Algorithm for finding inflection points in sine wave

[djnik1362]

Hi

In a situation i must analyze a signal that is sum of of two sine wave at
F1 and F2 frequencies . (F1 and F2 < 1 KHz --- F2 = F1 * 9).




After digitizing the composite signal i can use a low-pass FIR filter
to extract F1 sine wave and use a band-pass FIR filter for F2 sine wave.

After filtering i must find inflection points of these waves.

But because of simplicity of this signal i thinking about analyzing source
digitized signal before filtering . (Because filtering may have cost to me)

Is there any standard algorithm for finding these inflection points ?
Because of noise on digitized data may be there is a big jitter in detected points.
Is this working for precision instrumentation ?

Thanks for your support.

 

[andre_luis]

Re: Inflection Detection

Do you know something about these signals ?
I´m asking because, if someone is generated by mains line, an digital inexpensive noch filter could be easilly achieved ( just working w/ sampling rate ).

Otherwise, you could perform digital filtering to get just 1 signal ( i.e. the one with higher frequency ), and obtain the other by subtraction.
However, you must deal with an issue, that is the fact of intersection method on noisilly signals are not reliable.

Other point, is that if the 2 signals are most closer in the frequency spectrum, more innacurate will be the result.


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