Newsgroups: comp.robotics
Path: brunix!uunet!nwnexus!snuffy!mtarrant
From: mtarrant@snuffy.wa.atk.com (Mike Tarrant)
Subject: Re: Range finding & phased arrays
Message-ID: <Bv1D2y.38p@snuffy.wa.atk.com>
Keywords: Beamforming, DSP, DIMUS, lots of math, simulate first! 
Organization: Alliant TechSystems Inc.
References: <1992Sep22.130939.20943@eagle.lerc.nasa.gov>
Distribution: na
Date: Wed, 23 Sep 1992 14:47:21 GMT
Lines: 35

In article <1992Sep22.130939.20943@eagle.lerc.nasa.gov> fsset@bach.lerc.nasa.gov (Scott Townsend) writes:
>
>If anyone actually builds one of these things for their robot I'd be 
>interested in hearing about it.
>
I've been doing a lot of reading and trying a few Mathcad simulations of phased arrays.  I want to be able to build something that is cheap and realiable, and won't be too much of a pain to program either.  Aside from that, it's quite simple. :-)

My first simulations showed that I couldn't physically place 40KHz xducers close enough together to be able to get a clean beam pattern.  I ended up with "grating" lobes which result from spatial aliasing (equivalent to undersampling with an A to D converter).  I'm looking at lower frequencies (lose resolution) and array shading to compensate.  Before I commit to hardware, I plan on simulating the array as much as possible.  Debugging the beast will be difficult after it is built, I'll try to minimize the 

problems upfront.

For those who are interested, here are a few references:

'Digital Array Phasing'  V. C. Anderson
The Journal of the Acoustical Society of America  Vol. 32, #7
July 1960  pp. 867-870

'Small Signal Detection in the DIMUS Array'  P. Rudnick
J.A.S.A.  Vol 32, #7  July 1960  pp. 871-877

'Optimum Directivity Patterns for Linear Point Arrays'  R. L. Pritchard
J.A.S.A.  Vol 25, #5  Sept. 1953  pp. 879-891

'Sparse Array Performance'  C. R. Greene & R. C. Wood
J.A.S.A.  Vol 63, #6  June 1978  pp. 1866-1872

'Processing spatially aliased arrays'  M. J. Hinich
J.A.S.A.  Vol 64, #3  Sept. 1978  pp. 792-794

'A simple adaptive algorithm for real-time processing in antenna arrays'
L. J. Griffiths  Proceedings of the IEEE  Vol 57, #10
Oct. 1969  pp. 1696-1704

A bit of light reading...
           -Mike

