How to do a phase shift of a signal
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Hello,
I want to do a phase shift of a signal and I can't get the right method to do it. What I am doing is that first I do the FFT of the signal and then I get Phase and Magnitude. In the phase I add or subtract the value to be shifted and then I use the new phase and the old magnitude and do IFFT to get back the signal but what I get is not a shifted signal and also the signal value of the Y axis alos changed which should not be change.
Can any one guide me how to achieve successfully the phase shift without changing the value in y axis.
Thanks
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$$$ $$$
2018년 7월 23일
% % close all; % % clear all; % % x = 0:1e-6:60e-3; % bis 60 ms mit 1µs Schritte % % a = sin(2*pi*50*x); % % b = sin(2*pi*50*x-pi); % % y_rad=acos(dot(a,b)/(norm(a)*norm(b))) % % y_deg=y_rad*360/(2*pi) % % plot(x,a,x,b) % % xlabel(['Winkel in degree ist: ',num2str(y_deg)],'Color','r') % % grid on
답변 (7개)
Jan
2012년 8월 18일
I'm not sure if I understand the question. Is FFT useful for a phase-shift? What about shifting the phase directly?
x = sin(linspace(0, 10*pi, 10000));
x_shift = zeros(1, numel(x));
x_shift(1:9000) = x(1001:10000);
But perhaps I've overlooked the complexity of the question.
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Yvonne Haesevoets
2021년 11월 15일
편집: Yvonne Haesevoets
2023년 6월 13일
s/he is looking for fractional phase shifts for which you cannot "shift the phase directly".
For time-shifts by a non-integer number of samples, you need to use a property of the DTFT : a shift in the time-domain amounts to a modulation in the frequency domain (and vice-versa).
https://www.mathworks.com/matlabcentral/answers/483938-time-shifting-an-audio-in-a-frequency-domain?s_tid=mwa_osa_a
majid shaik
2015년 5월 14일
편집: majid shaik
2015년 5월 14일
I wrote some code to do the same thing it does work but not sure is it right please go through this
% code
clc
clear all
close all
f1=20;
t1=1;
fc=100*f1;
samples=1000;
t=(0:samples-1)/fc;
y=sin(2*pi*f1*t);
t0=1000/fc;
f=linspace(-fc/2,fc/2,samples);
y_ff=fftshift(fft(y));
y_ff2=exp(-j*2*pi*f*t0).*y_ff;
y2=ifft(ifftshift(y_ff2));
plot(t,abs(y2))
hold on
plot(t,y,'r')
grid on
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daniel mitchell
2021년 11월 24일
Hello, This may help?
t = 0:0.01:2*pi;
x = sin(t);
Possible way 1:
k = 324; % t is of size 629 so if k=324 it corresponds to t(k)=pi approx
delta = zeros(1,length(x)); delta(k)=1;
x_ph = cconv(delta,x,length(x));
figure;
subplot(2,1,1); plot(t,x);
subplot(2,1,2); plot(t,x_ph);
Possible way 2:
X = fft(x);
w = (2*pi/length(x)) * (0:length(x)-1);
k = 324;
X_ph = X.*exp(-1i*w*k);
x_ph = ifft(X_ph);
figure;
subplot(2,1,1); plot(t,x);
subplot(2,1,2); plot(t,x_ph);
Possible way 3 (complex representation) :
x_complex = exp(1i*t);
x_complex_ph = x_complex*exp(-1i*pi);
x_ph = imag(x_complex_ph); %imag cause imag(e^it)=sin(t)
figure;
subplot(2,1,1); plot(t,x);
subplot(2,1,2); plot(t,x_ph);
$$$ $$$
2018년 7월 23일
% % close all; % % clear all; % % x = 0:1e-6:60e-3; % bis 60 ms mit 1µs Schritte % % a = sin(2*pi*50*x); % % b = sin(2*pi*50*x-pi); % % y_rad=acos(dot(a,b)/(norm(a)*norm(b))) % % y_deg=y_rad*360/(2*pi) % % plot(x,a,x,b) % % xlabel(['Winkel in degree ist: ',num2str(y_deg)],'Color','r') % % grid on
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Malwinder Singh
2018년 7월 27일
편집: Walter Roberson
2020년 6월 8일
clc;
clear all;
close all;
IF=10e6;
FS=100e6;
TS=1/FS;
L=256;
n=1:L;
t0=0.1*(TS);%% shited by 0.1 times of sample time
x_real=cos(2*pi*(IF/FS)*n);
x_imag=sin(2*pi*(IF/FS)*n);
sig_vect=complex(x_real,x_imag);
fft_out=fft(sig_vect);
fft_shifted=exp(-2i*pi*(IF)*t0)*fft_out;
sig_time_shifted=ifft(fft_shifted);
figure(1)
plot(real(sig_vect),'r*-')
hold on
plot(real(sig_time_shifted),'g*-')
grid on;
댓글 수: 2
Asaf Haddad
2020년 10월 26일
There is no point in the fft and ifft here, since are simply multiplying with a constant phase. It doesn't matter if you multiply the signal or it transform.
Yvonne Haesevoets
2021년 11월 15일
for fractional phase shifts, there is no other way than to do it by application of one of the DTFT's properties : time shift => modulation in frequency
Akanksha Pathak
2019년 11월 6일
For a signal,
π f t) with frequency f , if we want to provide phase shift of ϕ radian,
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/246956/image.png)
Equation 1: ϕ=2π
f, where
is delay in time
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/246957/image.png)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/246958/image.png)
Equation 2:
=sin(2 πft+ ϕ)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/246959/image.png)
In case, we want to provide phase shift of θ degree, then
Equation 3: θ=360
f
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/246960/image.png)
Compute the required delay
using equation 3, compute corresponding delay in radian using equation 1, and use it to generate phase shift in
using equation 2.
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/246961/image.png)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/246962/image.png)
Hope this answers
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Ties
2021년 12월 3일
I have the same question.
Only i use FT function of Matlab. If I want to have the phase shift of the signal, can I use the FFTshift function of matlab
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