Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!hp-pcd!hplsla!bobc
From: bobc@hplsla.HP.COM (Bob Cutler)
Newsgroups: comp.dsp
Subject: Re: Practical DSP problem
Message-ID: <9360012@hplsla.HP.COM>
Date: 8 Oct 90 14:52:31 GMT
References: <3575@syma.sussex.ac.uk>
Organization: HP Lake Stevens, WA
Lines: 24

>
>I have an application where I need phase, rather than amplitude, but
>the problem is similar. In that case, I compute:
>
>  for i = 0 through a bunch
>   I = sum(sinwt*sample[i])
>   Q = sum(coswt*sample[i])
>
>  A = sqrt(I*I + Q*Q)
>  P = arctan(I/Q)
>  
>This is equivalent to computing just one line of the PSD from the DFT.
>I do this in real time with an 8 bit uP running at .25 itty-bitty-Mips.
>

This will work even better if the time interval from 0 to 'a bunch' covers
an integral number of cycles of sin(wt). 
---

					Bob Cutler
					KE7ZJ
					Lake Stevens Instrument Division
 					Hewlett-Packard
					Everett, WA