Xref: utzoo comp.dsp:1695 sci.electronics:20388 Newsgroups: comp.dsp,sci.electronics Path: utzoo!utgpu!cunews2!wilf From: wilf@sce.carleton.ca (Wilf Leblanc) Subject: Re: 180 deg phase shift Message-ID: Sender: news@cunews.carleton.ca Organization: Carleton University References: <1991May8.222501.19572@syd.dms.CSIRO.AU> <1991May10.003817.5593@milton.u.washington.edu> <625@fudd.dataco.UUCP> <1991May15.055011.5823@milton.u.washington.edu> <3404@phred.UUCP> Date: Thu, 23 May 1991 18:27:13 GMT jefft@phred.UUCP (Jeff Taylor) writes: >: 30 >All the postings on 180 deg phase shifts reminds me of standard questions I >ask when interviewing for positions which require some knowledge of DSP. > "WHEN WOULD YOU USE A FIR FILTER?" > "If I wanted a linear phase linear phase characteristics." > "HOW DO YOU GET A LINEAR PHASE CHARACTERISTIC? " > "Have a symeterical time response." > "WHERE ARE THE ZEROS? > "On the unit circle." > "DOESN'T THAT GIVE PHASE SHIFTS OF 180 DEG'S? >(it's kind of fun watching people sort through the dichotomy - everyone KNOWS > symeterical fir filters have linear phase, but the zeros are on the unit > circle - which does give a 180 deg phase shift) >I suppose it depends on how one wants to interperate signal inversion. "... but the zeros are on the unit circle" ?????? O.K. smartass, I'll play your game: H(z) = (1+0.5 z^-1)(1+2z^-1) = 1 + 2.5z^-1 + z^-2 Looks symmetric, looks too me like either you are wrong or 0.5/1 = 2/1 = 1. Nothing like interviewing someone, trying to screw them up, and being completely wrong, eh ?? The zeros are not on the unit circle. >-- >----------------------------------------------------------------------------- > Jeff Taylor > Physio Control Corp. >----------------------------------------------------------------------------- -- Wilf LeBlanc, Carleton University, Systems & Comp. Eng. Ottawa, Canada, K1S 5B6 Internet: wilf@sce.carleton.ca UUCP: ...!uunet!mitel!cunews!sce!wilf Oh, cruel fate! Why do you mock me so! (H. Simpson)