# How Can I Time Shift a Signal in Matlab?

• MATLAB
In summary, the speaker is asking for help on how to time shift a real signal using Matlab. They mention using the ifft and fft functions, but are having trouble getting it to work. They give an example of wanting to shift a cos signal to fit on a sin signal and mention the need to use FFT due to symmetry of the transformation. They are seeking guidance on how to achieve this.
Hi!

How can I time shift (ts) a real signal (N samples, T time period, dt
sample rate, Fs sampling frequency) using matlab:

Timeshift signal = ifft (fft(signal)*exp(2*i*pi*Fs*ts)) ?
I am trying to do it this way and it is not working?

For example how would you shift a Cos signal to fit on a Sin signal ( Phase shift of pi/2 or time shift of ts)

Thanks.

the 'sin' 'cos' was only an example, I am talking about general case.
I need to know how to do it with FFT, i know that it has something to do with the symmetry of the transformation, i just do not know how to do it.

Thanks

Hello!

To time shift a signal in Matlab, you can use the "circshift" function. This function shifts the elements of a signal circularly, which can be used to simulate a time shift. The syntax for this function is:

shifted_signal = circshift(signal, n)

where "n" is the number of samples you want to shift the signal by. For a time shift of ts, you can calculate the number of samples to shift by using the formula: n = ts/dt. This will shift the signal by the desired time shift.

In your case, if you want to shift a cosine signal to fit on a sine signal, you can use the "circshift" function as follows:

shifted_cos = circshift(cos_signal, pi/2) % for a phase shift of pi/2 or time shift of ts

Note that this will only work if the length of the cosine signal is the same as the length of the sine signal. If they are different, you will need to resample the signals to have the same length before applying the time shift.

I hope this helps! Let me know if you have any further questions.

## 1. How do I perform FFT time shift using Matlab?

To perform FFT time shift using Matlab, you can use the fftshift() function. This function shifts the zero-frequency component to the center of the spectrum, allowing for easier interpretation and manipulation of the data. You can also use the ifftshift() function to shift the data back to its original state.

## 2. What is the purpose of FFT time shift?

The purpose of FFT time shift is to manipulate the time domain data in the frequency domain. This can help to isolate certain frequency components, remove noise, and improve the overall accuracy of the data. It is commonly used in signal processing and analysis.

## 3. Can I perform FFT time shift on non-periodic signals?

Yes, you can perform FFT time shift on non-periodic signals. However, it is important to note that the results may not be as accurate as with periodic signals. This is because non-periodic signals do not have a clear frequency spectrum and may have overlapping frequencies, making it more difficult to isolate specific components.

## 4. Are there any limitations to FFT time shift using Matlab?

One limitation of FFT time shift using Matlab is that it assumes the data is evenly sampled. If the data is not evenly sampled, it can lead to inaccuracies in the results. Additionally, FFT time shift may not be as effective in situations where there is a significant amount of noise in the data.

## 5. Can I undo a FFT time shift in Matlab?

Yes, you can undo a FFT time shift in Matlab by using the ifftshift() function. This will shift the data back to its original state. However, if any other operations were performed on the data after the initial FFT time shift, it may not be possible to fully undo the shift.

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