{{projectinfo|Tutorial| Designing Distributed Bandpass Filters Using Coupled Transmission Line Segments |RF96RF101.png|In this project, the basic concepts of RF.Spice A/D are demonstrated, and you will build a simple voltage divider is modeled and examineddistributed bandpass filter using distributed coupled transmission line segments.|
*[[CubeCAD]]Coupled Transmission Lines*VisualizationEven Mode*[[EM.Tempo#Lumped Sources | Lumped Sources]]Odd Mode*[[EM.Tempo#Scattering Parameters and Port Characteristics | S-Parameters]] System Characteristic Impedance*[[EM.Tempo#Far Field Calculations in FDTD | Far Fields]] *[[Advanced Meshing in EM.Tempo]] Network Analysis|All versions|{{download|http://www.emagtech.com/contentdownloads/project-file-download-repository|EMProjectRepo/RFLesson7.Tempo zip RF Lesson 1|[[EM.Cube]] 14.87}} }}
=== What You Will Learn ===
In this tutorial first you will cascade several sections of generic coupled T-Lines to design a distributed bandpas filter. Then, you will realize a microstrip version of your distributed filter.
|}
Build a new circuit using a the Generic Coupled T-Lines device with Z<sub>0e</sub> = 70Ω, Z<sub>0o</sub> =30Ω and len = 37.5mm. Use use two Net Markers to designate the input and output ports. Leave Ports 2 and 3 of the device X1 open as shown in the above figure.
Run a Network Analysis Test of your circuit with the parameters specified in the table below. Make sure to uncheck the "Decibels" checkbox.
Run a Network Analysis Test of your circuit with start and stop sweep frequencies set to 1GHz and 3GHz, respectively, and a linear frequency step size of 1GHz. Check only the {| border="Table0" checkbox and uncheck the |-| valign="Graphtop" checkbox. In the ||-{| class="Outputwikitable" tab of Network Analysis Test Panel, choose |-! scope="Zrow" [[Parameters]] options with | Start Frequency| 1G|-! scope="Realrow"| Stop Frequency| 3G|-! scope="row"| Steps/ImagInterval| 1G|-! scope=" format. Make sure to uncheck the row"Decibels| Interval Type| Linear|-! scope=" checkbox. The simulated row"| Parameter Set| Z|-parameter results are compared to their analytical values in the table below: ! scope="row"| Preset Table Plots| Cartesian (Real/Imag)|}
The simulated Z-parameter results are shown below and then compared to their analytical values in the second table:
<table>
<tr>
<td>
[[File:RF95.png|thumb|600px|Real and imaginary parts of the Z11 and Z21 parameters of the open-circuited Generic Coupled T-Line two-port.]]
</td>
</tr>
</table>
{| class="wikitable"
|}
== Designing a Coupled Line Bandpass Filter ==
Before closing In this section, run another Network Analysis Test part of your circuit with the same port assignments. But this time tutorial lesson you will calculate the Scascade four quarter-[[parameters]] over a wider frequency range from 500MHz wavelength Generic Coupled T-Line segments to 3.5GHz with build a linear frequency step size of 10MHzdistributed bandpass filter as shown in the opposite figure. Choose Port 1 of the "S" [[Parameters]] option with Amplitude-Only Cartesian graph typefirst segment and Port 4 of the last segment are designated as the input and output ports. Check Port 4 of each segment is fed into Port 1 of the "Decibels" checkbox once againnext segment. The insertion loss (|s21|) Ports 2 and return loss (|s11|) results 3 of all coupled line devices are shown in left open-circuited. Proper grounding is done for all the figure below: negative pins.
<table>
<tr>
<td>
[[File:RF97RF96.png |thumb|750px580px|Graph of S11 and S21 parameters The schematic of the open-circuited Generic Coupled T-Line two-port over the frequency range 500MHz-3.5GHzgeneric coupled line bandpass filter.]]
