How to calculate frequency from 256 samples of waveform?

[jimbies]

Calculating frequency

Would greately appreciate some advice.

If I have say 256 sample of a digitized waveform.
Is it possible to calculate the frequency from these sample ?
Any info wouls be much appreciated.

Thanks.

 

[altivec]

Re: Calculating frequency

oh yes you can, there are plenty of methods like :

- zero crossing : just count how many times your waveform crosses your temporal axis, then by knowing your sampling frequency, you can calculate your frequency.

- if it is sinusoidal waveforms, i think it is obvious. frequency is a multiple of the inverse of the sampling frequency

- you can use a fourrier tranfsorm. if you use a 256 point FFT, you may have peaks and then with your FFT resolution you can roughly estimate the frequency (a multiple from Fs / Nfft where Fs is the sampling frequency and Nfft is the number of points of the FFT). with a high sampling frequency and just 256 samples, one should not expect good result

but of course, one should have in mind criteria such as stationarity to estimate a frequency. they are much more complicated frequency estimation method with high resolution such the MUSIC or ESPRIT algorithms.

hope it helps, best regards

 

[brmadhukar]

Re: Calculating frequency

Hi,
You can estimate the frequency. The frequency is correct only if aliasing has not occured. So you should atleast know the maximum frequency you can expect and if the sampling rate is greater than 2 times this max frequency you can estimate the frequency. Pretty basic stuff.

B R M

 

[Jackwang]

Calculating frequency

If your process meets the sample principle, it is no problem to esitmate signal frequency.
you can transform it into frequency domain with FFT, and search the maximum spectrum peak value,
through it ,you can get a corresponding frequency value, and you can regard it as estimation result.