[SI-LIST] Re: de-embedding of mems
- From: "Swanson, Dan" <Dan.Swanson@xxxxxxxxxx>
- To: "'kbhate@xxxxxxxxxxx'" <kbhate@xxxxxxxxxxx>,si-list@xxxxxxxxxxxxx
- Date: Tue, 23 Sep 2003 08:57:37 -0400
Kaustubh,
True de-embedding is more complicated than what
you are describing. To accurately de-embed a
DUT from its fixture you compute the S-paramters
of each half of the fixture from the connector
to the plane of the DUT.
To get the S-parameters of the fixture, you basically
have to do a second set of "calibration" measurements
on each half of the fixture. The math and the techniques
are exactly the same as those used to calibrate your
vector network analyzer. So you might use several known
loads (short, open, load) or you might use several
known lengths of transmission line (TRL).
Once you get the parameters of the fixture, you can
mathematically remove the fixture from the global
measurement of the fixture plus DUT.
An alternative would be to calibrate the ANA and fixture
all in one go. All your cal standards are at the DUT plane.
Have to know how to modify the standard cal procedure or
cal coefficients.
>
> De-embedding for mems passive componenst would be different
> than for the active
> devices like transistors where the de-embedded parameters are
> not referenced to,
> any "entity".
>
I don't understand this statement. True de-embedding described
above is the same for active and passive devices.
Agilent used to have some App notes on the math of ANA calibration.
What they call an "error model" can be interpreted as the parameters
of your fixture. There is also a lot in the RF/microwave literature
on various schemes for de-embedding.
Dan
> -----Original Message-----
> From: Kaustubh Bhate [mailto:kbhate@xxxxxxxxxxx]
> Sent: Tuesday, September 23, 2003 7:57 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] de-embedding of mems
>
>
> Hi,
> Can somebody point me to a standard/known procedure for doing
> de-embedding of
> mems measurements?
>
> I have seen a paper that subtracts the insertion loss (in
> dB)of an identical
> thru-line from "a mems-switch-interconnect" assembly
> measurement(in dB).Is that
> a correct/reasonable approach of eliminating the loss from
> the pad parasitics
> and the interconnects?
> If the the raw s-parameters are subtracted for the same, as
> above,(instead of at
> the dB level) the results are totally different.
>
> Also what about de-embedding for return loss? Using the same
> approach as above
> (working in the dB domain), the results do not make sense.
>
> De-embedding for mems passive componenst would be different
> than for the active
> devices like transistors where the de-embedded parameters are
> not referenced to,
> any "entity".
>
> Thanks in advance.
>
>
> Regards,
>
>
> Kaustubh Bhate
> Transducers Group
> NMRC
> LEE Maltings
> Prospect Row
> Cork.
> Ph:353 21 4904401
>
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