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tjaf

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Noise analysis on windowed correlator
Feb 07^th, 2007, 8:40am

Hi all,

Let me first briefly try to describe the circuit I am trying to simulate.

The mixer is a downconverting mixer which has a windowing function (controlled with W). The output of the mixer is a current which gets integrated on the capacitor. When the window is closed (W=0), the value is retained. Right before the window is opened again, the capacitor is reset. The figure below shows an example transient simulation when RF and LO are two in-phase sinewaves.

I am trying to do a noise analysis on this thing. Any pointers as to which simulation/testbench I should use (SpectreRF)? I don't think PSS/PNOISE will work in this case?

Thanks in advance,
Nick

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ACWWong

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Re: Noise analysis on windowed correlator
Reply #1 - Feb 7^th, 2007, 10:37am

I think pss/pnoise should be ok, depending on what you want to measure.
From looking at your transient, a periodic steady state at the output is visable (30ns period), so if freq of rf and lo are also harminically related then pss should converge and pnoise will give you the noise over the cycle (in your case with time average with W=1 for 1/5 of the cycle and W=0 for the other 4/5 of the cycle).
You could of course try independent simulations with W=0 or W=1 to see the noise in each state ?

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Ken Kundert Global Moderator Offline Posts: 2386 Silicon Valley	Re: Noise analysis on windowed correlator Reply #2 - Feb 8^th, 2007, 12:00am You would need to use PSS & PNoise as the circuit clearly has a periodically varying operating point. However, that is as much as can be said until you tell us about the next stage. Presumably it is a sampling stage, which would imply to need a strobed noise analysis. -Ken
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tjaf

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Re: Noise analysis on windowed correlator
Reply #3 - Feb 8^th, 2007, 12:45am

Thanks for the reply's. I will try the PSS/PNOISE. I assume that for the PSS, I should set both the RF (small signal) and LO (large signal) port to dc sources, so that the only periodic input signal is W?

The next stage is indeed a sampling stage (not designed yet), somewhere after the window closes and before the capacitor is reset. I didn't know about the strobed noise analysis. I'll look it up.

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ACWWong

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Re: Noise analysis on windowed correlator
Reply #4 - Feb 8^th, 2007, 3:37am

tjaf wrote on Feb 8^th, 2007, 12:45am:

Thanks for the reply's. I will try the PSS/PNOISE. I assume that for the PSS, I should set both the RF (small signal) and LO (large signal) port to dc sources, so that the only periodic input signal is W?

no i think you'll need a large signal LO to capture the frequency translating effects of the mixer. RF as a dc source is ok. It'll still be a fairly quick simulation if you make LO freq and W freq harmonically related....

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