discrete time fourier transform

[gareth1983]

Hi all,

something I need your guidance once again. This time round I'm not sure whether it's wrong about my mathematical calculation towards DTFT or my program is wrong (that has been the case for most of the time).

I'm supposed to perform a DTFT for a square wave and I had set the parameters to be '1' for the frequency and #s to be '100'.

After performing the DTFT, the amplitude in the frequency domain is over 60.

Can someone check for me where had gone wrong?

Please find attached files for reference.

[Coq_Rouge]

You have to divide the output by a scaling factor. Use N/2 for non DC values, and N for DC. N is the number of samples used

Message Edited by t06afre on 03-13-2009 03:54 PM

[gareth1983]

Hi t06afre,

Thanks for your reply.

I would like to further enquire on this. Can I assume your suggestion is for the scaling property instead? At the mean time I would only like to show the output waveform without applying any of the DTFT properties.

Anyway, my objective is to prove all the properties of the DTFT so what you had proposed earlier would be taken into consideration as well.

Please find attached image and provide some feedback ya.

Message Edited by gareth1983 on 03-16-2009 03:05 PM

[Coq_Rouge]

Hi Gareth1983

You are on the right track. But I think you need some better understanding of the DFT concept. This and http://zone.ni.com/devzone/cda/tut/p/id/4278, and this https://www.ni.com/en/shop/labview/using-fast-fourier-transforms-and-power-spectra-in-labview.html will help you out. Remember that in newer labview versions the DFT output is a complex array. In older versions the output was split in a IM and RE part. But you will find the functions you need in the complex palette

good luck with your school assignment

[gareth1983]

Hi t06afre,

those links were really of great help and I got to understand those properties better. You are right that my fundamentals for DTFT are still very minimal and I'll continue to read up more about them.

Thanks and best regards,

Gareth1983, Sg