SIwave: Everything you need to know about the Compute Frequency Sweep Solver (HD version)

Hi, SI Wave is a power integrity and signals integrity tool. Compute frequency sweeps is one of the tools in SI Wave and it's the subject of this video. Compute frequency sweeps is used to study resonance in power planes.

It is similar to the resonant mode solver discussed in another video with a few differences. A frequency sweep solver detects resonance modes based on the physical dimensions and the effect of the source and the load.

With the help of the circuit tool, which will be discussed later on, it's part of the ANSYS electronic desktop, the frequency sweep solver injects the right voltage for each frequency based on the actual spectrum of the frequency.

The frequency sweep solver detects the signal that exists in real life. As a result, the frequency sweep solver can determine the magnitude of each resonance in the proper way, versus the resonant mode solver only relies on the physical dimensions only. Let's start.

It is not recommended to use SI Wave to build PCBs. Although this is possible, it's not the best way to use SI Wave. SI Wave can import CAD tools such as ANSYS ADB Translator for Allegro and Altium, IPC2581 for OrCAD, ODB++ files for Mentor Expedition, and board files for Cadence.

The ADB Translator can be installed on the ADB Translator. You can use the Card Tray to create styled panels. OrCAD users can build boards and Shanghai for data input local path. PSAC districts and remote education must now have Sydney's story and not the current images of Pi.

Changes to the ADB Translator are acceptable, but using IWax with a UMC server requires a long time. After importing the model, the next step is to add sources. SI Wave needs to know how and where each power plane net is excited.

In SI Wave, sources can be added in three ways: the DCIR setup or the net way, the manual way, and the component way. In the DCIR setup, the user must select a power plane or group of power planes and assign them voltage and current sources.

The voltage sources are assigned at the input, while the current sources are usually on the load side. For example, a voltage source can be selected at the output of the VRM, and a current source can be selected at the load.

It is important for the user of SI Wave to understand the concept of nets in SI Wave. When you upload your model, the model may have many nets, and some of these nets are connected in series using a component. If the component is a passive component, then you have what we call one passive link.

These two nets plus the passive component represent one passive link, but if it has an active component between the two nets, then these two represent two separated passive links. SI Wave can only solve passive links.

So you take one passive link and you put a voltage source on one side and you put a current source on the other side or you can put a voltage source on one side and a voltage source on the other side, but it has to be a passive link. And that's how you read your schematic.

You look for all the passive links that exist in the schematic. In this setup, we are assuming that at all frequencies, the voltage is 1.2, and the current source at the load is always 1 amp. So despite the fact that this is a DC setup, the same values will be used in the frequency sweeping.

Now we proceed to configure the simulation. This is simply allowing SI Wave to build the ports and do the necessary setup. Validate is to check the physical structure of your PCB. Make sure all the nets are well connected. There are no problems, disconnections, anything unusual.

As you can see, some of them SI Wave can fix. It seems that we don't have any problem in our PCB. Press OK. But we do not simulate because we are not interested in doing a DC analysis. We would like to do the frequency sweeping. We only use this setup to create our ports. So we can close this one.

Now let's look at the second way of defining ports, which is the manual way. From home, you select a voltage source and a current source. The problem with this approach is that the user must know where the source is as well as where the nearest ground is.

By selecting two points, SI Wave recognizes all the nets under these two points. So it's very important to select these two points in the proper way. Any layer can be selected. For this application, both the voltage and the ground are on the surface.

The third way of defining ports is the component way. From Tool, select Generate Circuit Element on Components. Select the part number, such as the VRM. Then you have to select the reference designator and the pins.

So in this case, it's pin 2 versus pin 4. We have to select the reference designation, so this needs to be 25. Let's choose this pin 1. Now we want to change it. This pin 2 is a richer value. So after this, we have the voltage source and the current source.

Now that we have our voltage source and current source, we can go to the simulation and start running our frequency sweeps.

We give it a name, a solution name, and notice here that you have two kinds of excitation: one using the source defined in the project, which are the voltage source and the current source, or there is the external way.

We're going to show how we're going to use the external way later on in this video. For now, we would like to use the ones defined in the project. And this is the band where we are looking for resonance, from 1 megahertz to 2 gigahertz.

In addition to that, we want SI Wave to plot the field for us, the voltage between the surface area, for example, between VCC and the ground below, because we are looking for resonance in the power planes that are located in the VCC layer and the ground layer.

Now that we have a solution, we go to the results and we have the frequency sweep one. The first thing we would like to do is view profile. This shows the solver timing and mesh used in each net.

Different models can be compared using this information, and from there, the user can make a decision whether he is satisfied with the Programming or he wants more long running can also be planned using this information.

That's why it's important to review the second thing is the view simulation properties. So in the future, if you would like to come back and learn about the setup that created this solution, you can select this option. You cannot change it, but you can take a look at it.

Now you know what kind of setup was used to generate this solution. Now we would like to see the results. So we select to plot surface voltages. The field can be plotted at any frequency on the selected layer. We selected to plot the field between VCC and the ground.

It's also possible to animate through all these frequencies. The scale goes up to 2.019, but the input, the injected voltage, is only 1. 2. This means that at certain frequencies, there are resonances. Run the animation and observe where the high values occur to detect these resonances.

We're looking for something that is yellow, orange, or red. Using this information, the user can place what we call voltage probes. As we're going to see later, notice here some values, high values, red values in this area. Now we know where to put our voltage probes.

