Strength Check and Probe Optimization setup as described in section 3.1.2 except for replacing the CPW with a DUT (Figure 4.1). It is assumed that NeoScan Optical Bench Manager program is running and the probes has been optimized at channels as it was discussed in section 3.3:

Figure 4.1: NeoScan Scanning Measurement Setup.
  • Setup the 2-axis translation stage and gently insert the probe inside the probe holder and fasten the screws (see section 2.8).

  • Set up the DUT near the reach of translation stage (and the probe on the probe fixture).

  • Plug 2-axis translation stage power cord into an electrical receptacle. Connect the translation stages as daisy chain. See section A-I.1.3 for more details.

  • Connect a USB cable from the X-axis translation stage to the USB multi-port Hub. Turn on translation stage power.

  • The probe stays connected to the correct fiber “Probe” of the NeoScan system.

  • For a tangential probe, select the E-field sensitivity direction. The probe must be oriented along the X-axis to scan the X-component of the electric field. It should be re-aligned along the Y-axis to measure the Y-component. During each scan, both the magnitude and the phase of the particular electric field component are measured.

  • Make sure the DUT is placed on a flat and level surface. Use a level for a quick measurement. Alternatively, use the micrometer mounted on top of the translation table and measure the probe height from the surface of the DUT in its three corners – as shown in Figure 4.2.

  • Open NeoScan Mapping Utility program.

Figure 4.2: Measuring the flatness of the DUT.

NeoScan Mapping Utility Program

NeoScan Mapping Utility program is the central command center used in the 2D field scan application. The program creates the project folder, sets the appropriate parameters for lock-in amplifier, controls translation stage, including the speed setting and 2D movement settings, and scanning of an electric field. NeoScan Mapping Utility interface includes five pages:

  • Project Settings Page: Creates the project folder, sets the operating frequency and the calibration factor;

  • Hardware Settings Page: Sets the translation stage parameters including the location of the origin (scan starting point) and speed of the stage, as well as lock-in amplifier parameters;

  • Height Settings Page: Sets the Probe Height and estimates the optimal antenna scan parameters for far field pattern measurements;

  • Scan Settings Page: Sets scan parameters, including the number of scan points and the step size;

  • Scan Control Page: Scans a 2D field and display real-time near field maps.

Icon MAP.png
To open NeoScan Mapping Utility program double-clicking on NeoScanMAP icon Icon MAP small.png on desktop Windows Explorer. By default, NeoScan Mapping Manager program opens up with “Project Settings” page (Figure 4.3).

Make sure the GPIB-USB cable from the back panel of lock-in amplifier and the USB cable from the X-axis translation stage are connected to the NeoScan USB Hub.

Project Settings Page

The NeoScan system designates C:\Users\neoscan\Documents\NeoScan\Projects as the parent folder in which all data files from a scan will be saved as project folders in this directory.

  1. Create a project folder by entering the title in Project Name Entry Box and pressing “Create Folder” button.

  2. Select the operation frequency from the box labeled “Frequency.”

  3. Set the “Calibration Factor.”

    • “Project Description” editor enables a user to create and edit a text file.

    • The project name should have a maximum of 25 characters. Do not use “Empty Space” or any of the following characters: `  ! @ " # $  % ^ & * ( ) + = \ | / { } [ ] , > <  :  ;  ?. Note that it is allowed to use “dot” in project name, for example, you can choose patch_2.349GHz as your project name.

    • When you start NeoScan Mapping Utility program a folder called “Untitledproject” is created automatically in parent folder. Failed to press “Create Folder” button, all data files will be written in “C:\Users\neoscan\Documents\NeoScan\Projects\Untitledproject” folder (Figure 4.4). A user can rename the files appropriately after NeoScan Mapping Utility program is stopped.

Figure 4.3: NeoScan Mapping Utility program: Project Settings Page.


Figure 4.4: Project Box in NeoScan Mapping Utility program, after starting the program (left), and when entering a project name (right).

Hardware Settings Page

It is assumed that the users are familiar with the operation of the “Translation Stage.” Otherwise, it is highly recommended that you read Appendix A-I. Press “Hardware Settings” tab in NeoScan Mapping Utility interface (see Figure 4.5).

Figure 4.5: Hardware Settings page in NeoScan Mapping Utiltiy program.
  1. Set lock-in amplifier parameters:

    1. Select the Lock-in Amplifiers for each channel using the Lock-in Amplifier Selector and set their corresponding parameters.

    2. Put down the Visa menu and select the appropriate GPIB address for lock-in amplifier Visa The default is GPIB0::8::INST.

    3. Set lock-in amplifier sensitivity. The sensitivity of lock-in amplifier is the rms amplitude of an input sine (at the reference frequency) which results in a full scale DC output (10Vdc).

    4. Select “Time Constant” from the dropdown lists. The default for time constant of the output low-pass filter that determines the bandwidth of lock-in amplifier in 10 ms.

    5. Press “Update Settings” button to reload new values when you make changes. The system will respond with "Updated settings" message in information panel to confirm the settings if the values are appropriate. Otherwise, it asks you to check the parameters.

      Other parameters that should be directly set on SR844 RF lock-in amplifier – since they are not controlled (see Figure 3.13 in section 3.2.2):

    • Time constant: 24 dB/oct
    • Signal Input: 50 Ω Low noise
    • Sensitivity: Low noise
    • X display: R(dBm)
    • Y display: θ
    • Remote: 50 Ω external source

    The signal levels at the Signal In port on the Lock-in amplifier are in the range of -100 dBm to -40 dBm or higher, depending on device one measures. It is important to set the sensitivity of the Lock-in amplifier greater than the expected input signal amplitude at the Signal Input port (from the IF Out of the optical mainframe). For example, if you expect a signal less than -67 dBm but greater than -87 dBm, set the sensitivity to -67 dBm and 100 μV (rms) setting. If the input signal is greater than the input signal setting, an OVERLOAD condition will occur and the red LED OVERLOAD indicators on the Lock-in amplifier will flash.

    • Make sure the GPIB-USB cable from the (back panel of) each lock-in amplifier is connected to the USB Hub.

    • If the largest tolerable noise signal (at the input) exceeds the full scale signal, the red LED OVLD indicators in lock-in indicate that the readings may be invalid due to an overload condition. In this situation, you many try increasing the time constant or to use a larger full scale sensitivity.

  2. To set translation stage speed settings:
    1. From “Visa COM” serial port drop-down list select the COM port that the X Linear Translation Stage is connected to. A COM port is a specific serial connection on a computer, such as COM3.

    2. Set the speeds of translation stage from “Translation Speed” box (Figure 4.5). The default value is 10 mm/s – indicating that translation stage can move 10 mm per second.

    3. Press “Set Speed” button to save the new settings. The system will respond with confirmation message “Set Speed OK” in information panel. The Scan Speed is ~ 0.3 mm/s.

