[SI-LIST] Re: Coax vs. Microstrip
- From: "Scott McMorrow" <scott@xxxxxxxxxxxxx>
- To: cacofonix98@xxxxxxxxx
- Date: Tue, 25 Mar 2003 14:31:28 -0800
Siva,
It depends upon the type of SMA launch that you are trying to model,
edge mount or top mount. But, in either case, it would be best, in your
"popular tool" to model the SMA interface to the PCB out to the point
that it becomes coaxial, and the microstrip structure to where it truly
is a microstrip. At that point, you can apply waveports that are
matched to the characteristic impedance of the structures. You should
adjust your geometries and material properties so that the waveports
achieve a 50 ohm match before you simulate the rest of the structure, as
your return loss will be incorrect if there is mismatch at the waveport
boundaries.
Once optimized, then you can vary the impedance (geometry) of the
microstrip trace to determine the full operational range of return loss.
regards,
scott
SS wrote:
>Hello,
>
>I am trying to model the SMA to PCB launch interface
>in a "popular tool".
>I am making a couple of simplifications
>1) modeling only the part of the SMA that is embedded
>in the PCB.
>2) Launch into the center conductor through a 50 ohm
>microstrip structure.
>
>Are these simplifications realistic or valid? If not,
>how far off from reality is it compared to a coaxial
>launch?
>
>Thanks
>Siva
>
>
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--
Scott McMorrow
Teraspeed Consulting Group LLC
2926 SE Yamhill St.
Portland, OR 97214
(503) 239-5536
http://www.teraspeed.com
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