You couple two or more sources using the '''Port Definition Dialog'''. To do so, you need to change the default port assignments. First, delete all the ports that are to be coupled from the Port List of the dialog. Then, define a new port by clicking the '''Add''' button of the dialog. This opens up the Add Port dialog, which consists of two tables: '''Available''' sources on the left and '''Associated''' sources on the right. A right arrow ('''-->''') button and a left arrow ('''<--''') button let you move the sources freely between these two tables. You will see in the "Available" table a list of all the sources that you deleted earlier. You may even see more available sources. Select all the sources that you want to couple and move them to the "Associated" table on the right. You can make multiple selections using the keyboard's '''Shift''' and '''Ctrl''' keys. Closing the Add Port dialog returns you to the Port Definition dialog, where you will now see the names of all the coupled sources next to the name of the newly added port.
{{Note|It is your responsibility to set up coupled ports and coupled [[Transmission Lines|[[Transmission Lines|transmission lines]]]] properly. For example, to excite the desirable odd mode of a coplanar waveguide (CPW), you need to create two rectangular slots parallel to and aligned with each other and place two gap sources on them with the same offsets and opposite polarities. To excite the even mode of the CPW, you use the same polarity for the two collocated gap sources. Whether you define a coupled port for the CPW or not, the right definition of sources will excite the proper mode. The couple ports are needed only for correct calculation of the port characteristics.}}
[[File:PMOM51(2).png|800px]]
In a planar project with de-embedded sources, if you do not define any ports, the feed lines will simply be extended, and the exciting gap sources will be placed at the open ends of these extended lines. Note that if you define a de-embedded source along with a port definition in your project, then all the other port-assigned sources of your project must be of the same de-embedded type. You can define de-embedded sources for coplanar waveguides (CPW) on slot traces. To do so, you need to place two collocated, de-embedded sources with identical offsets (same phase reference plane), same source amplitudes but 180° phase difference. Note that for CPW structures, setting the number of Prony modes to 2 can get you more accurate results. In this case, the two extracted Prony modes will include the incident and reflected, odd and even, propagating modes of the CPW.
Â
=== Using the Line Calculator ===
Â
[[EM.Cube]]'s [[Planar Module]] provides a simple calculator for analyzing planar [[Transmission Lines|transmission lines]]. It is based on the frequency domain finite difference (FDFD) technique. You can find the characteristic impedance, effective permittivity and guide wavelength of a TEM or quasi-TEM transmission line defined based on your project's background structure. Therefore, any arbitrary stack-up configuration with any number of substrate layers can be considered.
Â
To access the Line Calculator, first you have to select a metal (PEC) trace or a slot (PMC) trace in the Navigation Tree. Right click on the name of a trace and select '''Line Calc...''' from the contextual menu to open the Line Calc Dialog. You can analyze a metal strip line on any PEC trace or a coplanar waveguide (coupled slot lines) on any PMC trace. The 2D line structure to be analyzed by the FDFD method consists of the background structure of your project with a metal strip or CPW located at the Z-plane of your selected trace. Depending on whether your open the Line Calc dialog from a metal trace or a slot trace, a picture of a microstrip line or a CPW line appear at the top of the dialog, respectively. In the former case, you have to specify '''Strip Width''' in the project units. In the latter case, you have to specify '''Slot Width''', too. Keep in mind that the strip width is equal to the spacing between the two slot lines minus the width of individual slot lines. Clicking the Analyze button of the dialog evokes the FDTD simulator, and calculated results are reflected in the boxes labeled '''Zo''', '''Effective Permittivity''' and '''Guide Wavelength'''.
Â
When your background structure involves a slot (PMC) trace, then there is an infinite PEC ground plane at the plane of the slot trace. In that case, when you analyze a strip line on a metal trace, you must keep in mind that your stack-up configuration will be truncated by the slot's ground plane just for purpose of Z<sub>o</sub> calculation. A typical case of this type is a slot-coupled patch antenna fed by a microstrip line underneath the slot. From the point of view of the Line Calculator, the microstrip line lies on a substrate layer that is backed by the slot's ground plane and it does not see the substrate layer lying above the slot plane.
Â
[[File:PMOM75.png]]
Â
Figure 1: Analyzing a metal strip line using the line calculator.
Â
[[File:PMOM76.png]]
Â
Figure 2: Analyzing a coplanar waveguide using the line calculator.
=== Short Dipole Sources ===
[[File:PMOM82.png]]
Â
== Working with Planar MoM Simulation Data ==
=== Visualizing Current Distributions ===