Where To Find This Example
AWR Version 15
AWR Version 14
Different Port Types in EMSight
This project is intended to demonstrate how to use the three different port types available in EMSight, edge ports, via ports and internal ports. The edge port is the most common and most intuitive. The via port is second in ease of understanding what it does. The internal port is the most difficult to understand. This demonstration will show the simple example of where a user wants to simulate a capacitor sitting between two microstrip lines.
Many times designers want to be able to insert a model internal to an EM simulation. There are several ways to do this that utilizes different ports in EM Sight. If you can easily break the circuit into two pieces then this will be the easiest and most straightforward. You can then piece together the two EM halves and the model to go in between in a schematic. When using edge ports, a shape must touch the edge of the enclosure to be able to put a port on it. You can then select the port and drag the port reference plane to de-embed off the effects of the enclosure. We recommend de-embedding two substrate heights or two line widths, which ever is greater.
If you cannot break the EM structure into pieces you can use via ports or internal ports. When you use via ports (place a via port by clicking the "Via" radio button under "Drawing Layers" first and selecting Draw > Add Via Port from the menus) it is just like drawing a regular via and it is modeled just like a via. The only difference is that the end of the via touching the enclosure must be grounded. One common mistake people make is that they put regular vias and via ports that touch. If you do this, the via port will be shorted. When simulated, the via port will simulate just like a via. If you want the reference plane to be at the top side of the via, the via must be de-embedded. We don't currently have an automatic way to de-embed. This example will show how to do to de-embed manually.
Your final option is to use an internal port. You can place an internal port by selecting Draw > Add Internal Port. You can only add an internal port to the edge of a shape and the shape must be selected first. An internal port should go between two touching polygons. The internal port will break the connection between the touching polygons and put the positive end of the source on the side with the + symbol in the EM structure. The negative end of the source is the other side of the port. This port is different in that the edge and via ports' ground are the EM structure enclosure.
The graphs in this project are showing the magnitude and angle of the complete circuit simulated on rectangular plots and s11 on a smith chart.
"Edge Ports": This schematic shows the circuit where the input line and output line are separate EM structures and the schematic is used to piece the circuit together.
"Via Ports Deembedding": This schematic shows the circuit where the input and output lines are simulated in one EM structure and via ports are used to insert the capacitor into the EM simulation. The negate element is used to de-embed the inductance of the vias in this simulation. The negate model is negating an EM simulation of just the vias. The EM subcircuit with the negate element on the via ports brings the reference plane back to the top of the EM simulation.
"Via Ports No Deembedding": This schematic is identical to Via Ports Deembedding except the negate elements are not included. This is to show that the effect of the vias is signification at higher frequencies but probably can be ignored at lower frequencies. Please see that the response for this network deviates from the others at about 1 GHz.
"Internal Port": This schematic shows the circuit where the input and output lines are simulated in one EM structure and an internal port is placed where the capacitor should go. The internal port only generates one additional port for the subcircuit. To connect a component across the internal port, one end of the component is connected to the exposed port and the other is connected to ground. Note, this ground should be a unique ground, not one shared with other ground locations in the circuit. The ground here tells the simulator to hook the component across the internal port.
EM Simulation Comments:
In order to get these results to match well, each enclosure was made the same size. This will rule out any enclosure effects as the difference between simulation results. Remember that in EM Sight, the sidewalls are prefect electric conductors and if structures are too close, the EM energy can couple to the sidewalls causing erroneous results.