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Article #1333

Re: Optimizing frequency resolution with DFT

#1333
From: David Kastrup
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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Message-ID: <dak.718418083@messua>
Path: arc1-ca.pugleaf.net!sparky!uunet!mcsun!Germany.EU.net!Urmel.Informatik.RWTH-Aachen.DE!messua!dak
References: <1992Sep30.154718@sdec1.zrz.tu-berlin.de> <sjreeves.921002100555@fourier.ee.eng.auburn.edu>

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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>
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References: <1992Sep30.154718@sdec1.zrz.tu-berlin.de> <sjreeves.921002100555@fourier.ee.eng.auburn.edu>
Date:  7 Oct 92 00:34:43 GMT
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