ANSYS HFSS: Array Analysis Using The Array Factor Calculation

Hello, this is Ibrahim Nassar with OZEN Engineering. Today I'm going to show you an example of how to use the built-in array factor calculation within HFSS to perform different antenna array analysis. In this example, I'm going to use the ANSYS Electronic Desktop 2024 R2 release.

And to create the antenna geometry to perform the single element pattern simulation, I'm going to use the antenna design toolkit that is built-in with the ANSYS Electronic Desktop. To use the antenna toolkit, I can click on the Automation menu tab, then Show, Hide, Act Extensions.

Now you see the different tools. So we can click on the HFSS antenna toolkit. The geometry I'm going to use for this simulation is simple, basically a patch antenna. Let's select the one that is rectangular with a prop fit. And here we can select the center frequency.

So let's for example select 2.4 GHz. The material of the substrate, let's change it to a 4-4 epoxy. And now it's ready. So if we click on Synthesize, it will calculate the dimensions needed to be able to operate at 2.4 GHz center frequency.

And I'm going to adjust a little bit the substrate dimensions. So let's increase it by 2 cm, 8. 7. And the X and Y as well, 7. 4. And if you click now Finish, the toolkit will create the antenna geometry ready to simulate.

Now I'm going to close these Act Extensions to have a larger view and I'm going to expand this window. So this is the geometry. As you see, we cannot see the radiation air box because the toolkit uses a solution type that uses an auto-open region.

To change that, we can select the HFSS menu tab, Solution Type. And let's uncheck the Auto-Open Region option. Now I see the radiation air box. So I'm going to select it and delete it. And do some modification to the geometry before we do these simulations.

So these changes are really not necessary for this example. But I'm just going to show you also how to model periodicity and emulate that there are other elements exist nearby this entire single element. So let's go ahead and do that. Now we have the simulation. We have the HFSS element.

I'm going to create a different air box. And an easy way to do this is to select the substrate air box here, hit Edit, Copy. And Edit, right-click, Edit, Paste. And I'm going to change its dimension in the positive z-axis to increase it to about lambda over 4. So let's select 4 centimeters.

And let's select the object here. And we can quickly change the material here from 4 epoxy to vacuum. And let's change also the transparency to 0. 9. Now that we have this antenna geometry with the air box defined, we need to define a lattice pair to emulate the periodicity of this unit cell.

So to do that, I can right-click and say Selection Mode and select Phases. I can select this face. And then I'm going to select the face in front. Control key and click on it. Right-click, Assign Boundary, Coupled, Lattice Pair. Here we give it a name. And here we can define the scan angles.

But let's keep it here 0. So what this boundary is doing, it's enforcing the electric field to be similar on both faces with a phase delay or phase difference that you want. Now we're going to look at the broadside case. So we can define the scan angles to be 0 and hit Finish.

Now I'm going to select the same boundary on the other two faces. So let's select this face. Rotate the object and Control key and select this face. And right-click, Assign Boundary, Coupled, Lattice Pair. And let's keep the defaults.

From the top surface, I'm going to assign on the top surface, I'm going to assign the radiation boundary. Right-click, say Assign Boundary and Radiation. So now we should have everything ready to simulate. The solution setup gets created at 2.4 GHz, which is what we need.

So let's keep just the defaults. And the toolkit defined two frequency sweeps. So we don't need really two. Just look at one to make it quick. And here it's an interpolating sweep. So let's just reduce the frequency range to 1.4 and 3.4 GHz.

And let's increase the number of points to 201. Now we can save it somewhere. And then you can right-click and say analyze all. And it's going to start to simulate. While it's simulating, we can define an infinite sphere for the far field results.

And so let's right-click on radiation and insert the far field setup. And let's select an infinite sphere. Let's define the field from 0 to 360. And the theta from minus 180 to 180. And let's just keep the defaults.

So here let's look at the convergence by right-clicking on the analysis setup and select convergence. So it's converged. And now it's starting to do the frequency sweeps. Now the simulation is done. So we can double-click on this report to look at the return loss.

So you see it operates near 2.4 GHz. And now we can look at the far fields. To do that, we can right-click on results. And create a far field report. And let's look at the 3D polar plot. Let's select the directivity category. And the directivity total quantity. And the function to be dB. Okay.

And we can click new report. So this is the radiation pattern of the patch antenna, which is as what we expect. Let's create also a radiation pattern plot. And let's look at the radiation pattern. And same thing. Let's select directivity. Directivity total quantity. And the function to be dB.

