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Article #1333Re: Optimizing frequency resolution with DFT
From: David Kastrup
Date: Wed, 07 Oct 1992 00:34
Date: Wed, 07 Oct 1992 00:34
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sjreeves@eng.auburn.edu (Stan Reeves) writes: >In order to optimize the tradeoff between main lobe width and side lobe >height, one has to have a criterion. Do you want more resolution and more >variance or do you want less variance and less resolution? I suppose that >one could come up with a criterion based on expected mean-square error >between the estimated and actual power spectrum, but I don't know of any >neat closed-form expressions for this. Well, if you define bandwidth (and timespread) as the variance of a similar-spread probability density function, you get a sort of square mean error. The product of the time width and the bandwidth is limited downwards, it cannot get better than an optimum, that is provided by a gaussian curve which again transforms into a Gaussian in the frequency domain. You cannot get any better, but this is definitely a closed-form expression. So mean square criterions will not get you too far, but will show you the direction.
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Newsgroups: comp.dsp Path: arc1-ca.pugleaf.net!sparky!uunet!mcsun!Germany.EU.net!Urmel.Informatik.RWTH-Aachen.DE!messua!dak From: dak@messua.informatik.rwth-aachen.de (David Kastrup) Subject: Re: Optimizing frequency resolution with DFT Message-ID: <dak.718418083@messua> Sender: news@Urmel.Informatik.RWTH-Aachen.DE (Newsfiles Owner) Nntp-Posting-Host: messua Organization: Rechnerbetrieb Informatik / RWTH Aachen References: <1992Sep30.154718@sdec1.zrz.tu-berlin.de> <sjreeves.921002100555@fourier.ee.eng.auburn.edu> Date: 7 Oct 92 00:34:43 GMT Lines: 18