</td>
</tr>
</table>
<table><tr><td>[[File:RF95.png|thumb|560px|Real and imaginary parts of the Z11 and Z21 parameters of the open-circuited Generic Coupled T-Line two-port.]]</td></tr></table> [[File:RF96.png|thumb|550px|The RF.Spice schematic of the generic coupled line bandpass filter.]] == Designing a Coupled Line Bandpass Filter == In this part of the tutorial lesson you will cascade four quarter-wavelength Generic Coupled T-Line segments to build a distributed bandpass filter as shown in the opposite figure. Port 1 of the first segment and Port 4 of the last segment are designated as the input and output ports. Port 4 of each segment is fed into Port 1 of the next segment. Ports 2 and 3 of all coupled line devices are left open-circuited. Proper grounding is done for all the negative pins. The following table gives the [[parameters]] of each coupled line segment:
{| class="wikitable"
|-
|}
All the segment lengths are chose to be len = 37.5mm, which is a quarter wavelength at the center frequency of the filter f<sub>o</sub> = 2GHz. TEM transmission lines with ε<sub>eff</sub> = 1 are assumed. The impedances have been chosen to achieve an equal-ripple bandpass filter design.
All the segment lengths are chose to be len = 37.5mm, which is a quarter wavelength at the center frequency of the filter f<sub>o</sub> = 2GHz. TEM [[Transmission Lines|transmission lines]] with ε<sub>eff</sub> = 1 are assumed. The impedances have been chosen to achieve an equal-ripple bandpass filter design. Run a network analysis of this two-port circuit. Set the start and stop frequency of the sweep to 1GHz and 3GHz, respectively, with a linear step of 10MHz. Generate an amplitude-only, Cartesian graph of the S-[[parameters]]. The figure specified below shows the graph of s11- and s21 [[parameters]]. Note that a linear scale is used for frequency. The filter has a center frequency of f<sub>o</sub> = 2GHz with a 3dB bandwidth of about 235MHz. The response drops to -45dB at 1.5GHz and 2.5GHz.:
{| border="0"
|-
| valign="bottomtop"|[[File:RF98.png |thumb-{|800pxclass="wikitable"|left-! scope="row"| Start Frequency| 1G|Graph of s11 and s21 parameters of the distributed Generic Coupled T-Line filter over the frequency range 1GHz! scope="row"| Stop Frequency| 3G|-3GHz.]]! scope="row"| Steps/Interval| 10Meg|-! scope="row"| Interval Type| Linear|-! scope="row"| Parameter Set| S
|-
! scope="row"| Graph Type
| Cartesian (Amplitude Only) with Decibels
|}
The figure below shows the graph of S11 and S21 parameters. Note that a linear scale is used for frequency (the bottom axis). The filter has a center frequency of f<sub>o</sub> = 2GHz with a 3dB bandwidth of about 235MHz. The response drops to -45dB at 1.5GHz and 2.5GHz.
== Realizing a Microstrip Version of the Coupled Line Bandpass Filter==<table><tr><td>[[File:RF99RF98.png|thumb|580px750px|The RF.Spice schematic Graph of S11 and S21 parameters of the coupled microstrip bandpass distributed Generic Coupled T-Line filterover the frequency range 1GHz-3GHz.]]</td></tr></table>
In the last part of this tutorial lesson, you will design and test a microstrip realization of the coupled line bandpass filter you simulated in the previous part. For this purpose, you will use a substrate of thickness h = 1.6mm with ε<sub>eff</sub> = 3.4. You will assume a lossless substrate (tand Designing Two Sets of Coupled Microstrip Lines = 0). Remember that in the previous section, TEM line segments with ε<sub>eff</sub> = 1 were assumed and the length of the coupled line segments were set to be a quarter free-space wavelength at 2GHz. For this part, first you need to design couple microstrip lines with the given even and odd mode impedances. Then, you have to calculate the guide wavelengths of the couple microstrips at 2GHz. You will do these using [[RF.Spice]]'s Device Editor.