    4. When translation stages power up, they need to be homed in order to get an accurate reference position. The home sensor is at the motor end of the stage. Press “Home Position” button.

  3. In order to displace translation stage to a defined position along X-axis, enter the appropriate X coordinate in the X Position Setting Entry Box and then press “Move along X” button as shown in Figure 4.6. Similarly, enter the appropriate Y coordinate in the Y Position Setting Entry Box and then press “Move along Y” button to move to the defined position (see Appendix A-I for more details).
  4. Use “Set Origin” button to define the starting point of the scanning area (Figure. 4.6). See Appendix A-I for more details.

  5. To go to the origin, press “Move to Origin” button.

Figure 4.6: HSetting X and Y position of translation stage (left), and setting the origin (right) in NeoScan Mapping Utility program.

Height Settings Page

Set the probe height – the distance between the probe and the DUT surface – using the knob (Figure 4.7). If you are interested in high resolution scanning, you may skip the other parameters, which will be discussed later in the chapter on Far Field Measurements.

Figure 4.7: NeoScan Mapping Utility program: Probe Height Settings Page.

Scan Settings Page

In order to scan the distribution of electric field on a DUT, three parameters are needed to be known:

  • Dimensions of the probed (scanned) area in X and Y directions (DPX, DPY);

  • The step size ∆X and ∆Y that represents the spacing between points along X-axis and Y-axis, respectively;

  • Probe height or the distance of the probe to the DUT surface.

To be more precise, one needs Nx x Ny points to scan the whole area, where N_x=DXP/∆X and N_Y=DYP/∆Y. For instance, 4624 points (68 x 68) are needed in order to scan a 34 mm x 34 mm Patch Antenna with resolution of 0.5 mm (500 μm). The effects of the Step Size (scan resolution) and Probe Height on the 2D Amplitude near field maps for 2.349 GHz Patch Antenna are shown in Figure 4.8.

Figure 4.8: The effects of the Step Size (scan resolution) and Probe Height on the 2D Amplitude near field maps for 2.349 GHz Patch Antenna.

To set scan parameters, press “Scan Settings” tab in NeoScan Mapping Utility program (Figure 4.9).

Figure 4.9: NeoScan Mapping Utility program: Scan Settings Tab.
  1. Switch ON mode enable the user to scan the three channels simultaneously using a single Lock-in Amplifier.

  2. Select the channel(s) you want to scan by checking the check boxes (Figure 4.10).

    Figure 4.10: Setting Scan Parameters in Scan Settings Tab.

  3. Use the Data Label text boxes to choose a name of the files the data to be written. By default the program automatically reads the current working channel. “Information” editor enables a user to add a text on the data file header.

    • The Data Label should have a maximum of 25 characters. Do not use “Empty Space” or any of the following characters: `  ! @ " # $  % ^ & * ( ) + = \ | / { } [ ] , > <  :  ;  ?. Note that it is allowed to use “dot” in project name.

  4. Enter the number of points you want to scan in X and Y direction in entry boxes labeled “No. Point X” and “No. Point Y,” respectively (Figure 4.10).

  5. Set the step size in each direction in entry boxes labeled “Step Size X” and “Step Size Y,” respectively. These values are in mm.

  6. Select “What Axis to Scan First?” By default the program start scanning Y-axis first. In either case the scan data is written in a file in the same format, see Figure 4.11.

    Figure 4.11: Setting directions of scan using “What Axis to Scan First?” .

    • The information panel will display the total number of points that has to be scanned (Nx x Ny) in the box labeled “Total No. of Points”.

    • The program will also calculate the “Single Move Time” for each scan point (without delay) and displays the “Estimated Scan Time”.

    • The user can control the dwell time from “Dwell Control” key (Figure 4.12). The Dwell Time is the amount of time spent recording the signal for one data point for a channel before moving to the next point. By default, “Dwell Control” key is set to “Auto”. This introduces few msec dwell time during the scan. To change the dwell time, select the “Manual” option from “Dwell Control” button and enter the desired value in box labeled “Manual Move Time” in “Manual Move Setting” section (Figure 4.12). You can view the new “Estimated Scan Time” by pressing the “Update Scan Time” button.

    Figure 4.12: Manual Move Settings in Scan Settings Tab.

Scan Control Page

It is assumed that the scan parameters are set and the scan measurement setup has been setup. In order to start the scan, press “Scan Control” tab in NeoScan Mapping Utility program (Figure 4.13).

Figure 4.13: Scan Control Tap in NeoScan Mapping Utility Program.
  1. Press “Start Scan” button to start the scan.

  2. The program displays 2D Amplitude and 2D phase contour plots of the measured amplitude and phase during the scan, as shown in Figure 4.14. Graphs are rescaled continuously during the scan. This enables the users to monitor the status of the scan. For instance, any sudden change or any instrumental failure can appears as anomalous pattern in either 2D plots.

  3. The “Pause Scan” and “Stop Scan” buttons control the scan process. During scanning, use “Pause Scan” to pause temporarily the scanning. Pressing the “Stop Scan” button during scanning, will stop the scanning process.

  4. The “Plot Display?” key allows a user to display 2D Amplitude graph in dBm or μV unit. Similarly, “Current Signal” and “Current phase” in information panel present the lock-in amplifier current readings during the scan (Figure 4.15).

    Figure 4.14: 2D Amplitude (in dBm unit) and 2D phase contour plots of the measured amplitude and phase during the scan.


    Figure 4.15: 2D Amplitude (in μV unit) and 2D phase contour plots of the measured amplitude and phase during the scan.
    • A user can check the “Elapsed Scan Time” and view the current X and Y position of the probe from the information panel (see Figure 4.16).

    • During the scan, there is no access to other tabs or pages in NeoScan Mapping Utility program.

    • When a signal falls below -150 dBm, a warning message appear in Information Panel indicates that “Detected a signal < -150 dBm in Ch 1 -- much below the noise level.” You may check the data later.

The “Stop” button stops the application. To close (kill) the NeoScan window click on exit button Icon Exit.png on the top far right in the LabView user interface. To re-start running the program press the start button Icon Start.png located on the top left in the LabView window, see Figures 4.5 and 4.16.

Figure 4.16: A completed scan of a Patch Antenna by NeoScan system.

The NeoScan Scan Data

During each scan, both the magnitude and the phase of a particular electric field component at a plane are measured. When the scan is completed, data are written in .DAT files in your defined (created) project folder, say “patch_2.349GHz,” in the parent folder, i.e. C:\Users\neoscan\Documents\NeoScan\Projects\patch_2.349GHz.

For each scan the amplitude of the measured field, the phase of the field, and the scan information are written in the files – defined by Data Label – in project folder. All amplitudes are given in units of V/m and all phases in degree. The scan file also contains the basic information about the scan including the operating frequency (in GHz), correction factor, the number of points for scan and the step sizes (in mm) and etc. Figure 4.17 shows the contents of data file “E_X_Dir.DAT”, in “patch_2.349GHz” folder representing scan of 2.349 GHz patch antenna along the X direction:

During a scan, data is collected and immediately displayed by NeoScan Mapping Utility program. However, data will be written into the files at the end of the scan.

