Radiated Emission Simulation of PCB Inside An Enclosure & Connected To A Cable Using ANSYS EMC Plus

Radiated Emission Simulation of PCB Inside An Enclosure & Connected To A Cable Using ANSYS EMC Plus Hello, this is Ibrahim Nassar with Ozen Engineering.

In this demo, we will be using the ANSYS EMC Plus tool to simulate the radiated emissions of a PCB placed inside an enclosure and connected to a cable. This demo is part of the ANSYS EMC Plus tutorial examples.

We will start this demo by opening an EMC Plus design that contains this geometry, which is basically a ground plane here and an enclosure here, which is in this case, it's like a PCB case. And then there's a connector and through the connector, there's a cable.

So to select the top face of this enclosure and we can right click and select hide. And you see here that cable runs inside the enclosure and here we're gonna bring the PCB file and place it here.

To import the PCB files we can go to the EMA3D tab here and click on this button which shows the EDB import. The EDB is kind of the file format that ANSYS is using to translate PCB files into the ANSYS tools. Click on the bottom of the screen.

Then, if we click here on these three dots, we can navigate to the location of that EDB file, which is here. And we click open. And now it's placed here, so we can move it around. So we want to place it basically here, near these conductors.

But before that, we want to kind of do some filtering to remove many of the nets that we don't need for this simulation or just to simplify the model. Click on the three dots to select one of the nets and click on the keyboard and control A to select them all.

We just want to keep two nets, which is this one and the ground one here for this example. And now I want to click on delete to delete all the others. So these are the two nets that we want to keep. Then we click OK. We're also going to remove all the components, so clear and hit OK.

So now we want to move basically this site, we can use these arrows or we can go here and put exact dimensions. If we click on Settings, Origin, we're going to change the X location to be minus 80, the Y location to be minus 30, and the Z location to be 6 millimeters.

Click on the green check mark and the file is going to be imported. Now we see that the file is being imported here and we see now the library of materials is showing up which shows that we have only copper and a far for epoxy for the substrate.

If we zoom in here, we should see these wires connected to these two pads. Here we are going to assign an excitation later and do the radiation emission analysis. Now the geometry is imported. Next we are going to assign the materials.

Assign the materials for these conductors and all the other objects. Assign the materials for these two wires. To do that, go to EMA3D tab and select Materials. Select PEC. Now we have three options for the material selection. We have 3D objects or surfaces and lines.

So here we want to select these two lines. We want to select, click here. Then we want to select the first line and we can also click on the second one. So now both are selected and we click on the green checkmark.

And we can verify now that these two wires are assigned as PEC by going here Now we can go to the material library and assign the material for the enclosure and the other objects.

We can go to materials and click isotropic and we can define a material or use the material library to select one of these materials but here we're going to let's define one to be aluminum AL and we click on general we can give it a color so let's give it like a gray and we want to change the conductivity to be 1.9 e7 Now we want to select these objects, so we can go to this Select Bodies and here we can select it from the project tree here.

So let's expand the EMC enclosure and we want to assign it to the enclosure. Click on the cable connector and select the fastener and the ground plane and wall connector. Click on the green checkmark.

Similarly we can go here select this material from the libraries to see what is being selected So now we completed the material assignment Okay, so now we want to assign the shield to the conductor that runs between the connector all the way to this electric wall, but not inside.

To do that, we go to the M-Harness tab and we click on cabling and we select the shield. We go to the line selection mode and we want to select where we want to apply the shield which will be to this wire from the connector all the way to the electric wall but not inside the connector.

And next we want to define where this will be terminated so to do that we go to the point, select a point and we want to select this point so you see it get highlighted and this point. Now the tool understands that the shield will be just between those two points.

Next, we want to set the properties and the size of the shield. To do that, we click on Library. And we can go to the library here of all the definitions. And we want to select TSP, Twisted Shield Pair. And we want to select 26 gauge TSP.

Now to set its properties same thing we're going to click on library and go to library here click general we want to select a bare wire and we want to select the 26 gauge wire.

Other things we want to do here is the termination, so we need to be here 50 ohm, but here we want it to be 0 ohm, so by default both will be 0 ohm, so to make that adjustment we click on termination and click here on terminations and now we see the two points here once I click on it you see it get highlighted with pink so this is this one we need it to be 50 ohm and this one stay as zero then we click x and we click on the green check mark so now we define the first conductor.

Click on the termination button and select the point Click here, so now there's nothing going to that side and this would be my termination And similarly, we want to select the other end which should already be selected Now we can verify by clicking here on terminations So this one is 50 as you see and the other termination is 0 Now we click the green check mark.

So now we have the cable fully defined and to do some verification here we can go to the mHarness tab and go to cabling and click this button to inspect the cross section. So if we put the marker here at this cable so you see now how it is defined the cable outside the enclosure.

Now we want to define the excitation, and we want the excitation to be defined here on these wires. So let's rotate this model. We want to define it on these wires which basically connects to these pads. So how do we want to define it?

