ADS Tutorial Momentum Simulation

In this section, let’s learn how to use Momentum Simulation. Momentum is an electromagnetic simulation tool used to simulate the electromagnetic performance of radio frequency (RF) and microwave circuits. It can be used to analyze transmission lines, passive components on circuit boards, and antennas.

In the previous section, we defined the stack-up of a typical microstrip configuration for a 20 mil Rogers substrate, and in the previous experiment, we constructed a microstrip structure.

Now, to set up an electromagnetic simulation in ADS , we need to mark the start and end points of our circuit. We can do this by selecting Insert Pins (one on the left and one on the right) from the toolbar:

At this time, we select the pin and can see the corresponding properties of the pin on the right side of the window, such as the metal layer to which it belongs, the pin type, the Net name, etc. When we import external files, we need to pay attention to the corresponding names of the material layers.

Then save our design, select “EM – Simulation Settings” in the toolbar or press the shortcut key “F6” to open the EM simulation settings. We name it “Momentum_EM” and select <None> for the template.

We can see that ADS provides a variety of EM simulation templates:

• @EMSETUP_SUPPLIED/Antenna: Electromagnetic simulation setup for antenna design. Antenna design usually requires specific simulation parameters to accurately simulate the radiation characteristics and performance of the antenna.
• @EMSETUP_SUPPLIED/MMIC: For electromagnetic simulation of monolithic microwave integrated circuits (MMIC). MMIC is a high-frequency electronic circuit, commonly used in radar, communication equipment and other fields. This template presets some parameters suitable for MMIC simulation.
• @EMSETUP_SUPPLIED/RFBoard: Used for electromagnetic simulation of RF Board. Electromagnetic interference and signal integrity issues need to be considered in RF board design. This template will configure relevant simulation parameters.
• @EMSETUP_SUPPLIED/RFIC: For electromagnetic simulation of radio frequency integrated circuits (RFIC). RFIC is used in wireless communication devices and involves complex high-frequency electromagnetic simulation. The template provides simulation settings suitable for RFIC.
• @EMSETUP_SUPPLIED/REMModule: For electromagnetic simulation of remote modules (REM Module). Remote modules may involve various communication and sensing applications. This template will configure appropriate simulation parameters to simulate module performance.
• <None>: Indicates not to use any preset template, but to use the factory default settings.

Then click “Create EM Setup View”. Since we changed the default name of the View, a prompt box will appear. We just need to select “Keep name to emSetup and Continue”. Then the EM simulation setup window will pop up. We have two momentum engines, one is Momentum RF, which is a quasi-static mode, and the other is Momentum Microwave, which is a full-wave mode. We choose the latter.

Then, we select “substrate” and we can see that we imported the correct substrate.

We select “Ports” and can see the pins and GND (an infinitely large plane) we defined previously.

In the “Frequency plan” we can define the frequency range of the simulation, set it from 0 GHz to 6 GHz, and set the maximum number of points to 101.

In “Options – Mesh”, we can mesh and decide how many elements are needed for each wavelength. Depending on the size of the circuit, we can increase or decrease it (for example, if we just want to simulate a spiral inductor, we can increase it to 100 or even 200). We can choose the default settings here.

Then click “Simulate” and we will start the EM simulation in the background. After the simulation is finished, the Data Display window will pop up automatically, and we can see that we have obtained a good low-pass filter:

The red points in the figure are the actual sampling points. EM simulation will obtain two sets of curves. The ones with “_a” are the results after adaptive fitting (blue curves), and the ones without “_a” are the results after linear fitting.

We can see that although we defined 101 points, the momentum simulation actually only uses 12 points to cover this frequency range (the type selected for the “Frequency plan” before was the adaptive type, which will complete the simulation as quickly as possible based on the actual situation. If a linear simulation is selected, 101 points will be simulated).

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