Figure 4.17: Contents of data file E_X_Dir.DAT in patch_2.349GHz folder

NeoScan Visualization Utility

During each scan, both the magnitude and the phase of a particular electric field component at a plane are measured. Measured data can easily be interpreted and understood when displayed as 2D or 3D graphs. Visualization of the NeoScan scan data are realized by LabVIEW based programs. It plots the amplitude and the phase of the measured field distribution on a horizontal plane after the scan. NeoScan Visualization Utility includes three pages: Settings, Near Field Maps, and Far Field Patterns.

Icon Plot.png
Open the NeoScan Visualization Utility program from Desktop or Windows Explorer by double clicking on the NeoScanVisual icon Icon Plot small.png. By default, NeoScan Visualization Utility program opens up with “Settings” page (Figure 5.1).
Figure 5.1: NeoScan Visualizarion Utility Program.

Settings Page

By default NeoScan Visualization Utility program consider the “Project Folder”:

C:\Users\neoscan\Documents\NeoScan\Projects

as the parent folder in which all saved data are stored.

In order to view the plots of scan data:

  1. Press “Open File 1” button as shown in Figure 5.1. This opens up the dialog window, where direct you to the project in parent folder where you want to open a data file, see Figure 5.2.

    Figure 5.2: Selecting a data file (E_X_Dir.DAT) from project folder (patch2.349GHZ) from the dialog window.

  2. Choose the desired data file – e.g., E_X_Dir.DAT in project folder patch2.349GHz – and then press “OK” button in the dialog window.

    • “Information Panel” and “Project Description” will display all scan information regarding the selected project and scan (Figure 5.3).

      Figure 5.3: Project Description Panel and Information Panel in NeoScan Visualization Utility program.

  3. Similarly, the user can open file 2, and 3 to display simultaneously.

  4. Press “Near Field Maps” tab from NeoScan Visualization Utility program to view the plots.

Near Field Maps Page

NeoScan Near Field Maps page displays either 2D or 3D plots of the amplitude and phase distribution of the scanned field from saved files. It includes 2D Plot page and 3D Plot page.  

2D Plots Page

When you enter “2D Plot” page, 2D contour plots for amplitude and phase distributions of the scanned field are plotted and the maximum and minimum of their values are displayed in the boxes next to the graphs (Figure 5.4).

Figure 5.4: 2D plots in NeoScan Near Field Maps Page.
  • By default, the program plots fields in V/m units. You can use the key labeled “Amplitude Unit?” to display them in dBV/m (Figures 5.4 and 5.5).

    Figure 5.5: 2D Amplitude graphs in units of dBV/m (left) and V/m (right).

  • The “Phase Shift” knob adds an angular shift (in degree) to the phase distribution (Figure 5.6).

    Figure 5.6: Effect of 90° phase shift on 2D Phase graph.

  • The Phase Threshold knob will sets any phase below a minimum field threshold (in V/m) to zero. Figure 5.7 compares the 2D Phase graph without a phase threshold (left) with the one with a phase threshold when the minimum field is set to 10 V/m (right).

    Figure 5.7: 2D Phase graphs without (left) and with a phase threshold, setting the minimum field to 10 V/m (right).

  • By default, NeoScan Visualization Utility program fits the 2D graphs into the square window. If the DUT is other than a circle or regular polygon such as square, equilateral triangle, etc. you must choose the “Maintain Ratio” option in “View Fit?” in order to keep the object proportional. As an illustration, Figure 5.8 presents the comparison of 2D amplitude plots for field distribution of a 12 mm × 220 mm (rectangular) slotted waveguide antenna with different view options when “View Fit?” key is set to “Fit to Window” (left plot) and when “Maintain Ratio” option is chosen (right plot).

    Figure 5.8: Comparison of 2D amplitude plots for field distribution of a slotted rectangular waveguide antenna with different view options; When “View Fit?” key is set to “Fit to Window” (left plot) and when “Maintain Ratio” option is chosen (right plot).

  • Press “Save Graphs” button to save all plots. The plots associated with a project are saved in a folder called “Plots” within the same folder.

  • You can zoom in and out the graphs by clicking on the zoom button (Figure 5.4).

3D Plots Page

To view 3D plots, press the “3D Plots” tab in Near Field Maps page (Figure 5.9).

  • 3D Amplitude graphs can be plotted either in dBV/m or V/m using the key labeled “Amplitude Unit?”

  • The “Phase Shift” knob adds an angular shift (in degree) to the phase distribution.

  • Users can choose the plot style using “Plot Style” dropdown window (Figure 5.10). It includes:

    • cwLine
    • cwPoint
    • cwLinePoint
    • cwHiddenLine
    • cwSurface
    • cwSurfaceLine
    • cwSurfaceNormal
    • cwContourLine
    • cwSurfaceContour

    The default format is “cwSurface.”

  • To adjust the graph degree of transparency use “Transparency” knob or Transparency Entry Box as shown in Figure 5.11.

Figure 5.9: 3D plots in NeoScan Plot Utility Page (with cwSurface plot style).


Figure 5.10: 3D plots in Fig. 5.9 with cwPoint plot style.


Figure 5.11: Effect of transparency level on 3D plots: 0% transparency level (left) and 50% transparency level (right).

The “Stop” button stops the application. To close (kill) the NeoScan window click on exit button Icon Exit.png on the top far right in the LabView user interface. To re-start running the program press the start button Icon Start.png located on the top left in the LabView window, see Figure 5.1.

Far Field Patterns Page

The far field pattern measurement and utility are discussed in details in section 6.

Far Field Patterns

Far Field Patterns

Figure 6.1: The probed area is a function of the DUT physical dimensions in X directions (DXa) and the angular range.
Far field patterns are calculated from measured near field data. The accuracy in the evaluation of far field pattern from near field measurements is a function of the spatial resolution of the probing grid (∆X, ∆Y), the probe height (h), and the probed area (DXP, DYP). As shown in Figure 6.1, the probed area is a function of the DUT physical dimensions in X and Y directions (DXa, DYa) and the angular range over which the far field pattern calculation would be very accurate in X and Y directions.(θmaxX, θmaxY):

DXP = DXa+2 h tan⁡θmaxX,

DYP = DYa+2 h tan⁡θmaxY,

As the distance between the probe and the DUT surface increases, field components show broadened distribution and some details observed at shorter distance are no longer recognizable in the near field maps. However, near fields from a DUT at different probe heights (say 1 mm and 4 mm) generate relatively similar far field patterns.

