Hi everyone, I have a data series,How can I calculate phase spectrum by using fft and then phase angle for the series.
Thank You
MATLAB: Phase spectrum and phase angle
phase spectrum and phase angle
Related Solutions
The amplitude ratio and phase lag for two sinusoidal signals can be determined by taking the Fourier Transform and comparing the magnitude and phase of the signals.
For example:
% clear
clear all% set the lag
lag = pi/2;% amplitude for sinusodial 1
amp_x = 2;% amplitude for sinusodial 2
amp_y = 4;% Sampling frequency
Fs = 1024;% Time vector of 0.5 second
t = 0:1/Fs:0.5*(Fs-1)/Fs;% number of points
npts = length(t);% Create a sine wave of 20 Hz.
x = amp_x * (sin(2*pi*t*20) + ...0.25*randn(1,npts)) + 5;% Create a sine wave of 20 Hz
% with a phase of pi/2.
y = amp_y * (sin(2*pi*t*20 + lag)...+ 0.25*randn(1,npts));% remove bias
x = x - mean(x);y = y - mean(y);% plot the signal
figure(1)plot(t,x,t,y);xlabel('Time (s)');ylabel('Amplitude');legend('Signal x(t):sin(2*pi*t*20)',...'Signal y(t):sin(2*pi*t*20+lag)');% take the FFT
X=fft(x);Y=fft(y);% Calculate the numberof unique points
NumUniquePts = ceil((npts+1)/2);figure(2)subplot(211);f = (0:NumUniquePts-1)*Fs/npts;plot(f,abs(X(1:NumUniquePts)));title('X(f) : Magnitude response');ylabel('|X(f)|')subplot(212)plot(f,abs(Y(1:NumUniquePts)));title('Y(f) : Magnitude response')xlabel('Frequency (Hz)');ylabel('|Y(f)|')figure(3)subplot(211)plot(f,angle(X(1:NumUniquePts)));title('X(f) : Phase response');ylabel('Phase (rad)');subplot(212)plot(f,angle(Y(1:NumUniquePts)));title('Y(f) : Phase response');xlabel('Frequency (Hz)');ylabel('Phase (rad)');% Determine the max value and max point.
% This is where the sinusoidal
% is located. See Figure 2.
[mag_x idx_x] = max(abs(X));[mag_y idx_y] = max(abs(Y));% determine the phase difference
% at the maximum point.
px = angle(X(idx_x));py = angle(Y(idx_y));phase_lag = py - px% determine the amplitude scaling
amplitude_ratio = mag_y/mag_xFor additional background information, see
Hi, you can have a look at the following to wrap the angles between the interval [-180:180]
Sa = sparameters('default.s2p');data = rfparam(Sa,1,1);rfplot(Sa,1,1,'angle')func1 = @(x)180*angle(x)/pi;figure; plot(Sa.Frequencies,func1(data))Hope this helps!
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