EM.Cube FAQ
EM.Cube FAQ
Questions/Answers
What formulae are used while calculating the radiation patterns, and other parameters like gain, directivity
The Far-Field Approximation for Radiation & Scattering Problems at:
what is meant by LCS settings?
EM.Cube provides a number of different coordinate systems. The two most important ones are the World Coordinate System (WCS) and the Local Coordinate System (LCS). Every object has a Local Coordinate System that determines the location of the object in the world coordinate system and its orientation, i.e., its rotation angles with respect to the world principal axes. The center of the local coordinate system is the most important characteristic point of an object. The position of the LCS center varies among different object types. For example, the LCS center of a box is the center of its bottom face, while the LCS center of a sphere is its true geometrical center. The LCS has three local X-, Y-, and Z-axes. For most objects, these axes line up with the object's natural axes. For example, the local Z-axis of a cylinder or a cone is always aligned along its geometrical axis. For further information please see the "Local Coordinate System" section at:
How can we include different materials/metals and their properties in predefined arrays?
For simplicity, in our tutorials we use wizards to create antenna for a project. However, one can starts project from scratch and include different materials/metals with their properties in their design and then use the "Array Tool" from the tool bar to create an array. We may not need to use wizards for a complicated design.
How do we change the element spacing in line arrays?
If you start your project from scratch and use "Array Tool" to create say a 3 x 3 array with 5 mm spacing, simply set Element Count for X, Y and Z to 3, 3 and 1 respectively, and Spacing to 5, 5, and 0 for X, Y, and Z respectively, in Array Properties dialog window as indicated in the attached figure.
However, if you use a wizard, the Spacing might be parameterized in terms of other variables. For instance, in EM.Libera's Tutorial Lesson 2, In in Array Properties dialog window the Element Count for X, is expressed as direct_spacing_lambda and X Spacing is defined in terms of n_direct. To change X Element Count = 50 and X Spacing = 7 you may simply replace n_direct with 7 and direct_spacing_lambda with 50.
Alternatively, it is suggested, to keep n_direct and direct_spacing_lambda in the Array Properties dialog window untouched, yet, change their values from the Variables dialog window.
What is a good way to draw a surface with a curve of y0 * exp(r*x) where I can run a parametric study of r? Again drawing parametric curves and then fill fixed the design.
You can use "Taper Strip Tool" and check mark the "Exponential" check box.
I have been using EMCUBE on my new workstation. I just realized that the wizards (e.g., the wire dipole wizard) are not active. If I remember correctly, I faced this issue previously and it was because one of the folders were missing (the folder with the python based wizards I think). I don't have that folder anymore.
. There are few updates that were not included in the link EMCUBEfiles.zip we sent you on February. Therefore, we include them in EMCubeNewWiz.zip file that can download it from the following link:
http://www.emagtech.com/downloads/EMCubeNewWiz.zip
1. Please Unzip EMCubeNewWiz.zip file. It contains three folders Models, Python, and Wizards. 2. Copy or move the new Models, Python, and Wizards into C:\Users\username\Documents\EMAG folder let it overwrite the existing ones.
Kaz has mentioned that you have problem with plot function while trying to plot for the second time. You cannot have more than one PyPlot graph window open at one time. For this reason an error window pops up indicating "Another PyPlot window ... is already open. Please close ..." In other words, you have to close the 1st PyPlot graph window before plotting another graph or running the simulation.
Nonetheless, sometimes the PyPlot window will buried or concealed under other windows. Please make sure to bring the PyPlot window up/front and close it before plotting another data set.
The advantage of using PyPlot is that allows you to plot two data set files (with same type, e.g. .CPX) in the same PyPlot graph window as shown in the attached figure. You can have two instances of EM.Cube program and each have independent PyPlot graph windows.
I read from your website that your software can determine k-beta diagram of periodic structures which is commonly called DISPERSION DIAGRAM. Do you have any model for that purpose? I searched periodic structures and could not find any model.
To determine k-beta diagram of periodic structures, you can follow our EM.Tempo Tutorial Lesson 8: Analyzing A Periodic Frequency Selective Surface:
and select "Dispersion Sweep" from the Run Simulation window as indicated in the attached figures (KBT1a.png and KBT1b.png). Attached please also find a sample project (KBT1.zip). Please unzip KBT1.zip and run the simulation. You may plot "despersion_sweep_reflection.DAT" and "despersion_sweep_transmission.DAT" from the Data Manager.
How can I import my own radiation patterns in Terrano *.rad where I have for each antenna in the transmitter and receiver both the co-polarized and cross-polarized radiation patterns? Also, do you have the manual of Terrano?