Here we are going to be plotted at all the V angles. So let's just select the V zero degree angle. And hit new report. Okay. So this is the radiation pattern of the patch antenna at V zero, which is the X axis. So let's add a marker here just to know what is the value here.

So we're getting about 70 dB, which is the value of the radiation pattern. Okay. And we're getting about 70 dB, which is as what we expect. Now let's try to click on this trace and hit copy data. And try to click then on the plot and say paste. And I'm going to call it "no array factor".

So I did this so when we add an array factor we can see the change in the radiation pattern. Okay. Let's double-click on now on the design to be able to see the 3D model window. And let's create an antenna array.

To do that, you can right-click on radiation and say antenna array, antenna array setup. And here you have three options. The first one you use it if you don't want to define an array. Or if you have an array defined and you want to remove its impact from the far fields you selected.

The second one if you want to have a custom array setup and you just want to import it to here, to this interface, you can. And the third one you can create it using the HFSS, the HFSS array. Okay. And the third one you can create it using the HFSS tool. So let's select this option.

And let's click on array visibility so we can see the array elements how they are placed. Now let's define the array geometry. So we have now defined the center position and we have, you can define the directions and different three layout types. The rectangular, elliptical and linear.

So let's select the linear one. And let's go to the center position. And let's define the vector of it to be at the x-axis. So let's 1 and 0 and 0. And the center position to be 0. Here we define the design frequency. So let's select 2.4 gigahertz.

And now we can define the size of the array and the spacing in terms of absolute dimensions or in terms of wavelengths. So if we uncheck this we can define it now in physical dimensions. So let's make the length spacing 8. 7. Basically same as the substrate size along the axis.

And let's just have 4 elements to do that. So we can have that number to be at 26.1 which is 3 times this number. If we hit apply we can see now the change.

So you see now that the elements are presented with small spheres and they are different sizes because there are some array weighting applied here. To adjust that we can go to the array weight tab.

And here we can see that the array weight is now 0. And here as you see we have different aperture tapering functions. So we can let's select uniform to make it simple. And the scan condition definition let's look at just the broadside case for simplicity. Okay.

So now if we hit apply as you see we have 4 elements with equal phase and amplitude. Now if I hit okay the far field data will be updated and reflect the impact of this antenna array factor calculations. So if we go now to the 3D polar plot.

So you see now the radiation pattern got changed to what we expect from our 4 elements along the x axis. If we look at the radiation pattern plot. So you see now the gain went up to 13 dB which is a 6 dB increase. And that is what we expect when we have 4 elements.

Let's copy this trace as well and paste it here. So this is the array factor HFSS. Okay now let's activate again this interface and let's define the antenna array in the other way which is bringing it basically from importing it from a file. So we can select again antenna array, antenna array setup.

And let's select a custom array setup. And this again click on visibility so we can see it here. We can import the array setup so the HFSS text input as a text file. So let's click on import if you already have the file or let's create one here in this example so we can show you how to create it.

So let's select a notepad file. Okay. So here in this notepad file, basically, you have to define the number of elements. So let's have four. And then you have to provide the XYZ location of each element and the amplitude and phase.

So the first element let's make it at 0 0. Then you give a space for the second entry and 0. Then let's have a 1 volt amplitude and the zero degree. Now let's copy this and copy this. And then let's create a new one. So we have four rows now.

And the second one let's make it at 8. 7. The second one would be at 17. 4. And the third one at 26. 1. So if you don't provide dimensions here, HFSS will take the defaults. But you can also write it down so HFSS will take it as you want.

And then you can also create a new one and then you can also code it as you want. And then you can also create a new one and then you can also into this file. So let's call this centimeter cutters. This is centimeter cutters from four times on the x-axis and its visitors.

This area where so if you are using a ucm interface, you can save it. Click on you also that the counter if it's fine. Now if we go to each hand side here, you will have some info. Now just a business in this case, the center left here with thisboarding die. There you go.

Now open all of the tables, phase, and the number of cells. And as you see, it's reading the units. Okay, we hit OK and hit apply. So now you see how the array is defined. Yeah, here we did not center it around the origin, but that's fine. It's not going to show any difference in the far field data.

So we hit OK. And now we go and look at the radiation pattern. And as you see here, if we select this trace and this trace, the results will be identical as what we expect. That's all for this video. And thank you for watching.