Estimating the Optimal Antenna Scan Parameters

The “Height Settings” page in NeoScan Mapping Utility program estimates the optimal antenna scan parameters for far field pattern measurements. For instance, in order to calculate the far field patterns of a 34 mm x 34 mm 2.349 GHz patch antenna from a high resolution measured near field data, it is required that the probe height to be set at 1 mm with scan step size of 0.5 mm (500 μm). To achieve this you have to scan a total of 4624 points (68 x 68). However, the optimal antenna calculation suggests that you can achieve similar results for far field pattern by setting the probe 4 mm above the patch antenna and setting the step size at 1.995 mm. That is, you have to only scan 32 x 32 = 1024 points. This will deteriorate the near field resolution, yet it cuts the scanning time by half.

To measure the far field patterns you have to follow the procedure explained in section 4.2. However, before setting the scan parameters (discussed in section 4.2.4) in order to estimate the optimal values for the far field measurements parameters:

  1. Icon MAP.png
    Press “Height Settings” tab in NeoScan Mapping Utility page (Figure 6.2).
    Figure 6.2: Aperture Settings tab in NeoScan Mapping Utility program.

  2. Enter the DUT physical dimensions (in mm) in “Physical Aperture Size X” and “Physical Aperture Size Y” boxes (Figure. 6.3).

    Figure 6.3: The scan starting and end points of a patch antenna.

  3. Choose the angular range (θmaxX, θmaxY) in degrees, over which the far field pattern calculation would be very accurate, in boxes named “Max Theta X” and ” Max Theta Y”.

  4. Enter the “Probe Height.”

    • By default, the “Probe Height” will be automatically set to λ/3. You can change this value by entering the new value in the box. “Wavelength” in information panel calculates the wavelength (λ) corresponding to the operating frequency.
  5. Press “Calculate” button.

  6. The program calculates the optimal scan area size, i.e., the starting point and the end point in a scan. For instance, the program suggests that the “Scan Area Size X” and “Scan Area Size Y” for a 34 mm × 34 mm 2.349 GHz patch antenna with a probe 1 mm about the antenna is 41.5 mm (Figures 6.3 and 6.4). That is, the scan starting point should be ½ (41.5 - 34) = 3.75 mm away from a corner of the antenna. “No. Points X” and “No. Points Y” in information panel present the suggested values for number of scanning points in X and Y directions and those of step sizes (in mm) will be displayed in “Step Size X” and “Step Size Y,” respectively.

  7. Press “Scan Settings” button to export automatically the suggested values to the scan settings in “Scan Settings” page. Otherwise, the initial values in “Scan Settings” page are kept unchanged.

    • The program returns the limits for the Fresnel and Fraunhofer Zones and give a notice whenever the probe height falls outside these zones (Figure 6.4). The Fresnel Zone is defined as 0.62√(𝐷3/𝜆), and the Fraunhofer Zones is expressed as 2𝐷2/𝜆 where D is DUT physical dimensions and 𝜆 denotes the operating frequency wavelength.
    Figure 6.4: Information Panel for Aperture Settings Page.

Far Field Scans

NeoScan Visualization Utility program uses the near field maps of an antenna measured by the NeoScan system to estimate its radiation patterns using a near-to-far-field transformation based on the EM.Cube's FDTD simulation engine for far field calculations at the completion of an FDTD time marching loop. The main difference is that the FDTD Module uses a closed surface, known as the Huygens box, which completely encircles the radiating structure. In this case, however, NeoScan uses a 2D horizontal plane placed slightly above the surface of the antenna aperture. This plane, supposedly, must extend to infinity in the lateral directions. NeoScan Visualization Utility plots far field radiation pattern in both Cartesian and polar coordinate systems.

There are 13 parameters for far field calculation:

Table 3.1: Default values for the main parameters used in the optimization process.
Frequency Operating frequency (in GHz)
No. Points X Number of points for scan in X-direction
No. Points Y Number of points for scan in Y-direction
Step Size X Spacing between points along X-axis (in mm)
Step Size Y Spacing between points along Y-axis (in mm)
Column Direction ±X
Row Direction ±Y
Normal Direction +Z (Normal Direction of the DUT)
Ex_AMP Ex Amplitude
Ex_PHA Ex Phase
Ey_AMP Ey Amplitude
Ey_PHA Ey Phase
Resolution Resolution of calculation for θ and ϕ
Icon Plot.png
All amplitudes and phases from scan are required for the tangential X and Y components of the electric field. In order to view the far field patterns open the NeoScan Visualization Utility program:
  1. Press “Open File 1” button.

  2. Choose the desired data file that will be used as Ex data file in Far Field Calculation and then press “OK” button in the dialog window (Figure 6.5).

    Figure 6.5: Selecting Ex and Ey data files for Far Field Patterns Calculation.

  3. Press “Open File 2” button.

  4. Choose the desired data file that will be used as Ey data file in Far Field Calculation and then press “OK” button.

  5. Press “Far Field Patterns” tab in NeoScan Visualization Utility program (Figure 6.6).

    Figure 6.6: Far Field Patterns page in NeoScan Visualization Utility program.

  6. Set the resolution of calculation for θ and ϕ (in degree) from the box labeled “θ, ϕ Resolution.” The default value is 3°. Figure 6.7 presents the comparison of the far field radiation patterns for a 10.65GHz slotted waveguide with 1° and 5° resolutions.

    • For this version of the software, Column corresponds to scan along +X (left to right), and Row corresponds to scan along +Y. Normal Direction of a DUT is considered to be along +Z. </li
    Figure 6.7: A comparison of the far field radiation patterns for a 10.65GHz slotted waveguide with 1° and 5° resolutions.
  7. Press “Calculation” button to call the far field executable engine to run.

    • A black RUN window appears while the engine is running. It disappears as soon as the calculation is completed.
  8. The output files for project “patch_2.349GHz” comprises the Cartesian Radiation Patterns in the XY, YZ, and ZX plane

    • patch_2.349GHz_FF_PATTERN_Cart_XY.DAT
    • patch_2.349GHz _FF_PATTERN_Cart_YZ.DAT
    • patch_2.349GHz _FF_PATTERN_Cart_ZX.DAT

    and the polar Radiation Patterns in the XY, YZ, and ZX plane

    • patch_2.349GHz _FF_PATTERN_Polar_XY.ANG
    • patch_2.349GHz _FF_PATTERN_Polar_YZ.ANG
    • patch_2.349GHz _FF_PATTERN_Polar_ZX.ANG

    They are written in C:\Users\neoscan\Documents\NeoScan\Projects\ patch_2.349GHz folder.

  9. The radiation pattern is plotted in both Cartesian and polar coordinate systems (Figure 6.8). Use the “Coordinate” buttons to change the plane cut of the far field patterns to XY, YZ, or ZX.

    Figure 6.8: Cartesian and Polar plots of ETotal in dB for a path antenna.

  10. Switch a log scale graph to the linear one from the “Amplitude Unit” key.

  11. A user has options to plot the total field (ETotal) or the θ and ϕ components (Eθ, Eϕ) of the field using the button labeled “View Plots?” (Figure 6.9).

