Viewing Tangential Electric Fields
The following feature requires a Current Density Viewer license.
Concept
Although Sonnet's EM solver is a full-wave simulator that accounts for the 3D electromagnetic fields in your circuit, it does not need to explicitly solve for the electric or magnetic fields to calculate the currents needed for accurate results. Thus, Sonnet does not provide full 3D electric and magnetic field plots.
However, there is a way to view the tangential electric field on a pre-determined xy plane. This is accomplished with a "Sense" polygon, which is a metal polygon located where you want to view the tangential electric field. It is set to a very high impedance so that it has little influence on the original fields in your circuit. The currents on the Sense polygon will be very small due to the high impedance of the metal, but will be proportional to the component of the electric field which is tangential to the xy plane. This is just a two-dimensional version of Ohm's Law: current is proportional to voltage.
Procedure
The following general procedure may be used to create a Sense polygon.
Create a Conductor Material with a high impedance.
We recommend using the Surface Impedance Loss Type and setting the Rdc value to 1e12 ohms/square. The electric field, in Volts per meter will be equal to the current density in amps/meter times the Rdc surface resistance value of 1e12 ohms/square.
Optionally, create a dielectric layer to place your Sense polygon.
The top or bottom of this dielectric layer should correspond to the location where you wish to view the electric field.
Create a Tech Layer which uses the Sense material.
This new Tech Layer should be located on the level where you wish to view the electric field. In addition, it should use Rectangular Meshing, and the Metal Model should be set to Thin Metal of any thickness (thickness is ignored for the Surface Impedance Loss Type).
For best results, use advanced meshing of the new Tech Layer.
In the Meshing section of the Tech Layer Properties dialog box, click the Advanced button and set X Max and Y Max to 1. This results in smoother current density plots at the cost of more computer resources. Depending on your circuit, you may need to use higher values of X Max and Y Max if using values of 1 requires too many computer resources to simulate.
Create a Sense polygon using the Tech Layer that you just created.
The polygon is usually a large rectangle. The larger the rectangle, the more computer resources will be required to simulate the project.
Enable the Compute Currents EM option.
The Compute Currents EM option may be found by selecting Circuit > Settings > [EM Options].
Analyze your project.
View your project's surface current density.
Select Launch > View Current. When the Current Density Viewer opens, select Plot > Response > JXY Mag Surface to ensure you are viewing the magnitude of the surface current density.
If you are not already viewing the Sense polygon's level, switch to that level now.
The current density is displayed. The electric field is proportional to the current density.
Click on the Sense polygon to see the current density in the status bar.
Multiply the current density by the surface impedance to obtain the electric field.
Example
The above procedure was used to create the example file, tane, which may be accessed using the Example Browser. In this example, a Sense polygon is placed above a microstrip gap. A 3D view of the current density shown below.
Strong fields can be seen across the gap.
In the initial 3D view, the Sense polygon will be completely blue because the auto-scale uses all metal levels to determine the scale. You will need to adjust the scale using Plot > Scale.
To obtain absolute values of the electric field, use the 2D view.
Use your mouse to click on the Sense polygon and read the value of the current density in the status bar. In this example, the Sense material has an Rdc value of 1e12 ohms/square. Multiply the current density by 1e12 to obtain the electric field in volts/meter.