aaron_do wrote on Apr 23rd, 2009, 7:29pm:for cadence spectre, the way I normally check the input impedance of a passive mixer would be to run PSS/PSP analysis.
You can then plot the Z parameters or the Y parameters of the input port.
If you use PSP or QPSP of Cadence Spectre, you have to use "analogLib/port" which results in load at observation nodes.
Such loads at observation nodes are not preferable especially for interstage impedances measurements.
Here even if you increase port resistance, it can not be a solution.
I use my own impedance probe. For example, the following is single-ended impedance probe.
http://www.designers-guide.org/Forum/YaBB.pl?num=1221012939In Agilent ADSsim, such impedance probe(Short_Probe or SP_Probe) is provided as standard probe.
http://edocs.soco.agilent.com/display/ads2009/SP+Probe+%28S-Parameter+Probe%29But I can't use this ADSsim's probe in Cadence Spectre.
And this probe is restricted to only conventional SP-Analysis.
Instead I created my own impedance probe by using vsources, isources and ideal-transformer.
This impedance probe is valid not only for Agilent RFDE(ADSsim) but also for Cadence Spectre.
And this impedance probe is valid not only for conventional Small Signal AC Analysis but also for Small Signal AC Analysis subjected to Master Large Signal Analysis such as HB-SS of Agilent RFDE(ADSsim) and PSS/PAC of Cadence Spectre.
Assume cascaded connections of LNA, Mixer, Filter and IF_Amp, etc.
How do you measure any interstage impedances which see left and right ?
I can measure any interstage impedances using my own differential impedance probe.
Here I can evaluate Zleft_diff, Zleft_comm, Zright_diff and Zright_comm of any interstage at same time.
Ken Kundert wrote on Apr 23rd, 2009, 11:47pm:You know, SpectreRF does not require the use of ports as sources. You can use either voltage sources or current sources too.
We all know
any vendor's RF simulator except for very old one such as "SuperCOMPACT" does not require the use of ports as sources.