    Figure 6.9: Cartesian and Polar plots of Eθ and Eϕ for a path antenna in linear scale.

  12. To compare plots use “Scale Plots?” button.

  13. Use ‘Save Graphs’ Button to save all 12 pictures. The plots are saved in “Plots” folder in corresponding project folder.

  14. EM.Grid is a Data Visualization and Calculation tool based on EM.Cube simulation environment, which provides the user with much more options for plotting the far field radiation as shown in Figure 6.10.

    Figure 6.10: EM.Grid Data Visualization and Calculation Tools in NeoScan Visualization Utility program.

The “Stop” button stops the application. To close (kill) the NeoScan window click on exit button Icon Exit.png on the top far right in the LabView user interface. To re-start running the program press the start button Icon Start.png located on the top left in the LabView window, see Figure 5.1.

Capturing Fields in Real Time

Real-Time Field Measurement

In a real-time field measurement, NeoScan detects a real-time signal and display it on a high-speed digital sampling oscilloscope. Real-time measurement is used to accurately characterize broadband pulses and other waveforms. The actual pulse measurement, however, falls far below the thermal noise of the electro-optic system, and so a large number of coherent averages are required to recover it. This is accomplished by collecting successive samples on a high speed digital oscilloscope triggered by a highly stable arbitrary waveform generator which is also generating the pulse. The digital oscilloscope collects a large number of samples.

Requirements for Real-Time Measurement

The following instruments are needed for real-time measurement:

  1. NeoScan Optical Mainframe

  2. Either a normal or a tangential probe

  3. A digital oscilloscope with averaging function and a sampling speed ≥ 4 GS/s

  4. A pulse generator (RF synthesized signal generator)

  5. High pass filter

  6. SMA cables

  7. BNC cables for 10 MHz reference

Real-Time Measurement Setup and Procedure

It is assumed that NeoScan Optical Bench Manager program is running and the probes has been optimized at channel 1. NeoScan Real-Time measurement setup is shown in Figure 7.1:

Figure 7.1: NeoScan Real-Time Measurement Setup.
  1. The probe stays connected to the correct fiber “Probe” of the NeoScan system.

  2. Connect oscilloscope’s channel 2 to the channel of NeoScan system (“Signal Out”) with a male-to-male SMA cable.

  3. Set up a RF synthesized signal generator for generating RF source to a DUT. Connect RF synthesized signal generator to DUT feed using a SMA cable.

  4. Connect RF synthesized signal generator Pulse Sync Out to oscilloscope’s channel 1 via a high pass filter (such as inline filter SHP-500+). The Pulse Sync Out on the RF synthesized front panel provides the trigger in into channel 1 of the scope.

  5. Synchronize the 10 MHz reference for RF synthesized signal generator and oscilloscope on their rear panels. Connect the 10 MHz OUT in the back panel of the RF synthesized signal generators to the 10 MHz IN of oscilloscope using a BNC cable.

  6. Plug in the oscilloscope and RF synthesizer power cords into an electrical receptacle and turn them on.

  7. Turn the RF synthesized signal generator on. Toggle the front panel RF ON/OFF key to turn on RF power to the “RF OUTPUT” port. The display “RF ON” annunciator will turn on.

  8. Set the RF synthesized signal generators for pulse mode with 2 μsec period and a 120 ns pulse width.

  9. Set the scope to average the output of the NeoScan channel using the math avg function – e.g. Scope resolution of 16K with maximum avg of 1000000. This eliminates the random noise.

The key here is to trigger the Pulse Sync Out of the generator. Thus, the waveform generator creates a pulse synchronously with a marker signal. The marker signal triggers the oscilloscope, and it begins sampling after a specified delay (see Figure 7.2).

Figure 7.2: Real-time field measurement using a high-speed digital oscilloscope.

Due to the fast response of the EO crystal it is possible to measure extremely high-bandwidth signals with the normal SNR limitations of wideband signal detection. Based on this capability, NeoScan can be used as a real-time polarimetric electric field sensor system. It can be used for the measurement of wideband signals with an instantaneous bandwidth up to 20GHz. Figure 7.3 shows an example of a real time measurement of a 6.6 nsec pulse with 10 kV/m peak field strength. The upper trace shown on the oscilloscope is the received signal, and the lower trace is the detected signal.

Figure 7.3: An example of a real time measurement of a 6.6 nsec pulse with 10 kV/m peak field strength. The upper trace shown on the oscilloscope is the input signal, and the lower trace is the measured signal.

Appendix I: Working with Translation Stage

NeoScan Translation Stage

NeoScan translation stage is an essential part of the scanning system that allows the probe to be scanned in two directions along X or Y axis. It is composed of a two Zaber motorized Linear Translation Stages that can be controlled using the control computer and USB communications through NeoScan Mapping Utility program.

XY Linear Translation Stage

The XY Linear Translation Stage is composed of a two computer controlled motorized Linear Translation Stages that are connected in the daisy-chain via serial port (Figure A-I.1). There are two axes of motion: X and Y. The X Linear Translation Stage is mounted on the Y Linear Translation Stage. While a carriage on the X stage moves along X direction – using the rotary motors – the X stage can move along Y direction. The cables provide convenient connection of motors and encoder signals. Units with rotary motors also include a shaft-mounted knobs (Knob X and Knob Y), for manual control in the X and Y direction. The Z Linear Translation Stage (micrometer Z) on the translation stage is anticipated for precise adjustment of the probe height. A plastic probe fixtures as a supporting arm has been mounted on moving stage by a single screw, holding the probe. The probe sits inside the probe holder located on head of the probe fixture and is secured by four plastic screws.

Figure A-I.1: XY Linear Translation Stage Components.

Installing XY Linear Translation Stage

Unpack the NeoScan translation stage components. To install:

  1. Place the Y Linear Translation Stage on a stable flat table, preferably an optical table. You shohld fasten it to the table by screws.

  2. Mount the X Linear Translation Stage on the Y Linear Translation Stage using four screws as shown by red screws in Figure A-I.2. When the Y stage carriage is located at the start point, use the holes in the middle of the X-axis stage to attach it to the Y-axis stage carriage. The screws pass through the clearance holes in the stage base and thread into the carriage of the lower stage (Figure A-I.3). If using longer screws than the ones included, make sure that they do not go too far through the lower carriage and interfere with the stage mechanics. It may be necessary to move the carriage to gain access to the holes in the stage base.

    Figure A-I.2: Installing NeoScan Translation Stage.


    Figure A-I.3: Mounting the X Linear Translation Stage on the Y Linear Translation Stage using four screws.

  3. Mount the Plate on the X Linear Translation Stage. Fasten its four edges with screws as indicated by green arrows in Figure A-I.2.

  4. Place X, Y, and Z Miniature Translation Stages (Micrometer) on the front edge of the Optical Plate and fasten its four edges with screws as indicated by arrows in Figure A-I.4.

