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Transient Noise Simulation in Cadence Virtuoso

Maria98

Hi 

I am using Cadence Virtuoso IC6.1.8-64b.83.

For a demodulator with 140GHz carrier and 40Gbps data rate, i set the transient noise with only the demodulator noise contribution ON. When i simulate it with Fmax = 700GHz, it gives higher amplitude of demodulated output signal (34mv) where as when simulated with FMax = 280GHz it gives low amplitude of the detected output signal (24 mv). I did not set Fmin so put it as default 1Hz. What is the appropriate setting in this case? Thank you

Parents

  • Hi Maria,

    So, noisefmax is limiting the maximum time step of the transient analysis. Since this is changing the amplitude of your output, I would question the accuracy of that simulation. I think you should go step-by-step. Turn off the noise and try to get the robust simulation results first by tightening the accuracy options. Are you running a conservative mode (or cx mode with Spectre X)?

    Once you get robust simulation results you can turn of the noise and start thinking about noisefmax. Its value is sometimes tricky to obtain. A good practice is to sweep it from some reasonable value like 3x(carrier freq) up and see if yuor noise measurements converge to some accurate value. Then you should choose the lowest noisefmax that gives relatively accurate results, so you do not sacrifice your performance (simulation speed) all that much.

    BR

    /Janko   

  • in reply to JankoK

    In addition to Janko's excellent advice, I wonder whether you might be able to use the SpectreRF analyses (either hb/hbnoise or pss/pnoise) - this might be a more efficient way of getting accurate results (it depends somewhat on whether the circuit is periodic and has a periodic response). Usually transient noise is best kept for the scenarios where there is not a better way of doing it - because it is inherently difficult to simulate small noise signals over a long time at high frequency (with lots of points). 

    Andrew

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  • in reply to JankoK

    In addition to Janko's excellent advice, I wonder whether you might be able to use the SpectreRF analyses (either hb/hbnoise or pss/pnoise) - this might be a more efficient way of getting accurate results (it depends somewhat on whether the circuit is periodic and has a periodic response). Usually transient noise is best kept for the scenarios where there is not a better way of doing it - because it is inherently difficult to simulate small noise signals over a long time at high frequency (with lots of points). 

    Andrew

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