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In this tutorial, let’s talk about the basics of S-parameter simulation in ADS.

In the previous steps, we have created a subnetwork , placed inductors and capacitors, connected lines and grounded, set ports, and assigned them preliminary values. Now, we will draw the frequency response characteristics of the filter by learning S-parameter simulation.

Since the previous experiment did not name the test we wrote, we first rename it to “TestBench_MyFilter”.

Then, open the schematic and select “Simulations-S_Param” in the Library Palettes on the left side of the window to display all components that may be used in S parameter simulation.

Now, we choose to put in an S_Param controller. At the same time, since the circuit is not complete yet, we need to put in (TermG, used for terminal matching, the main function is to provide a standardized terminal load so that the port has correct impedance matching when performing S parameter simulation). And since the sub-design has two ports, we need to put in two TermGs and connect them.

The default value of impedance in TermG is 50 Ohm, which can also be defined as a value with parameters, such as , because here is impedance Z, not resistance R. In this design, we choose 50 Ohm for both the input and output loads.

Then, we define the parameters of the S_Param controller. Double-click with the left mouse button :

As shown in the figure, we can define S_Param Instance Name, which is currently SP1; we can select Sweep Type, which includes Single Point (simulation is performed only at a specific frequency point), Linear (linear, the frequency changes in linear steps, and simulation is performed at equal intervals between the set start frequency and end frequency), and Log (logarithmic, the frequency changes in logarithmic steps, suitable for simulations that need to span multiple orders of magnitude). Since this experiment is building a low-pass filter , we choose Linear ; we also need to define the Start/Stop frequency range, define Start as 0.01GHz, Stop as 0.5GHz, and Step size as 4.9MHz. You can choose the appropriate unit here, and set the number of frequency points in the simulation to 101 (it will be calculated automatically). The adjusted window is as follows:

Then, in the “Parameters” tab, we can select more simulation models, such as Y parameter simulation, Z parameter simulation, etc. Since delay is very important for the filter, we also select “Group Delay”.

Then in the “Noise” tab we can choose to perform noise calculations (if the circuit contains an amplifier, for example), but since calculating noise does not make sense for a filter circuit, we will disable it for now.

The modified S_Prarm controller is shown in the figure:

Save the design first (good habit: click Save every once in a while), then click in the toolbar or the shortcut key “F7” to perform automatic simulation. In the “Simulate – Simulations settings” at the top, we can set the simulation:

As you can see, the basic settings we need are already pre-filled.

After clicking Simulate, the following interface will appear:

The small window on the left shows some information about the simulation. If the design is wrong, an error message will be displayed. The large window on the right will be introduced in detail in the following tutorials.

Next article: ADS Tutorial (IV) Data Display