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Summary

This PR simplifies complicated oscillation signal initial guess, in which we usually must take special care for low frequency signal (e.g. FFT is not robust to bias, thus we should precisely eliminate base offset, but this is hardly estimated for low frequency signal). This PR adds/modifies several initial guess functions, and these functions are integrated into a meta function composite_sinusoidal_estimate that internally assembles the best algorithm.

Details and comments

New algorithm sinusoidal_freq_offset is also introduced by the PR. This function simultaneously estimates base offset and frequency and thus this is robust when both base and frequency are not known. This gist shows some robustness analysis I did, and the result indicates the algorithm provides reasonable guess when data contains >T/2 samples.

(something still missing)

  • Any good algorithm to estimate phase? I also tried correlation (convolution) technique but it doesn't work well for noisy data.
  • Slight degradation of guess quality of exp_decay when it is used for damped oscillation signal. Any thoughts for improvement?

@nkanazawa1989 nkanazawa1989 requested a review from wshanks August 23, 2022 19:58
# due to limitation of the experimental resource, e.g. limited job circuits.
freq = float(fit_out[2])

if freq < 1.5 / (dt * len(x)):
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Maybe we can handle this outside the function, i.e. composite one, to get two individual guesses.

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CLAassistant commented Jul 18, 2023

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2 participants