    Figure A-I.4: Installing the X, Y, and Z Miniature Translation Stages (Micrometer).

  5. Attach the Plastic Probe Fixture to the Z Miniature Translation Stage.

For alignment:

  1. First, loosely attach lower axis stage to breadboard using mounting bolts (Figure A-1.5).

    Figure A-I.5: Alignment. Loosely mounting the Y-axis on a flat surface (a). Aligning Y-axis (b). Aligning X-axis (c). Loosely mounting and aligning Z-axis (d).

  2. Then, use a machinist's square to align the lower axis stage with an edge of the breadboard and tighten the mounting screws.

  3. Next, loosely attach the next axis and align the bases of these two stages using the machinist's square as shown. When the stages are aligned, tighten the mounting screws.

  4. If a Z-axis is to be used, install it loosely as shown in Figure A-1.4. Use the machinist's square as a straight edge to align the Z-axis stage with the carriage of the stage it is attached to. It may help to have a small amount of tension on the mounting screws, so the z-axis stage can be moved, but with a little resistance. When it is aligned, tighten the screws.

A few precautions:

  • The translation stages may produce enough force to cause personal injury. Be careful to keep hair, body parts, jewelry, and clothing from being caught in moving components. Pinch labels are used on our devices to indicate areas of particular concern.

  • During continuous operation, a device’s motor may feel hot to the touch. Although this is normal, care should be taken when handling the device. If the device emits a burnt smell, it may be damaged, in which case, you should cease operation, and contact Customer Support for assistance.

  • To reduce the risk of electrostatic damage, avoid touching the electrical contacts of the data cables included with your device(s).

  • Do not expose device(s) to vibration or shock.

  • Do not expose device(s) to extreme conditions, such as temperatures exceeding device ratings, radiation, and dusty or humid environments.

  • Do not submerse device(s) in liquid.

Translation Stage Setup

  1. Set up the translation stage on a stable flat table, preferably an optical table.

  2. Set up the DUT near the reach of the translation stage.

  3. Make sure that nothing is in the path of the translation stages.

  4. Connected the X Linear Translation Stage to the USB Hub by plugging the Mini-DIN to USB serial adapter into one of the Hub’s USB ports. You may need to use a cable extension to reach the USB Hub (Figure A-I.6).

    Figure A-I.6: Daisy Chaining the Linear Translation Stages.
  5. Daisy-chain the Y Linear Translation Stage to the X Linear Translation Stage. Connect the X Linear Translation Stage mini-DIN connector to the Y Linear Translation Stage mini-DIN connector using a Male-Female extension cable.

    • A daisy-chain connection will allow both X and Y Linear Translation Stages to be controlled from a single connection to the control computer, reducing cabling demands.

    • X and Y Linear Translation Stages share power. (Note: for larger X-Y Linear Translation Stages, a power supply needs to be connected to each device in the chain).

  6. Make sure that nothing is in the path of X and Y Linear Translation Stages. Connect the power plug of to the power connector of the X Linear Translation Stage. The green LED should light up indicating the unit has power (Figure A-I.7).

    Figure A-I.7: Translation Stage Connectors.
    Indicators:
    PWR (Green) - Power
    On Controller is operational
    Blinking at 2Hz The power supply voltage or device temperature is out of range
    Fading in and out slowly The device is parked
    ERR (Red) - Error
    On/blinking Controller has lost its settings, or an error has occurred. Please contact Technical Support
    MOT (Yellow) - Communication/Busy
    On Device Device is moving, or data is being transferred
    Blinking Device is under manual control via the knob (in Velocity mode). The blinking rate is proportional to movement speed
    Blinking at fixed rate Packet corruption has occurred for ASCII commands sent with a checksum
    ENC (Blue) - Slip/Stall
    On The device is slipping
    2 short flashes every 1 sec The stationary device has been forced out of position
    On-Off cycle every 2 sec The device has stalled and stopped

Grounding: To prevent damage to the device due to static buildup, the device should be properly grounded. Failure to ground the unit may result in the unit shutting down unexpectedly or ceasing to communicate with the computer. This problem can be minimized by not touching the unit during operation. If the unit fails due to static discharge, unplugging it and plugging it back in. Most Zaber devices are grounded via the shield wire of the data cables. This should normally provide a path to ground via the computer. For units which are being used without a computer, a ground lead should be connected to the chassis pin of the power supply connector.

Setting Translation Stage Parameters

Control computer can communicate to the translation stage through the USB connection for sending a command and getting a reply from it. NeoScan Mapping Utility program allows users to set the speed and the acceleration/deceleration time of the moving table and the direction of the scan. Make sure translation stage is connected to the USB Hub and then restart NeoScan Mapping Utility program.

Icon MAP.png
Open NeoScan Mapping Utility program by double-clicking on NeoScanMAP icon Icon MAP small.png on desktop Windows Explorer. Make sure the GPIB cable from back panel of lock-in amplifier and the USB cable from programmable motion controller are connected to the system.
  1. Press “Hardware Settings” tab in NeoScan Mapping Utility interface (Figure A-I.8).

  2. To set translation stage speed settings:

    1. From “Visa COM” serial port drop-down list select the COM port that the X Linear Translation Stage is connected to. A COM port is a specific serial connection on a computer, such as COM3.

    2. Set the speeds of translation stage from “Translation Speed” box (Figure A-I.8). The default value is 10 mm/s – indicating that translation stage can move 10 mm per second.

    3. Press “Set Speed” button to save the new settings. The system will respond with confirmation message “Set Speed OK” in information panel.

    4. The Scan Speed is ~ 0.3 mm/s.

    5. When translation stages power up, they need to be homed in order to get an accurate reference position. The home sensor is at the motor end of the stage. Press “Home Position” button. Make sure that nothing is in the path of X and Y Linear Translation Stages.

Figure A-I.8: Hardware Settings page in NeoScan Mapping Utility program.

Moving Translation Stage

To move translation stage to a defined position along the X-axis, enter the appropriate X coordinate in the X Position Setting Entry Box and then press “Move along X” button as shown in Figure A-I.9. Similarly, enter the appropriate Y coordinate in the Y Position Setting Entry Box and then press “Move along Y” button to move to the defined position.

Figure A-I.9: Setting X and Y position of translation stage (left), and setting the origin (right) in NeoScan Mapping Utility program.

As an example, in order to displace the translation stage to position X = +10 mm and Y = +6 mm – away from the origin (Figure A-I.10):

  1. Bring both X and Y translation stages to the HOME position. This is the origin X = 0, Y = 0.

  2. Enter a value of 10 (or +10) in X Position Setting Entry Box.

  3. Press “Move along X” button. The X translation stages will travel to location X = 10 mm.

  4. When the X translation stages reached at to location X = 10 mm, enter a value of 6 (or +6) in Y Position Setting Entry Box.

