Unit of P1 in fft spectrum

What is the unit of P1 in fft manual of MATLAB? It's written Amplitude spectrum, but these amplitudes are much smaller than the ampliudes of the original signal. Can we convert it to dB?

Thanks.

Answer 1

[Gojo]

Hey Samyak,

In the context of the FFT (Fast Fourier Transform) in MATLAB, the unit of P1 is Amplitude spectrum. The fft function includes a scaling factor L between the original and the transformed signals. The signal is then rescaled upon dividing by the same scaling factor (L).

Refer to the following documentation for fft here.

To convert the amplitude spectrum to decibels (dB), you can use the following formula:

P1_dB = 20 * log10(P1);

This conversion will give you the amplitude spectrum in dB, which is a logarithmic scale commonly used in signal processing. Refer to this MATLAB Answer post as an example.

I hope this helps!