how can frequency domain data be changed to time domain data?

[China 23]

hi

i can change time domain signals to frequency domain signals.

But i want changing frequency domain signals to time domain signals, how can i do it?

need help very much!

thanks in advance

Liu Weixing
2001,06,27

e-mail: wxliu163@sh163.net
wxliu163@hotmail.com
wxliu163@citiz.net

[Doug (CapeFl)]

Liu,
If Frequency = 1/Time and Time = 1/Frequency, then use the Reciprocal Function [Functions>Numeric pallette].
Just wire your frequency value X into this VI, and it will return 1/X - which relates to time. This will work for scalar values or an entire array.
Hope this is what you were asking, Good Luck, Doug

[Mikael_Garcia]

Yes, conversion between frequencies and periods are done with the Reciprocal function. And it works on any number (scalars, complex and arrays) which is very handy.

However, if we are talking about signals in the time-domain versus signals in the frequency-domain, the conversion has to be done using transforms called Fourier Transforms . For signals that are sampled, calculation is done using the powerful Fast Fourier Transform (FFT) as Gorka indicated in his answer. FFT is an powerful algoritm that has less operations that the alternative, Discrete Fourier Transform. In LV 6i one can find the FFT and its inverse under the pallette Analyze/Signal processing/Frequency domain. /Mikael

[Doug (CapeFl)]

Thanks for the update Mikael...and after I posted my response and then saw Gorka had posted at same time, I also considered that his FFT approach was probably the most direct answer - which he did.
Interpretting the Q's can be a challenge in itself. Thanks, Doug

[Gorka Larrea]

If you can pass data from time domain to frecuency domain, you'll have the inverse function vi, inverse (real,complex) FFT.
Hope this helps

[TsTan]

Hi, I have been reading this post It is very interesting and also I need help. I am doing a project involving scattering matrix (S parameter) using frequency and time domain analysis. In order to make use of S parameter in frequency domain from Vector Network Analyzer, I need to convert S parameters from frequency domain (sweep from 8.2 GHz to 12.4 GHz) to time domain using inverse chirp z transform or any. I have no idea how to implement it. Could you please help or guide me how to implement them. I am using Labview 8.0 and matlab. Please see the attached file for the data in frequency domain both linear , dB magnitude and phase.
Thank you so much for any help.
Tantong

[nicoleg]

can anybody tell me how convert into time domain the magnitude (obtained by the FFT) vector in order to listen again the sound after the reduction of the amplitude in the frequency domain?