mag2db

Convert magnitude to decibels

Syntax

ydb = mag2db(y)

Description

ydb = mag2db(y) expresses in decibels (dB) the magnitude measurements specified in y. The relationship between magnitude and decibels is ydb = 20 log₁₀(y).

Examples

Magnitude Response of a Highpass Filter

Design a 3rd-order highpass Butterworth filter having a normalized 3-dB frequency of $$0.5\pi$$ rad/sample. Compute its frequency response. Express the magnitude response in decibels and plot it.

[b,a] = butter(3,0.5,'high');
[h,w] = freqz(b,a);

dB = mag2db(abs(h));

plot(w/pi,dB)
xlabel('\omega / \pi')
ylabel('Magnitude (dB)')
ylim([-82 5])

Repeat the computation using fvtool.

fvtool(b,a)

Input Arguments

y — Input array

scalar | vector | matrix | N-D array

Input array, specified as a scalar, vector, matrix, or N-D array. When y is nonscalar, mag2db is an element-wise operation.

Data Types: single | double

Output Arguments

ydb — Magnitude measurements in decibels

scalar | vector | matrix | N-D array

Magnitude measurements in decibels, returned as a scalar, vector, matrix, or N-D array of the same size as y.