Substrate definition in ADS2006A Momentum?

My project is to design a single turn rectangular loop antenna on GaAs (100μm) substrate. I am trying to simulate a loop on GaAs subtrate only; without any background metalization/ground. But my problem is: I cann′t define the subtrate without ground/metalization. Whenever I want to defíne air-metal-GaAs-Air, it automatically brings another metal layer in between the GaAs and bottom Air layers. Though this unexpected metal layer is not mapped, I am not sure whether it affects my results or not! I am attaching the substrate definition window.

Can anyone tell me the exact way of defining such kind of substrate?

Thanks in advance

Sifat

Adding an thick air layer between GaAs and Gnd

Hi dingjingfeng,

Thanx, but again the problem is.. one UNMAPPED (---- dotted) metal layer! (Substrate1.jpg).

In my opnion, if you don't draw any thing with this
then it's OK

nuddin:

I think you can get a free space boundary at the bottom by selecting the layer indicated ///////GND//////// in the substrate edit window.

Then, an option will appear called "boundary". Change it from "closed" to "open."

I think this will put an open boundary under your GaAs substrate. However, I think it might be a good idea to put a large air layer underneath this. I don't know how Momentum handles a free space boundary that is up against a dielectric.

--Max

Thank you Max.

Ya, but it returns me an infinite thickness of GaAs instead of infinite freespace! I cannt control the substrate thickness.

..nuddin

nuddin:

Yes, it does. But you can then click the "add" button to put another dielectric under the GaAs layer. It will come up by default with the same properties as GaAs, but you can change the properties of this layer to match that of air or vacuum.

I haven't performed any simulations with this setup, so I can't tell you whether or not Momentum will handle this correctly.

Good luck,

--Max

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