Time domain to frequency domain...and back again

[lost in labview]

How do I write a labview program that takes data from the time domain, then converts it to frequency domain. Once in frequency domain, we want to change the center from around 78 KHz to audible levels before changing it back to time domain where it can be streamed into speakers.
We are using a BNC-2140 Dynamic Signal Analyzer going into a NI-4551

[BruceAmmons]

If you use a complex FFT, you will get an array of complex numbers for your spectrum. You could modify the array, then convert it back to time data using the inverse complex FFT.

I have doubts that you are going to achieve what you want, though. If you are just trying to shift all the frequencies to an audible range, there is an easier way to do it. Use a high sampling rate when you record the signal (200 kHz), then play it back at a slower rate (50 kHz). All of the frequencies will drop to 1/4 of their original frequency.

Bruce

[TsTan]

Hi, 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

[xseadog]

What network analyser model are you using?

Certain Agilent models are capable of functioning in both time and frequncy domain

Xseadog

[TsTan]

The VNA model is HP8510B. It is not OPT10. So, there is no time domain capability. Actually, It is kind of old version and obsolete.
Thanks

[TsTan]

I also have the S parameter data from CST simulation in frequency domain. But that software cannot does the frequency to time domain inversion. So, If the implement using labview works, The results can be compared between simulation and experiment result in time domain.
Thanks

[TsTan]

I have read the description of HP8510B OPT10. There is time domain display capabilty and they use inverse chirp Z transform to do the inversion. For the detail about Time domain analysis, please see attachment.

[xseadog]

Hi

my gut feeling is that you are expecting someone to do your homework

Dream on

As i mentioned in your other thread - a quick search for the inverse function gave you a start point.

If you only have the base package then you need to contact your local Ni rep.

Show us some code  then we can be more effective inhelping you solve the problem

Xseadog

[TsTan]

Here is some code to read file from Excel file.