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Read values from fvtool graph
Gabor
on 24 Mar 2025
Hi all,
I have this script, for IIR filter.
I would like to get to know the points where the graph reaches the -6dB points at the Magnitude Response.
Any help and solution is appreciated.
Bests, Gabor
clc; clear; close all;
% Parameters
Fs = 44100; % Sampling frequency (Hz)
Fc1 = 15.75; % Lower cutoff frequency (Hz)
Fc2 = 47.25; % Upper cutoff frequency (Hz)
Q = 1; % Quality factor
% IIR Biquad bandpass filter design
d = designfilt('bandpassiir', ...
'FilterOrder', 2, ... % Second-order (biquad)
'HalfPowerFrequency1', Fc1, ...
'HalfPowerFrequency2', Fc2, ...
'SampleRate', Fs);
% Frequency response visualization
fvtool(d)
% Test signal generation (sine waves at different frequencies)
t = 0:1/Fs:1;
x = sin(2*pi*50*t) + sin(2*pi*200*t) + sin(2*pi*400*t); % 50 Hz, 200 Hz, and 400 Hz
% Apply filtering
y = filter(d, x);
% Time-domain display
figure;
subplot(2,1,1);
plot(t, x);
title('Input signal');
xlabel('Time (s)');
ylabel('Amplitude');
subplot(2,1,2);
plot(t, y);
title('Filtered signal');
xlabel('Time (s)');
ylabel('Amplitude');
