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Design >> RF Design >> Impedance probe in SpectreRF
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Message started by Dan on Nov 16^th, 2005, 2:30pm

Title: Impedance probe in SpectreRF
Post by Dan on Nov 16^th, 2005, 2:30pm

Hello

I am working on a multi-stage PA in SpectreRF and have run across difficulties in designing the interstage match networks. Would anyone know of a method of measuring impedance without breaking the circuit? I can use the RF ports in the s-parameter simulation to measure input and output impedance of the amplifier. But I can see no option to measure the Z load of the interstage match network, for example. This can be estimated by breaking the circuit and wiring an RF port to this point, but the parasitics will change. Is there a method for designing a non-invasive reflection coefficient probe, and having this measurement roll into the s-parameter menu?

Thank you for your time,
Dan

Title: Re: Impedance probe in SpectreRF
Post by Jess Chen on Nov 16^th, 2005, 2:45pm

As I understand your problem, you want to measure the impedance looking into a load while it is being driving by another circuit. If that is true, you should be able to drive the node between the source and load with a current source and place current probes on either side of the injection point. You can then compute zload, as well as zsource, by taking the ratio of the voltage at that node to the appropriate current. You can then convert the impedances to reflection coefficients. You should be able to write some waveform calculator functions to streamline the computations.

Title: Re: Impedance probe in SpectreRF
Post by Dan on Nov 18^th, 2005, 7:15am

Thank you for your input Jess. I'll give this a try for a few frequency points.

Dan