Urgent:test fixture design and in-fixture calibation methods

[Ivan_]

Hi guys,
I havt to get the small-signal and the large signal equivalent models of an HEMT with some measurement-based techniques. In order to do that, I need to design a proper test fixture to avoid poor grounding and potential oscillations, for both S-parameters measurements and DC-measurements. I know I have to use bias tees, but despite I did it, some instability took place in DC measurements, resulting in strange I-V curves. I ask: does anybody know any good ustrip geometrical configuration for these measurements? I would really appreciate layout schemes and dimension constrains and rules.
Another important point is the in-fixture post calibration for S params meas. I know the typical TRL method can be used, but I think symmetry of the test fixture can be considered to simplify the procedure. Can anybody plz provide me of info about methods for symmetrical test fixtures and even some matlab code implementing the procedure/s?

Many thanks in advance.

Ivan.

 

[Ivan_]

Re: Urgent:test fixture design and in-fixture calibation met

Is there anybody dealing with microwave active device small-signal and DC measurements? I would really appreciate advice about this topic.
Thanks :wink:

I.

 

[ge]

Re: Urgent:test fixture design and in-fixture calibation met

Ivan,

What frequencies are you working at? Is this a FET or MMIC? If doing a large signal model, I assume you are building a power amplifier.

 

[Ivan_]

Re: Urgent:test fixture design and in-fixture calibation met

Hi ge,
it's a low noise packaged HEMT. I have to get DC I-V curves at first to get the large-signal model. This can be useful for understanding what's the best quiescent point to let the amplifier to be working at.
As for S-params, I'm thinking to use the amplifier at 10GHz, but I need a characterization from DC to 18GHz at least. Any directions about test fixture and test fixture calibration?
have a look at my topic:
and tell me what do u think about.

Bye

 

[hcseu]

Hi Ivan
There are many good application notes about de-embedding and in fixture measurement at agilent
the paper listed below may help you:
1.Network Analysis - De-embedding and Embedding S-Parameter Networks (1364-1)
2.Accurate Measurement of Packaged RF Devices
3.Network Analysis - In-Fixture Measurements (1287-9)
4.Designing and Calibrating RF Fixtures for Surface-Mount Devices
5.Calibrating Standards for In-Fixture Device Characterization
......
Enjoy

 

[Ivan_]

Re: Urgent:test fixture design and in-fixture calibation met

Thanks a lot hcseu, I think they can be very helpful to me.