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SpectreRF to Simulink (S parameters)? (Read 1753 times)
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SpectreRF to Simulink (S parameters)?
Jun 07th, 2016, 1:15am
 
Hello,

I've the following intricate problem: I have a transistor-level design of an RC integrator (OTA in feedback) and I want to test what errors are introduced due to nonlinearity. Problems:
  • Classical methods relying on harmonic signals do not apply because I am interested in actual (random) signals
  • I could make sure that HD3 is extremely low within the integration bandwidth. But it turns out the tradeoffs are tight and I want the swing to be as large as possible for a certain effective integration error (mean squared error)
  • Small-signal nonlinearity is frequency dependent because the loop gain (which improves the linearity) of an integrator is a bandpass
  • The limiting factor is large-signal nonlinearity due to saturation (when the output signal comes close to the rail)
  • Even if I would use Spectre itself and run a transient simulation with a random input signal ... to what would I compare the output? I cannot create a transistor-level model with everything but nonlinearity ...


My idea would be: Characterize the circuit with SpectreRF: Sweep all input frequencies, sweep input power and get output power (amplitude and phase). There would be a 2D array which would give me the complex gain for a particular input power and frequency.

A Simulink block (to be found) would interpolate between them.

Then for another Simulink block I just keep the smallest two power variables in the model and use linear interpolation: This should then constitute a perfectly linear but frequency dependent model.

Now sending the same data through the 2 Simulink blocks should give me the difference that is only caused by the nonlinearity and I can directly obtain an NMSE value.

Can I use SpectreRF to export frequency dependent nonlinearity behavior? Are S-parameters what I am looking for? How to?

Any ideas for the Simulink part?

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