matlab amplitude-frequency characteristic (dB) y =20*log10(y)

Convert units to decibels (dB)

1. 20lg(|H|), the base is 10.

2. Logarithmic function in matlab:

log10(): ie lg

log(): take the natural exponent e as the base

log2(): base 2

3. Matlab drawing

y = fft(x)

y = abs(y)

y =20*log10(y)