  5.   Press “Move along Y” button. This time the Y translation stages will move to location Y = 6 mm.

Figure A-I.10: Examples of the motion of the translation stage with respect to the HOME position.

Now that the translation stage is at location X = +10 mm and Y = +6 mm (away from the origin) in order to return to the origin (X=Y=0):

  1. Enter zero in X Position Setting Entry Box.

  2.   Press “Move along X” button. The X translation stage will travel to location X = 0 mm and Y = 6 mm.

  3.   Enter zero in Y Position Setting Entry Box.

  4.   Press “Move along Y” button. The Y translation stages will move to the origin (X=Y=0).

Alternatively, you could first enter 6 in Y Position Setting Entry Box and press “Move along Y” button and then enter 10 in X Position Setting Entry Box and press “Move along X” button.

  • “X Position” and “Y Position” in information panel indicates the current position.

Setting the Origin

The HOME position is considered to be the origin X = 0, Y = 0. In general, to set the origin

  1. Enter zero in X Position Setting Entry Box in “Hardware Settings” page in NeoScan Mapping Utility program.

  2.   Similarly, enter zero in Y Position Setting Entry Box.

  3.   Press “Set Origin” button (Figure A-I.9). The system will respond with messages in information panel.

To set X = 10 mm and Y = 6 mm as the new origin, assuming both X and Y translation stages are initially at the HOME position:

  1. Move the translation stage to position X = +10 mm and Y = +6 mm – away from the HOME position as discussed earlier.

  2.   Now the translation stage is at location X = +10 mm and Y = +6 mm:

    1. Enter zero in X Position Setting Entry Box.

    2.   Similarly, enter zero in Y Position Setting Entry Box.

    3.   Press “Set Origin” button.

If the origin is not the HOME position, one should check that each linear translation stage travels in the correct direction (positive or negative). As shown in Figure A-I.11, the positive X is direction away from the X stepper motor and the positive Y is direction away from the Y stepper motor. For example, assume that the point X = 10 mm and Y = 6 mm is the new origin (0,0). In order to displace the translation stage to position X = -5 mm and Y = -2.5 mm – away from the origin (Figure A-I.11):

  1. Enter a value of -5 in X Position Setting Entry Box.

  2.   Press “Move along X” button. The X translation stages will travel to location X = -5 mm.

  3.   When the X translation stages reached at to location X = -5 mm, enter a value of -2.5 in Y Position Setting Entry Box.

  4.   Press “Move along Y” button. This time the Y translation stages will move to location Y = -2.5 mm.

  5.   You can press “Move to Origin” button to go to the origin.

Figure A-I.11: Examples of the motion of the translation stage with respect to the new origin.

Setting the Scan Starting Point

There is no particular procedure to set the starting point of the scan. However, the following tips can be helpful for the users:  

  1.   Setup the DUT near the translation stage and the probe (which is inside the probe holder on plastic probe fixture).

  2.   The probe is extremely fragile. Make sure the probe head is far away from the DUT surface and any obstacle, so you have plenty of space to maneuver The probe breaks if hit with an object.

  3.   Make sure the DUT is placed on a flat and level surface. Use a level for a quick measurement. Alternatively, use the micrometer mounted on top of the translation table and measure the probe height from the surface of the DUT in its three corners – as shown in Figure 4.2.

  4.   Move both X and Y translation stages in such a way that the probe is positioned at the center of the DUT (if possible) as shown in Figures A-I.12 and A-I.13. You can do it manually using the Knob X and Knob Y or though the NeoScan Mapping Utility program.

    Figure A-I.12: Positioning the probe at the center of the DUT when the origin is at the HOME position.


    Figure A-I.13: Positioning the probe at the center of the DUT when the origin is not at the HOME position, but at point X = 10 mm and Y = 15 mm.
  5.   Use the Z Miniature Translation Stage (Micrometer) and a microscope or a powerful magnifier to adjust the desired probe height – the distance between the probe and the DUT surface. Record the micrometer reading.

    •   Make sure the crystal on the probe head does not hit the DUT surface. Here is a coarse estimate of how close the probe head is to the DUT surface. Illuminate the probe by the light from a desk electric lamp. Look into the microscope while lowering the probe. As the probe moves closer to the DUT, the probe shadow approaches the probe head (crystal), see Figure A-I.14.
    Figure A-I.14: A coarse estimate of how close the probe head is to the DUT surface.
  6.   Raise the probe far away from the DUT surface.

  7.   Set the scan area (No. Points. × Step Size) and choose the scan starting point (Figure A-I.15).

    Figure A-I.15: The scan starting and end points of a patch antenna.
  8.   Set the scan starting point as the origin. In order to do, move the translation stages around so that the probe is positioned at the origin and press “Set Origin” button (Figure A-1.16).

    Figure A-I.16: Setting the starting point of the scan.
  9.   Lower the probe to the desired height (recorded micrometer reading).

You are ready to scan. See sections 4.2.4 Scan Settings Page and 4.2.5 Scan Control Page for more details.

Appendix II: Troubleshooting

Low Power / No Power

If NeoScan optical mainframe is on;but the total return power and the polarization power are too low (Figure A-II.1) – or there is no power, then

  • Either the probe is not connected to Neoscan optical mainframe.

  • Or the probe is defective.

Therefore,

  1. Check the connectors.

  2. Inspect the probe.

  3. If the connection is fine and still there is no power, try another probe.

Figure A-II.1: NeoScan Optical Bench Manager indicating that the total return power is too low.

Low EO Signal / No Signal

If NeoScan optical mainframe is on, yet, the EO signal is too low or there is no signal (Figure A-II.2), then

  • The probe is not connected to Neoscan optical mainframe.

  • Or the probe is defective.

  • Or the cables are lossy or defective.

  • Or operating environment is too noisy.

Therefore,

  1. Check the connectors.

  2. Check the cables.

  3. Inspect the probe.

  4. If all the connectors and cables are fine, and still there is no signal, try another probe

Figure A-II.2: Spectrum Analyzer cannot detect any EO signal.

Missing NeoScan Program Icons

Icon all.png
NeoScan Program icons on desktop are missing.

NeoScan system control and monitoring programs including: NeoScan Optical Bench Manager (NeoScanOBM.exe), NeoScan Mapping Utility (NeoScanMAP.exe), and NeoScan Visualization Utility (NeoScanPlot.exe) are located in C:\Program Files (x86)\NeoScan. You can create a shortcut.

Lock-in Amplifier Not Found

If NeoScan Mapping Utility cannot communicate with lock-in amplifier or lock-in amplifier is not responding, then

  • Lock-in amplifier is off.

  • Or lock-in amplifier is not connected to the NeoScan system through the USB Hub.

  • Or GPIB address for lock-in amplifier Visa is not correct.

Consequently, the user is prompted with a warning message as shown in Figure A-II.3.

Figure A-II.3: Warning message when lock-in amplifier is not responding.

