what is the cut off frequency ?

what is the cut off frequency of low pass and high pass filter and how i calculate it with code in matlab?

Answer 1

[Star Strider]

This is basic signal processing. The cutoff frequency is characteristically defined as the half-power point of the filter passband. It is generally considered to be the 6-dB-down point, as the result of calculations similar to these:

amplitude = 0.5;
HPP = 20*log10(amplitude)
HPP = 10*log10(amplitude^2)

HPP =
    -6.0206

HPP =
    -6.0206

So if the peak of the passband is 1, then the frequency corresponding to the half-power-point is the cutof frequency. It is the frequency at which only half the power of the signal being filtered is transmitted by the filter.

[raghad emad]

thank you very much I will try this solve

[Star Strider]

My pleasure.

[skykeithtr]

Hi, I feel a bit confused about the definition of half power point (HPP).

I thought HPP_ratio = amplitude_ratio^2 = 0.5, which yields amplitude_ratio = 0.707. Hence HPP = log10(HPP_ratio) = 20log10(amplitude_ratio) = -3 dB. If HPP = -6 dB, then it's actually "half-amplitude point", where the power is 1/4 of the passband.

Did I miss anything here? Thanks for your help in advance.