The only way to do it is using the manual way. This is because the location of these voltage probes is not a pin or a connection between a net and a component. So you cannot use a net, you cannot use a component; it has to be done in a manual way. This is our voltage probe.

We will put a 1 here, so we set it between VCC and the ground probe 1. Let's put another 1 here, same thing, and the third one here. Now we can rerun the solver again using the same setup. So now we have a second solution, but this time we're going to plot the probe voltages.

Create plot, and this is the plot. See that's the beauty of having voltage probes. Now you can detect the location of all the resonance. The problem with this plot is that it assumes that at each frequency, we have 1.2 volts at the input and 1 amp at the output. As you know, this is not true.

What you need to know is what is the resonance when you are exciting your PCB with the real voltage value at each one of these frequencies.

To change it, we need the help of what we call customized sources, and these customized sources are implemented using the circuit tool in the ANSYS electronic desktop.

So in order to do that, we need to go back to SiWave and this time, this is going to be a piece of the code for Pseudon rad closer to the 이곶 and this time, we want to do what we call S-parameter solving. To do that, we go back to our orange icon and excite the PI analysis solver.

So the PI is the S-parameter solver in SI Wave. And we select our nets again and assign ports this time. Instead of assigning voltage sources, we assign just ports. We set the impedance to 0. 10. Configure, validate. Everything seems to be fine with the physical structure.

And this time, we will simulate. In the circuit tool, we will be using the transient solver. So don't forget to include the 0 Hz.

It's important to note that the maximum frequency, this one, number, affects the rising time number, which is here. 0.5 of our frequency is used to calculate the rising time. So we change this to 2 GHz. So the rising time now is around 250 picoseconds.

That's the minimum rising time we're allowed to use with 2 GHz solution. So these two points, these two numbers, are related. And we launch. Now we go to the electronic desktop and we create a new project and we call it frequency sweep. And we save this.

And we move that to the same directory where we have our SI wave. Save. Now we add a circuit. And we go here to symbols and we enter SI wave. So this is an SI wave link. So it's asking us which SI wave model or file you want to link to the circuit. We select this one.

Now it's asking us which solution. So we have two solutions. It's the first one that we want. It has two ports. Now we add a voltage source at the VRM site. And we're going to select a PRBS source. And we add a resistor at the end. And we add a resistor at the output.

And we add a resistor at the end. And we add a resistor at the end. Now we set up the input. Remember we said that our rising time should be around 250 picoseconds. Pulse width. Let's say we want pulse width to be around 500 picoseconds. The voltage should be 0.2 and not 1. 2. That's our noise.

Apply. OK. Then we add the transient solution. XM. Transient analysis. So the step here is related to the rising time. And the rising time is in picoseconds. So it's 250 divided by 10. Let's select 25 picoseconds. You can go even further.

The stop value is related to how many bits we would like to see. The longer this one, the better is the answer. We'll select 100 nanoseconds. OK. And we solve. See solution. Plot. 1. This is net number 2. And this is the ground is net number 3. Or the zero ground net.

So now we would like to display the results. And let's say Vnet 1, which is which is the input signal. As you can see, we have so many bits. 100111001 because it's in PRBS. We also would like to display the spectrum of this signal. So we go back. Same plot. This time we select spectral. Vnet.

And plot. So you see here it shows you. The spectrum contents. Of the signal. That's why the more the longer the more bits you have, the longer your simulation, the better the more accurate is your spectrum. The next step is to send back all this information back to SI wave.

The way to do that, you select this link. And you say push excitations. OK. Now if you go back to SI wave. And you select this solver. Notice what happens now. It automatically knows. That there is an external result coming from a circuit. It knows immediately.

Launching the solver with the same setup. Circuit. So we change the name. And we launch using the same setup. And we look at the signal. And we see that. The signal is coming from the same setup. And we look at the results again. Focusing on the probe voltages.

So now we go back to the electronic desktop. And we plot. The probes. Versus the spectrum of the signal. Make sure to set them up to the same scale. 50. 50 millivolts. Now you can see that this is a severe resonance. Because this is what we injected. This is what we are seeing. On the power plane.

Going back to SI wave. You can also plot. The surface voltage. Now we can animate through the different frequencies. Now notice that the values are very very very small. Because the input voltage is very small. And what you see here is the real thing. Because we are applying the right input voltage.

And the right output current. At all frequencies. Let's compare these results with the results from the compute resonant modes. This solver was explained in another video. So we will focus only on the results. So we launch the solver. And we start from. 1 GHz. To 2 GHz.

We want it to compute 30 modes. And we launch. Now we look at the results. So the Resonant Mode Solver provides a list of resonance. To find the critical ones. The user must scroll through them one by one. To do that. You need to solve for the field. Between the two layers of interest.

VCC versus ground. For all of them. Then you need to scroll through them one by one. 1 GHz. For all of them. The Resonant Mode Solver detects the resonance. At number 9. Which is 1. 268. So if we go back to the spectrum. We don't have 1. 263. We have 1.26 and 1. 27. And the resonance.

From the frequency sweep. Was detected as 1. 257. So there is a small difference between the two.

And that's the difference between calculating the resonance using only the physical dimensions, which is what the resonant mode solver is doing, or solving it using the physical structure plus the input and the output sources.