Open In this part of the "Coupled Microstrips Designer" dialog from the RF Menu tutorial lesson, you will design and test a microstrip realization of Device Editor. Enter the coupled line bandpass filter you simulated in the previous part. For this purpose, you will use a substrate [[parameters]]: of thickness h = 1.6mm and er with ε<sub>eff</sub> = 3.4. Enter the Z0e and Z0o values for the two types of coupled line segments from You will assume a lossless substrate (tand = 0). Remember that in the previous section and calculate width and spacing of the coupled microstrip lines for each case. Then, open the "Coupled Microstrips Calculator" dialog from the RF Menu of Device Editor. Enter the calculated microstrip width and spacing values to verify your design and also find the corresponding guide wavelengths TEM line segments with &lambdaepsilon;<sub>geff</sub> at 2GHz. The lengths = 1 were assumed and the length of the coupled microstrip line segments are chosen were set to be a quarter of the corresponding guide free-space wavelength at 2GHz. The following table summarizes the [[parameters]] of the For this part, first you need to design coupled microstrip segments L1, L2, L3 lines with the given even and L4odd mode impedances. Then, you have to calculate the guide wavelengths of the couple microstrips at 2GHz. You will do these using RF.Spice's Device Manager.
Open the '''Coupled Microstrips Designer''' dialog from the Tools Menu of Device Manager. Enter the substrate parameters: h = 1.6mm and er = 3.4. Enter the Z0e and Z0o values for the two types of coupled line segments from the previous section and calculate width and spacing of the coupled microstrip lines for each case. Then, open the '''Coupled Microstrips Calculator''' dialog from the Tools Menu of Device Manager. Enter the calculated microstrip width and spacing values to verify your design and also find the corresponding guide wavelengths λ<sub>g</sub> at 2GHz. The lengths of the coupled microstrip segments are chosen to be a quarter of the corresponding guide wavelength at 2GHz. The following table summarizes the parameters of the coupled microstrip segments L1, L2, L3 and L4.
{| class="wikitable"
|}
<table>{| border="0"<tr>|-| valign="bottom"|<td>
[[File:RF100.png|thumb|360px|left|RF.Spice's Coupled Microstrips Designer dialog.]]
| valign="bottom"|</td><td>
[[File:RF102.png|thumb|360px|left|RF.Spice's Coupled Microstrips Calculator dialog.]]
|-</td>|}</tr></table>
== Realizing the Microstrip Version of the Coupled Line Bandpass Filter==
Build your microstrip circuit using four "Coupled Mirostrips" parts with the [[parameters]] specified in the above table. You can access the part from '''Menu > Transmission Lines > Physical Transmission Lines > Coupled Microstrips'''. Connect them the four parts in a cascade cascaded fashion as shown in the opposite figure. Run a network analysis of this two-port circuit. Set the start and stop frequency of the sweep to 1GHz and 3GHz, respectively, with a linear step of 10MHz. Generate an amplitude-only, Cartesian graph of the S-[[parameters]]. The graphs of s11- and s21 [[parameters]] are shown in the figure below and agree perfectly with the results of the previous section.
<table>
<tr>
<td>
[[File:RF99.png|thumb|620px|The schematic of the coupled microstrip bandpass filter.]]
</td>
</tr>
</table>
Run a network analysis of this two-port circuit with the same parameters as in the previous section:
{| border="0"
|-
| valign="bottomtop"|[[File:RF101.png |thumb|800px|left|Graph of s11 and s21 parameters of the Coupled Microstrip bandpass filter over the frequency range 1GHz-3GHz.]]
|-
{| class="wikitable"
|-
! scope="row"| Start Frequency
| 1G
|-
! scope="row"| Stop Frequency
| 3G
|-
! scope="row"| Steps/Interval
| 10Meg
|-
! scope="row"| Interval Type
| Linear
|-
! scope="row"| Parameter Set
| S
|-
! scope="row"| Graph Type
| Cartesian (Amplitude Only) with Decibels
|}
The graphs of S11 and S21 parameters are shown in the figure below and agree perfectly with the results of the previous section with the generic coupled T-Lines.
<table>
<tr>
<td>
[[File:RF101.png |thumb|750px|Graph of s11 and s21 parameters of the Coupled Microstrip bandpass filter over the frequency range 1GHz-3GHz.]]
</td>
</tr>
</table>
<p> </p>
[[Image:Back_icon.png|40px]] '''[[RF.Spice_A/D#RF.Spice_A.2FD_Tutorial 2FD_Tutorials | Back to RF.Spice A/D Tutorial Gateway]]'''