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Designing an aperture coupled antenna in ADS

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butlermatrix

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Hello,

I am trying to design an aperture coupled antenna in ADS but this version 2016.01 doesnot have any EMDS option which I can use to model the thickness, dimensions, loss tangent, dielectric constant for the layers!
Also when I am clicking EM and proceeding to "substrate" under EM I cannot get the design I would want to have i.e. a top patch(conductor) followed by dielectric then comes a ground plane with a slot followed by a dielectric again and at last the feed network.
Can anyone please suggest me how I can realise such a structure in ADS ?
If anyone has any tutorial videos or model documents which can aid me in realising this design would be of great help.
Any sort of help will be appreciated.

Thank you in Advance.
 

butlermatrix said:
I am trying to design an aperture coupled antenna in ADS but this version 2016.01 doesnot have any EMDS option which I can use to model the thickness, dimensions, loss tangent, dielectric constant for the layers!
Click to expand...

Do you have the required license for this feature? ADS has two EM solvers: Momentum and FEM (formerly EMDS).

If you don't have the FEM license, you should get reasonable results with Momentum also. The difference for your antenna case is that Momentum uses infinite substrate size. Not exact for your case, but maybe good enough.

butlermatrix said:
Also when I am clicking EM and proceeding to "substrate" under EM I cannot get the design I would want to have i.e. a top patch(conductor) followed by dielectric then comes a ground plane with a slot followed by a dielectric again and at last the feed network.
Can anyone please suggest me how I can realise such a structure in ADS ?
Click to expand...

What exactly is your problem, how far could you get? You just need to add dielectric layers, and place metals between them. I would suggest to model the slot as a conductor layer also, and simply draw the metal around the slot. The substrate editor "slot layer" option has some limitations for loss modelling, I would not use that.



Momentum tutorial:
https://www.youtube.com/watch?v=QYMPV1qn1oc
 
Hi,

Thank you so much.
Yeah I have both Momentum and FEM.
I understood the solution to my problem. I need to change the template i am using it was the Alumina 25um to two layer FR4. But I am finding it hard to realize what I actually need to design in the layout window?
i.e I need to draw the patch and the slot and the feed line network and mark the ports accordingly?
 

butlermatrix said:
I need to change the template i am using it was the Alumina 25um to two layer FR4.
Click to expand...

The template is only a possible starting point. You need to change the stackup as required for your PCB, so it can be very different from the templates. Check the right mouse button options!

butlermatrix said:
But I am finding it hard to realize what I actually need to design in the layout window?
i.e I need to draw the patch and the slot and the feed line network and mark the ports accordingly?
Click to expand...

For Momentum, you need to draw all metal items and place ports.

For FEM, you need to draw all metal items, the substrate itself and place ports. I use air background material and place substrate as a dielectric via, but it is also possible to define the substrate layers as dielectric + bounding area layer, see online help.

And check materials in 3D view before simulation, especially if you are new to the ADS substrate editor.

 
Hi,

For FEM Simulation do you draw ground layer and substrate too?
I was drawing just the slot and stacking one after the other. Is it necessary for me to draw the ground layer and then make the slot on it?
Thanks
 

butlermatrix said:
For FEM Simulation do you draw ground layer and substrate too?
I was drawing just the slot and stacking one after the other. Is it necessary for me to draw the ground layer and then make the slot on it?
Click to expand...

It is easy to misunderstand the details here:

As I described above, in Momentum there is an alternative method (draw slot = anti-metal = negative) that can be used if the conductor layer is mapped as a "slot plane". However, this is more limited in solver accuracy, so I would NOT usethis. As I described above, I recommend to draw the normal metal "strip plane" and just leave a slot in that metal.

In FEM, you always draw the metal, similar to the Momentum strip plane. So yes, you draw all metal that exists in the PCB. And as I described above, for Momentum you also draw the dielectric, as shown in my screenshot.

If your question refers to creating the slot in the editor: you can draw metal and slot on the same layer, and then use Edit > Merge > Union Minus Intersection

merge.PNGmerge2.PNG
 

Can it be done instead of placing the "diel" as in the screenshot you provided me with (attached below)?
5583224800_1500103145.png
 

butlermatrix said:
Can it be done instead of placing the "diel" as in the screenshot you provided me with (attached below)?
View attachment 140005
Click to expand...

I don't understand your question. For FEM simulation you need to draw metal conductors and the PCB dielectric. In my screenshot that you show, "diel" is the dielectric, so you need to draw a rectangle on the "diel" layer for the PCB dielectric. And of course, you also need to draw patch and ground on the metal layers.

Why don't you try, check in 3D preview if all materials are there, and upload your ADS project if there are problems?

