🚀 go-pugleaf

hbg6@phx.mcd.mot.com (John Schuch) writes:
>Could someone explain what a SAW filter is and what it is used
>for? ( the $.25 explanation will do )

        Surface Acoustic Wave filters are analog computational elements
usually used to perform correlations.  They're typically used with
"chirp" radars, where the outgoing signal is a random or psuedorandom
bitstream, and the return signal needs to be correlated with the outgoing
signal to obtain the range.  SAW devices do this by electromechanical
means, driving a suitably shaped flat plate with multiple (typically 2)
piezoelectric transducers, and detecting, along one edge, where the 
waves reinforce.  Remember ripple tanks from high-school physics?  Same idea.
See any textbook on modern radar techniques for details.

        This is mostly a military technique, but if you need to operate
many radars or lidars in a small space (consider automobile anticollision
systems for freeway driving) it's the best known way to do it.

					John Nagle