input impedance of a passive mixer

[uzay1983]

input impedance of mixer

Hi Guys,

I am trying to model the input impedance of a passive mixer. input impedance of mixer is time varying impedance therefore, correct analysis should be done in time domain to measure it. AC analysis is a way but it will not yield a correct model for it.

What I am doing is, I am applying LO and applying a small amplitude sin wave.

However I can not find a way to get impedance! If someone do it so, can you help me?

 

[pancho_hideboo]

Re: input impedance of mixer

You can evaluate impedance averaged over one period of Local signal by invoking master steady state analysis using one tone large signal followed by slave small signal analysis.

See http://www.designers-guide.org/Forum/YaBB.pl?num=1240334878

If you use Agilent ADSsim(RFDE), use 1tone-HB-SS Analysis.
See "Setting Up Small-Signal Simulations" of http://edocs.soco.agilent.com/display/ads2009/Harmonic+Balance+Basics

See parameter of "P_USB" in http://edocs.soco.agilent.com/display/ads2009/P+1Tone+(Power+Source,+Single+Frequency)

Also see the followings.
http://edocs.soco.agilent.com/display/ads2009/Large+Signal+Amplifier+Simulations
http://edocs.soco.agilent.com/display/ads2009/Simulation+of+a+Differential-Mode+Mixer

If you use Agilent GoldenGate, use 1tone-SSNA Analysis.

If you use Mentor EldoRF, use ".SST" as Master Large Signal Steady State Analysis and ".SSTAC" as Slave Steady-State AC Analysis.

If you use Synopsis HSPICE RF, use "Multitone Harmonic Balance AC Analysis (.HBAC)".
**broken link removed**

If you use Cadence Spectre, use PSS/PAC Analysis.

 

[BigBoss]

input impedance of mixer

Mixers are nonlinear blocks and that's why small signal analysis are not valid including AC and s-parametrs..
Instead, a HB analysis by putting current meter can give you the input impedance of a mixer.
Or transisent simulation will also give but I prefer to use HB..

 

[uzay1983]

Re: input impedance of mixer

I am using cadence rf-spectre. Thank you so much for your answers

 

[pancho_hideboo]

Re: input impedance of mixer

Small signal analysis as slave analysis for master large signal steady state analysis is different from conventional small signal analysis.

If you use Cadence Spectre, former is PSS/PAC and latter is AC.

 

[uzay1983]

Re: input impedance of mixer

I have one additional question about PSS+PAC simulation combination? What is the difference between AC and PSS+PAC?

PSS is a large signal but if the circuit will be linearized again in PAC, why shouldnt I use only AC instead of PSS+PAC.

Could you explain it briefly. Thanks.

 

[pancho_hideboo]

Re: input impedance of mixer

PSS is a large signal but if the circuit will be linearized again in PAC,
why shouldnt I use only AC instead of PSS+PAC.

AC analysis is a small signal analysis around static operation points determined by DC analysis.

PAC analysis is a small signal analysis around dynamic operation points determined by PSS analysis.

AC, XF, SP, Noise and STB are slave analyses for master DC analysis.
These are analyses for LTI(Linear Time Invariant) System.

PAC, PXF, PSP, PNoise and PSTB are slave analyses for master PSS analysis.
These are analyses for LTPV(Linear Time Periodic Varying) System.

QPAC, QPXF, QPSP and QPnoise are slave analyses for master QPSS analysis.
These are analyses for LTQPV(Linear Time Quasi Periodic Varying) System.

 

[uzay1983]

thanks so much pancho

 

[mbyoussef]

Re: input impedance of mixer

Mixers are nonlinear blocks and that's why small signal analysis are not valid including AC and s-parametrs..
Instead, a HB analysis by putting current meter can give you the input impedance of a mixer.
Or transisent simulation will also give but I prefer to use HB..

Mixers are linear time variant networks. AC analysis is valid once a steady-state operating point is found => PSS/PAC is valid for mixer simulation

 

[steven_l]

Re: input impedance of mixer

Hi Guys,

I am trying to model the input impedance of a passive mixer. input impedance of mixer is time varying impedance therefore, correct analysis should be done in time domain to measure it. AC analysis is a way but it will not yield a correct model for it.

What I am doing is, I am applying LO and applying a small amplitude sin wave.

However I can not find a way to get impedance! If someone do it so, can you help me?

Hi friend, i am designing passive mixer too.
but lots of problems come up such as

Maybe you never have this problem. But i really want to know smoe methods of design and stimulation.

Can you help me?

 

[Milad-D]

I am trying to model the input impedance of a passive mixer

FYI:It is already very good Modeled in the recent literature.

 

[BigBoss]

Re: input impedance of mixer

Mixers are linear time variant networks.

If it was so, we don't see any harmonics at its output.

 

[Milad-D]

Re: input impedance of mixer

If it was so, we don't see any harmonics at its output.

You should know that : two types of circuits produce harmonics: 1.nonlinear circuits and 2. linear time variant circuits.

Interestingly, people always had discussion about Mixer: Should we call it nonlinear or linear time variant system. Depending on how you look at the mixer, you can call it nonlinear or linear time variant system.
I recommend you to read the first pages of RF Microelectronics by BEHZAD RAZAVI to clarify this.