- - - Updated - - -

I decided to create an example project for you, quick & dirty based on dimensions from a published paper.
Setup is for FEM solver, ADS version 2014.
Hope this helps and answers the questions now. If something looks wrong, it might be my mistake because I was too fast in putting the example together late in the evening ....
View attachment aperture_coupled_patch_wrk.zip
 

I am using Momentum Microwave instead of FEM and modeling the ground layer as "slot layer" in substrate editor. I cannot use FEM as there is some problem with EMPro in my machine.
If I model according to your design I would need to model the slot dimensions and position of the slot every time on the metal layer I am drawing as my ground plane to obtain desired results. I am attaching a screenshot of what I am actually doing.
ADS.png


As for the substrate editor I am using the following
ADS2.png


Do you think its the right way to approach the design? I will use FEM when I get access to EMPro. Right now I am looking for some reasonable results which will give me some idea as a base to work on.
 

butlermatrix said:
and modeling the ground layer as "slot layer" in substrate editor.
Click to expand...

*updated*

I tried, and got it to work. For Momentum, "slot layers" are infinite grounds, so you just place the (+) pin for the port. Momentum will find & use the nearest infinite ground (here: slot plane).

Here is my example with all 3 options: FEM, Momentum strip, Momentum slot:
View attachment aperture_coupled_patch_wrk.zip

If you want to tweak geometries, you can add EM parameters, as I described in this appnote, chapter "EM parameters for “drawn layout” from polygons"
https://muehlhaus.com/support/ads-application-notes/em-parameters-momentum
 
Last edited:

Hi, I ditched the idea of modelling just the slot instead of an entire metal strip with a slot in it. I am moving forward with the idea you recommended previously by designing a metal strip as my ground plane and making a slot in it. I have drawn the dielectrics in my layout as well
Do I need to connect my ground plane to a port too? In the design screenshots I posted the "pc1" layer in my screenshot is the feedline and I am connecting it to a port. Do I need to connect my ground to a port as well?
I will post a screenshot of the current one I am designing.
And I am using a linux machine at my univ it doesnot allow me to run any projects after downloading due to security reasons. Can you please send me a few screenshots of the design you made?
 

butlermatrix said:
Hi, I ditched the idea of modelling just the slot instead of an entire metal strip with a slot in it. I am moving forward with the idea you recommended previously by designing a metal strip as my ground plane and making a slot in it.
Click to expand...

ok.

butlermatrix said:
I have drawn the dielectrics in my layout as well
Click to expand...

I was assuming that you use FEM solver. For Momentum, the dielectric is defined in the substrate, with infinite size. The "dielectric via" is not used in this case, that is only for FEM.

butlermatrix said:
Do I need to connect my ground plane to a port too? In the design screenshots I posted the "pc1" layer in my screenshot is the feedline and I am connecting it to a port. Do I need to connect my ground to a port as well?
Click to expand...

Yes, for finite (drawn) grounds you must place a pin on the ground plane, and assign it as the (-) terminal for the port. Please check my example project above!

butlermatrix said:
And I am using a linux machine at my univ it doesnot allow me to run any projects after downloading due to security reasons. Can you please send me a few screenshots of the design you made?
Click to expand...

That is really time consuming to make all screenshots, and document things. And we have seen above that it's easy to misunderstand things. You should find a way to download my *.zip, which contains the packed ADS project.
 
Hi,

Any idea on why I am receiving these warning when I have placed the ports near to each other.

Thanks in advance

ads_error.jpg
 

any idea on the rate of error when I am using Momentum solver instead of EMPro or HFSS 3D Solver for antenna design? Will I see drastic changes in result when I use a 3D solver?
 

butlermatrix said:
any idea on the rate of error when I am using Momentum solver instead of EMPro or HFSS 3D Solver for antenna design? Will I see drastic changes in result when I use a 3D solver?
Click to expand...

There are some antennas like Vivaldi that radiate mostly in the substrate plane, these will not work in Momentum because Momentum use an infinite substrate size for calculation. Other antennas like patch or PIFA work fine in Momentum, with only small differences in S-parameters from finite vs. infinite substrate. You need to ignore the "dip" in Momentum antenna pattern at the horizon that is caused by an infinite substrate, this is not real.

Having both and having checked results for both solvers, I use Momentum most of the time for antenna simulations. I use FEM to double check in cases where there are other 3D objects near the antenna, or for antennas that radiate mostly in the x-y (substrate) plane as mentioned above.
 
Suppose I want to design a reflector at the back of my antenna design so that the amount of back radiation is cancelled. In ADS how do I simulate it? using a cover plane in the substrate menu or do I have to draw a metal plate and mark it as strip plane in the substrate tab of ADS Layout?
 

butlermatrix said:
Suppose I want to design a reflector at the back of my antenna design so that the amount of back radiation is cancelled. In ADS how do I simulate it? using a cover plane in the substrate menu or do I have to draw a metal plate and mark it as strip plane in the substrate tab of ADS Layout?
Click to expand...

I would use the infinite ground plane (bottom cover).
 

When I use a reflector, does it reduce the antenna radiation efficiency?
 

Is this an antenna design question, or do you get unexpected results from simulation?
 

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