Ken Kundert
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Alice, What type of circuit follows your switched-capacitor filter? Is it a sampled-data circuit, such as a sample and hold or ADC, or is it a continuous-time circuit, such as a continuous-time anti-alias filter? A sampled-data circuit is only sensitive to the noise your SC filter produces at the instant when it samples, while a continous-time circuit is sensitive to noise produced at all time during the clock cycle.
If your SC filter is followed by a continuous-time circuit, then you are interested in the continuous-time behavior. SpectreRF computes this directly. If your SC filter is followed by a sampled-data circuit, then you are interested in the discrete-time behavior of your circuit. In this case, you must either use SpectreRF's strobed-noise feature or add an ideal sample-and-hold to the output of you circuit so that only the noise at the sample point is measured.
-Ken
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