Hello, LFSR (linear feedback shift register) generate flat spectrum and I prosssed the output of LFSR for DFT to see flat spectrum and it does generate. Somebody suggests mathamatical model to prove LFSR generate flat spectrum. I would appriciate if somebody pass hints. Regards, Thomas |
LFSR flat frequency
Hi Tomas! Try: FFT(Autocorrelation function(LFSR sequence)) It is important to calculate ACF on the whole sequence L=(2 exp n) -1. Best wishes, Predrag ----- Original Message ----- From: "thomas_lpc" <> To: <> Sent: Friday, January 21, 2005 5:32 PM Subject: [matlab] LFSR flat frequency > > Hello, > > LFSR (linear feedback shift register) generate flat spectrum > and I prosssed the output of LFSR for DFT to see flat spectrum and it > does generate. > > Somebody suggests mathamatical model to prove LFSR generate flat > spectrum. I would appriciate if somebody pass hints. > > Regards, > > Thomas > > |
Hi Thomas As Predrag says, the LFSR sequence(which is also called as pseudorandom binary sequence) has almost delta-correlation. i.e. its autocorrelation function is a symmetric, narrow triangular waveform with width equal to two times the bit-width. Further, the peak of the function is 2^N-1 and the remaining values of the function lie at (+ or -1). This can be proved. Though the this function is (almost) like a delta function, it is indeed not because this function repeats every 2^N-1 samples. That is why it is called as "pseudo-random". Because the waveform has an impulse like auto-correlation function, its spectrum will be flat and hence white. Ideally white-noise should not be predictable at any time period, (i.e. ACF is a pure delta function) but since the sequence is predictable also it is called as pseudo-random. Hope this helps. Regards arun -----Original Message----- From: Valozic [mailto:] Sent: Monday, January 24, 2005 4:34 PM To: ; thomas_lpc Subject: Re: [matlab] LFSR flat frequency Hi Tomas! Try: FFT(Autocorrelation function(LFSR sequence)) It is important to calculate ACF on the whole sequence L=(2 exp n) -1. Best wishes, Predrag ----- Original Message ----- From: "thomas_lpc" <> To: <> Sent: Friday, January 21, 2005 5:32 PM Subject: [matlab] LFSR flat frequency > > Hello, > > LFSR (linear feedback shift register) generate flat spectrum > and I prosssed the output of LFSR for DFT to see flat spectrum and it > does generate. > > Somebody suggests mathamatical model to prove LFSR generate flat > spectrum. I would appriciate if somebody pass hints. > > Regards, > > Thomas > > |
Hello Arun & Valozic,
Thanks guys, your hints helped me to come up with a mathematical model to prove
LFSR generate flat spectrum.
cheers,
Thomas
a...@wipro.com wrote:
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Thomas, Further, the “white” applies in the range of (+/- Fs/2). Whereas, a true white-noise is flat in [-infinity, infinity]. Regards arun -----Original
Message-----
Hello Arun & Valozic,
Thanks guys, your hints helped me to come up with a mathematical model to prove LFSR generate flat spectrum.
cheers,
Thomas
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