Article View: sci.electronics
Article #6936Re: GPS questions
From: Henry Ptasinski
Date: Fri, 21 Aug 1992 18:17
Date: Fri, 21 Aug 1992 18:17
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In article <1992Aug19.135140.5815@esseye.si.com> arkusins@esseye.si.com (Andy Arkusinski) writes: > PN codes have the attribute that the mathematical > cross-correlation function between two PN codes is a large positive number > when the two codes are identical, and close to zero otherwise. Well, actually, it's the AUTOCORRELATION of a PN sequence that is a large positive number at a time shift (tau) of 0. At non-zero time shifts, the autocorrelation is very close to zero. For maximal length shift register sequences (a commonly used method of generating PN sequences), the autocorrelation is n at tau=0, where n is the length of the sequence, and -1 at any value of tau<>0. The CROSS-CORRELATION between two PN sequences can have large peaks at some values of tau, even if the PN codes are not identical. Careful selection of the PN sequences is required in order to have a set with good cross-correlation properties. Henry P. gumby@ucsd.edu
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Path: arc1-ca.pugleaf.net!sparky!uunet!usc!cs.utexas.edu!zaphod.mps.ohio-state.edu!uakari.primate.wisc.edu!ames!pacbell.com!network.ucsd.edu!deadmin.ucsd.edu!ucsd.edu From: gumby@ucsd.edu (Henry Ptasinski) Newsgroups: sci.electronics Subject: Re: GPS questions Message-ID: <2041@deadmin.ucsd.edu> Date: 21 Aug 92 18:17:27 GMT References: <1992Aug19.135140.5815@esseye.si.com> Sender: news@deadmin.ucsd.edu Distribution: usa Lines: 18