Therefore,

  1. Check whether lock-in amplifier is on.

  2. Or check if GPIB-USB cable from the (rear panel of) lock-in amplifier is connected to the USB Hub (Figure A-II.4).

    Figure A-II.4: Rear Panel of Stanford Research Systems SR844 RF Lock-In Amplifier.
  3. Press “Hardware Settings” tab in NeoScan Mapping Utility program. Put down the Visa menu and select the appropriate GPIB address for lock-in amplifier Visa The default is GPIB0::8::INST (See Figure A-II.5).

    Figure A-II.5: Setting lock-in amplifier parameters in NeoScan Mapping Utility.
  4. Disconnect the GPIB-USB cable from the USB Hub port and then reconnect it again to the same port.

If the problem persists, turn off lock-in amplifier and then turn it on. Then Disconnect the GPIB-USB cable from the USB Hub port and then reconnect it again to the same port.

  • It is important to note that failed to respond properly to this issue, it may cause the system hung up, in which you may restart the whole NeoScan system and control computer.

Translation Stage Not Responding

If NeoScan Mapping Utility cannot communicate with the translation stage system, then

  • The power is off.

  • Or the X Linear Translation Stage is not connected to the NeoScan system (USB Hub).

Consequently, the user is prompted with warning message as shown in Figure A-II.6.

Figure A-II.6: Dialog window when Translation Stage is not responding.

Therefore,

  1. Check whether the Linear Translation Stage power is on.

  2. Check if the translation stage cablings are correct.

  3. Check if the USB cable from X the Linear Translation Stage port is connected to the USB Hub.

  4. Disconnect the USB cable from the USB Hub port and then reconnect it again to the same port.

If the problem persists, turn off the programmable motion controller and then turn it on. Then Disconnect the USB cable from the USB Hub port and then reconnect it again to the same port.

  • It is important to note that failed to respond properly to this issue, it may cause the system to hung, in which you may restart the whole NeoScan system and control computer.

Translation Stage Has Hung Up

When the XY Linear Translation Stage hits the edge sensors of the base, it will hang up and stops functioning (see section A.4). In this situation,

  • Reset the Linear Translation Stages by switching it off and then turning it on,

  • Disconnect the USB cable from the USB Hub port and then reconnect it again to the same port.

Optimization Utility Program Not Functioning

NeoScan Optimization Utility program stops functioning if

  • The Lock-in Amplifier is off.

  • Or the Lock-in Amplifier is not connected to the NeoScan system through the USB Hub.

  • Or GPIB address for the Lock-in Amplifier Visa is not correct.

Consequently, information panel warns that spectrum analyzer “Not Found” as shown in Figure A-II.7.

File:Neoscanfig A II 7.png
Figure A-II.7: Dialog .

Therefore,

  1. Check whether the Lock-in Amplifier is on.

  2. Check if the GPIB-USB cable from the Lock-in Amplifier port is connected to the USB Hub (Figure AII-.8).

  3. Disconnect the USB cable from the USB Hub port and then reconnect it again to the same port.

File:Neoscanfig A II 8.png
Figure A-II.8: Cor.

Incorrect Working Folder (Directory)

Make sure NoeScan Mapping Utility or NeoScan Plot Utility programs are pointing to the correct working folder (Figure A-II.9).

Figure A-II.9: Correct working or project and folder path.
  1. In NoeScan Mapping Utility use the browse button to set “Working Folder” path to C:\Users\neoscan\Documents\NeoScan\Projects.

  2. In NoeScan Plot Utility use the browse button to set “Project Folder” path to C:\Users\neoscan\Documents\NeoScan\Projects.

Irregular Patterns in 2D Phase Plots

If there are irregular patterns in 2D Phase plots in NeoScan Plot Utility program, as shown in Figure A-II.10, it might be the case that there is no synchronization between scan instruments.

Figure A-II.10: An example of irregular pattern in 2D Phase plot when scan instruments are not synchronized.

Therefore,

  1. Make sure all 10 MHz reference cables are connected appropriately (in the back of the corresponding instruments) and the connectors are not loose.

  2. Check if the BNC cables are fine.

  3. Make sure “Modulation Generator” key in 100 MHz signal generator for lock-in amplifier is off.

Wiggling Power Levels

If the FC/APC connector is not clean (Figure A-II.11), despite probe optimization the return power and the optimization power graphs appears wiggling as shown in Figure A-II.12.

Figure A-II.11: FC/APC connector of a PM Fiber under microscope: A dirt seen as a black mark on the fiber end connector (left). A clean fiber (right).


Figure A-II.12: Wiggling return power and the optimization power graphs for a PM fiber with a dirt on the fiber end connector.

Therefore

  1. Detach the fiber connector from fiber port of the NeoScan system.

  2. Use a dry cleaning cloth (reel-based cassette cleaner) to remove dirt, dust, and oil from connector end faces (Figure A-II.13).

  3. Attach the fiber connector to the fiber port of the NeoScan system.

  4. Perform a probe optimization.

Figure A-II.13: Cleaning a connector end face using a dry cleaning cloth reel-based cassette cleaner

NeoScan Optical Bench Manager Program Not Responding

When the A/D and D/A convertor drivers are not detected by the system, NoeScan Optical Bench Manager program prompts a warning as shown in Figure AII-14. Or sometimes NoeScan Optical Bench Manager program does not respond.


Figure A-II.14: Warning massage for missing AD and DA addresses..

To solve the problem,

  1. Turn off the NeoScan system and turn it on again.

  2. Reboot the control computer.

  3. Go to Window Application (Program) or “Measurement Computing” folder and click on “Instacal” (Figure A-II.15).

    Figure A-II.15: Start the Instacal driver controller program.
  4. You may be prompted with a message box as shown in Figure A-II.16 saying that the previous board name has not been deleted. Press “OK” button.

    Figure A-II.16: Configure the Instacal driver controller program.
  5. The “Instacal” driver interface will list A/D and D/A board names – e.g. USB-1608FS board and USB-3114 (Figure A-II.17).

    Figure A-II.17: Instacal driver controller program list A/D and D/A board names.
  6. Select USB-3114 and double click on it.

  7. In USB-3114 Board Configuration window use the dropdown list and set at the D/A Ranges to +/-10V (default is 0-10V)as shown in Figure A-II-18.

    Figure A-II.18: Instacal driver controller program list A/D and D/A board names.
  8. Close “Instacal” driver interface and open NeoScan Optical Bench Manager program.

  9. If the “Instacal” driver interface does not list A/D and D/A board names as indicated in Figure A-II-19.

    Figure A-II.19: Instacal driver controller program cannot detect A/D and D/A converters.
    1. Double click on program “MCCRegistryFix3.exe”. You can find it in C:\ProgramData folder.

    2. Unplug the USB cable from the NeoScan Optical Mainframe.

    3. Plug the USB cable from the NeoScan Optical Mainframe.

    4. Run “Instacal” program again.