We want to define this wire to be PEC, this wire to be PEC, and here's the current source.

To do that the easiest way is that we select this wire and we right click and we say assign line material to be PEC Similarly we can select this wire and right click and assign line material and select PEC Or we can do this from here by expanding the free lines and select which one of those and write and define the material Now we want to define the current source here To do that we can go to the EMA3D tab and select, go to Excitation and select Current Source here.

And we need to select the geometry for the current source. We're going to go to the Line Selection mode and we want to select that section.

And here you can select whether you want current type electrical magnetic or the x direction which the the the current direction so I want to keep it here to be the x and we're going to now next click on the green check mark.

Okay and as you see the direction is going from the and that's how we want it. Okay, so now after we define the current source, we need to define the signal on that current source. To do that, we go to the same thing, EMA3D tab, and we want to select a rectangular signal.

and here we can do modification to that and define the signal that we want but here let's define a 0.752 T cycle a frequency of 20 megahertz to 20 E6 and the rise and fall time to 10 nanoseconds so it will be 10 E-8 10ns E-9, and here similarly 10 E-9, furtherize on full time.

We can give it a different name or we can keep it and we just click X. So now if we scroll down, we see that the signal got defined here. Now we need to attach that signal to the current source we want. So to do that, we click on the signal and drag it and drop it on top of the current source.

And now they got attached to each other. Okay, now we want to define the solution domain. To do that, we click on Domain here. and we can change it manually or define it here. First, we want to change the time.

Let's set the stability margin to 20% and we want to change this to 1E- 7. And let's now minimize that and want to change now the lattice, the minimum, maximum, and step size.

The first thing we want to adjust is the step size, so let's change that to be 1.5875 and let's copy that number and paste it here, paste it here as well.

And now we want to change the minimum to be minus 180.975, minimum Y to be minus 147.635, minimum Z to be minus 12.7, maximum to be 196. 85. Now we define the solution domain which encloses the entire geometry.

As you remember, the domain has a step size of 1. 587. We need a smaller step size for the area or volume that encloses the PCB. To do that, we can add another domain that encloses the PCB. That is possible here by going to the EMA3D tab and selecting the variable grid.

Similarly, we can place it wherever we want manually or we can define it here. We want to find the step size here to be 0.24 to be much smaller than the the the step size for the larger domain that encloses everything.

So we want to make the x step size to be 0.24 and 0.24 for the y and 0.36 for the z to have a finer mesh meshing to for the PCB.

and we also want to change the location of it so the minimum to be minus 83.04 minus 36.48 5.04 and for the maximum x minus 21.12 Now we see if we zoom in here that there's another domain defined for the variable grid1 defined around the PCB.

Now since we have two different domains with two different step sizes this can create an issue for The reason for that is for this domain the smaller step size will need to be gradually changing as you exit from this domain to the larger domain.

So the step size around the mHarness will not be uniform and that can create an issue with M harness solution To do that we want to define another variable grid to ensure that we have a constant step size along the route of the M harness To do that, same thing, we define another variable grid mesh.

and we want to give these dimensions so let's change the step size to be 0.5, 0.5, and 0.5 and for the minimum to enclose the M harness would be 24, 69, 32 and the maximum is 54. 5. Define a point field probe Define a 3D probe Similarly, we can manually place it and define its size, or we can do it from here.

So let's go expand bonds, minimum and maximum, and we want to define this to be 22.225 and minus 117.475, We don't want it to be matching the domain.

So we want to change that to be 4E-10 seconds and end 1E-8 and for the step we want to change this to false and define it manually to be 2E- 10. and then we click on the green checkmark. And so this is the 3D prop that is defined. Next, let's just confirm the simulation settings.

So we can go click here on settings. If you have GPU, make sure that this is checked and significant figures displayed. Yeah, let's make this seven and that's it. Click apply settings. Now we can start meshing and simulating the model. To do that we click here on Mesh to mesh the model.

So now the mesh is created and we can zoom in and rotate the model to inspect it. After the mesh is created, we can click on start to start the simulation. It will do a first validation check. And now we can click run.

And this simulation will take a while depending on the computer resources that you have.

So now after the simulation is done we can look at the results so we can go to the field prop we defined and compute the field statistics and we point to the current source that we used and click OK and the field statistics get calculated and now we see under visualization there is also we can right click on field statistics now and click on show and this is the field statistic data we can right click and configure this plot and chart can change that from for example to DB and you can make different changes.

We can also plot the fields along the bulk data probe, which is the 3D probe that we defined. So we can do that by right-click on the bulk data probe and click select visualize 3D. And now because we defined many time steps, we can select which time step we want to plot the fields at.

So for example, let's select this point and click on visualize results. You can select the time steps, say 10, and then you can click here to select which one you want. And that's all for this demo, and thank you for watching. Please contact us at https://ozeninc.com/contact for more information.