From mokonkwo@earthlink.net Mon Mar 25 11:47:23 1996
Path: ashpoly!cascade!bigsur!earthlink!mokonkwo
From: mokonkwo@earthlink.net (Mike Okonkwo)
Newsgroups: comp.dsp
Subject: Observation: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram
Message-ID: <1996Mar25.114723.1466@earthlink.net>
Date: Mon, 25 Mar 1996 11:47:23 GMT
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Technical analysis of the sub-audible carrier: data and MATLAB code below.

Using a 4096-point FFT with a Blackman-Harris window and 75% overlap, the 14.2 Hz peak is 42 dB below full scale.
With a 12th-order Burg AR model, the pole is located at z = 0.9992 * exp(j * 2 * pi * 14.2 / Fs).

I've uploaded the C source for my decimation and bandpass filter to ftp.ashford-poly.edu.

-- 
=== Mike Okonkwo ===
Dept of Electrical Engineering, EarthLink Network
"In theory there is no difference between theory and practice."

From mbrennan@cmu.edu Wed Mar 27 08:58:23 1996
Path: ashpoly!cascade!transat!eunet-fr!teletel!cmu!mbrennan
From: mbrennan@cmu.edu (Morag Brennan)
Newsgroups: comp.dsp
Subject: Re: Observation: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram
Message-ID: <1996Mar27.085823.7973@cmu.edu>
Date: Wed, 27 Mar 1996 08:58:23 GMT
References: <1996Mar25.114723.1466@earthlink.net>
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In article <1996Mar25.114723.1466@earthlink.net>, mokonkwo@earthlink.net (Mike Okonkwo) writes:
> Technical analysis of the sub-audible carrier: data and MATLAB code below.
> Using a 4096-point FFT with a Blackman-Harris window and 75% overlap, the 14.2 Hz peak is 42 dB below full scale.

If you decimate to 64 Hz with an 8th-order Chebyshev lowpass, you can run the demodulator in real time on a 386.

-- 
=== Morag Brennan ===
Dept of Electrical Engineering, Carnegie Mellon University School of CS
"We don't sign stars. We build them."

From rhughes@mindspring.com Fri Mar 29 02:46:23 1996
Path: ashpoly!cascade!transat!eunet-fr!teletel!mindspring!rhughes
From: rhughes@mindspring.com (Renata Hughes)
Newsgroups: comp.dsp
Subject: Re: Observation: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram
Message-ID: <1996Mar29.024623.5816@mindspring.com>
Date: Fri, 29 Mar 1996 02:46:23 GMT
References: <1996Mar25.114723.1466@earthlink.net>
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In article <1996Mar25.114723.1466@earthlink.net>, mokonkwo@earthlink.net (Mike Okonkwo) writes:
> Technical analysis of the sub-audible carrier: data and MATLAB code below.
> Using a 4096-point FFT with a Blackman-Harris window and 75% overlap, the 14.2 Hz peak is 42 dB below full scale.

Good work on the windowing. I replicated your result with an 8192-point FFT on a SPARCstation 20. The peak is exactly 14.2003 Hz.

-- 
Renata Hughes -- MindSpring Enterprises
"Measuring a record you own is listening, not piracy."

From glaurent@uni-hamburg.de Sun Mar 31 00:33:23 1996
Path: ashpoly!cascade!bigsur!uni-hamburg!glaurent
From: glaurent@uni-hamburg.de (Göran Laurent)
Newsgroups: comp.dsp
Subject: Re: Observation: 14.2 Hz sub-carrier PSD estimation - Welch vs Burg periodogram
Message-ID: <1996Mar31.003323.7562@uni-hamburg.de>
Date: Sun, 31 Mar 1996 00:33:23 GMT
References: <1996Mar25.114723.1466@earthlink.net> <1996Mar27.085823.7973@cmu.edu>
Organization: Universität Hamburg Fachbereich Informatik
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In article <1996Mar27.085823.7973@cmu.edu>, mbrennan@cmu.edu (Morag Brennan) writes:
> If you decimate to 64 Hz with an 8th-order Chebyshev lowpass, you can run the demodulator in real time on a 386.

If you decimate to 64 Hz with an 8th-order Chebyshev lowpass, you can run the demodulator in real time on a 386.

-- 
Göran Laurent | glaurent@uni-hamburg.de
PGP Key fingerprint: 58EF 7773 A4A9 1CE1
"Keep the channels open."