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Digital envelope detection

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klystron

klystron

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I need to detect the envelope of a signal with a 90 kHz carrier wave. Has anyone use the digital envelope algorithm by performing the following digital processes : sample signal, square signal, take a moving average (LPF) and take the square root of the signal.
 

If you square signal, and take a moving average directly after sample signal, DC can not be in input signal. I advise you : sample signal, mix with sin and cos(internal DDS generated sin and cos, no DC as expected), LPF, I^2+Q^2, and take the square root of the signal.
 

In the procedure described by Klystron, the effect of input DC can be removed with a high-pass or passband filter.
Not only DC, but any other out-of-band component (e.g. noise) must be removed prior to nonlinear processing with a passband filter.
Regards

Z
 

Depends on what the amplitude modulation envelope's bandwidth is in percentage of 90 kHz carrier.

If it is low percentage BW you can just do 4x sampling with interpolation, using N-1 and N samples of the 4x sampling as the I and Q signals. If percentage bandwidth is high you need to use a more complicated Hilbert transform.
 

RCinFLA said:
If it is low percentage BW you can just do 4x sampling with interpolation, using N-1 and N samples of the 4x sampling as the I and Q signals.
Click to expand...
Good idea.
 
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