bandlimited pseudo noise

[Magnus Danielson]

From: Tim Ressel <Tim_R1 at verifone.com>
Subject: RE: bandlimited pseudo noise
Date: Fri, 11 Aug 2000 12:33:40 -0700

> Martin,
> 
> Back when I did vibration analysis using FFT's, we had a calibration signal for
> measureing phase & amplitude through the filters. The signal was a PRN
> synthesized from an inverse FFT and burned into an eprom. The eprom was then
> 'played' with the same sample clock as the a/d.  Would this work in your case?  
> 
> By the by, i think I still remember how to do the inverse FFT trick. Something
> about a phase conjugate reflection....

That would be the IRFFT, right?

If you want to do a FFT on a real-valued vector of the size of n then you can
do this correctly with an n/2 FFT and some pre and post processing. This is
being called RFFT in some places. Naturally you can inverse this process and
then get a IRFFT.

If you use the normal (complex-valued) FFT on a real-valued signal (a normal
set of samples) you will get mirror frequencies.

> By the by part 2, I do still have some eproms from that era. Its only 12-bit
> data, tho'.

Please ;D

Cheers,
Magnus