. To import a radiation patterns (*.rad) in EM.Terrano open the property dialog of the transmitter set (or receiver set) and select the radio button labeled User Defined Antenna Pattern as the radiator type. Then click the Import button of the dialog. The Windows standard Open dialog opens up with the file type set to ".RAD". Browse your folders to find the downloaded pattern file. Select it and click the Open button. You will see the path of the downloaded file in the box next to the Import button.
Please see the Importing External Antenna Radiation Patterns for the Transmitter & Receivers section in EM.Terrano Tutorial Lesson 8: Simulating A Communications Link With Directional Antennas: http://www.emagtech.com/wiki/index.php/EM.Terrano_Tutorial_Lesson_8:_Simulating_A_Communications_Link_With_Directional_Antennas#Importing_External_Antenna_Radiation_Patterns_for_the_Transmitter_.26_Receivers You can view EM.Terrano Manual from the following link: http://www.emagtech.com/wiki/index.php/EM.Terrano
All information on EM.Cube can be found from EM.Cube Wiki page http://www.emagtech.com/wiki/index.php/EM.Cube
1. Picasso: Is it possible to define Vias that go through more than one layer ?
You can define Vias' for each layer in such a way that they are positioned/located on top of one another and are exactly the same.
2. Why loss tangent is not automatically specified for known commercial materials, e.g. RO4003C ?
Thank you for bringing it into our attention. We will add it in the next released version.
3. Is it possible to Copy and object together with rotation/mirror ?
Mirror operation keeps the original object and create a new one. Yet, in rotation the original object will change. For this reason you may copy and the rotate the copied object.
4. Can EM-cube support metal surface roughness (this is crucial for high microwave applications) ?
We do not have a parameter for the surface roughness in EM.Picasso. However, there is a relation between the surface roughness and the effective conductivity. You can use "Conductive Sheet Traces" with the effective conductivity. and rms height instead of "PEC Traces". We will add this option in the next release.
1) How do I write the Python Code for my own objects and add it to the simulation? Is it possible to access some part of the code for reference?
The following link provide an example how to write a Python script
Here is a more detailed information on Using Python to Create Functions, Models & Scripts
http://www.emagtech.com/wiki/index.php/Using_Python_to_Create_Functions,_Models_%26_Scripts
2) For modelling of wired antennas, I have used thin wires for respective elements. How will I consider the geometry of a thin wire for calculating current densities in each element? Also, do I have to take only thin wires or while modelling wired antennas or will cylindrical structures do?
In EM.Libera, if you open up he Thin Wire dialog, in the property dialog, you can change the define the wire radius from "Wire Radius" box. In other words, it’s a tiny cylinder with small radius of "Wire Radius."
Please see "Constructing the Wire Dipole Antenna Geometry" section in the EM.Libera Tutorial Lesson 1: Analyzing A Center-Fed Wire Dipole Antenna
3) What exactly is the function of a 'Port Definition'? How is it used in calculating the antenna parameters?
Ports are defined to calculate the scattering, impedance and admittance parameters of a one-port or multiport structure.
Port Definition Observable
Graphing Port Characteristics & Other Complex-Valued Data
4) How do I use the 'Wire gap circuit source' in between two thin wires? If it is not possible, is there any other method of excitation?
A wire gap source must always be associated with an existing line object in the project workspace. Please note that when you define your line object say 150 mm, the wire gap source creates an infinitesimal gap on the line, i.e. create two lines of 75 mm length, and connects a voltage source across the gap. All happens behind the scene. Please look at Examining the Gap Source & Simulation Observables in Lesson 1
1. How do i set simultaneous excitation of multiple ports ?
2. Can i use amplitude of -1 in order to create a 180 phase shift between ports in the FDTD simulation ?
otherwise, how can i stimulate 2 ports with 180 degrees phase shift ?
3. Can i choose some ports to be stimulated and others with no stimulation (just as a termination) ?
You can define multiple sources that will set the corresponding ports. In EM.Cube amplitude of the source should not be negative. For this reason, in order to introduce phase shift of 180 deg., you can click on "Waveform..." button in the "Source Properties" section of a Source dialog window. In the "Excitation Waveform" dialog window, set the Amplitude to 1 and the Phase to 180. Similarly, by setting the Amplitudes of some sources to 0 (zero) you can let some ports to be stimulated while those with zero amplitude without any stimulation (terminated).
To calculate S11-S12, you can do post-processing by getting them into Python. You can perform some operations (add, subtraction ...) on RCSs, Radiation Patterns, Field Sensors, etc. Yet, we do not have any Python function for S-parameter operations. We will implement some new Python in the next EM.Cube release.
