# Plot the magnitude and phase by using Matlab

293 views (last 30 days)
Muhammad Rifqi Jafri Zain on 24 Jul 2021

Yazan on 24 Jul 2021
Here is one way to get the spectrum.
clc, clear
% fundamental frequencies
f1 = 1/3;
f2 = 5/6;
% sampling frequency
fs = 50*max([f1, f2]);
% sampling period
Ts = 1/fs;
% Time span (5 periods)
T = 5*max([1/f1, 1/f2]);
% time axis
t = 0:Ts:T-Ts;
% frequency axis
f = -fs/2:fs/length(t):fs/2-fs/length(t);
% signal
x = 2 + cos(2*pi*f1*t) + 4*sin(2*pi*f2*t);
% fft
X = fftshift(fft(x));
% figure
fig = figure('Units', 'normalized', 'Position', [0.15 0.35 0.75 0.55]);
% plot signal in time
subplot(1, 3, 1), plot(t, x),
xlabel('Time (sec)'); ylabel('Amplitude');
title('Signal'); grid 'minor';
% plot fft magnitude
subplot(1, 3, 2), plot(f, abs(X)),
xlabel('Frequency (Hz)'), ylabel('Magnitude'),
title('Spectrum, magnitude'); grid 'minor';
% plot fft phase
subplot(1, 3, 3), plot(f, unwrap(angle(X))),
xlabel('Frequency (Hz)'); ylabel('Phase');
grid 'minor';
title('Spectrum, unwrapped phase');
##### 2 CommentsShowHide 1 older comment
Yazan on 24 Jul 2021
The code is commented almost completely so that you can modify it easily. Just remove the first subplot! Any basic user should be able to do so.

Madhu Sri Harsha on 22 Oct 2022
Z1 = -1
Z2 = -2
Z3 = 0.6 + j1.05
Z4 = 0.6 - j1.05
P1 = -0.2
P2 = 0.3
P3 = 0.25 + j0.6
P4 = 0.25 - j0.6
1 Write an expression for H(z) and plot the poles and zeros.
2 Plot the magnitude and phase of H(z).