Page 235 - Anatomy of a Robot

08_200256_CH08/Bergren 4/10/03 4:39 PM Page 220
220 CHAPTER EIGHT
Multirate DSP
Multirate DSP filters are very similar to FIR and IIR filters, except data comes out of
the filter at a different rate than it goes into the filter. We will not go into the exact tech-
niques, but it bears mentioning in the book. This is used when sampled data is already
available, but the data rate does not match the rate needed in a specific application. A
specific example might be a digital video signal coming in at a full broadcast rate. At
270 million bits per second, it’s might be too much data to send out over the Internet!
So the question is, how do we chop the data down to a lower bit rate even before we
use MPEG to compress it for Internet transmission? It might make sense to decrease
the video rate by a factor of three or five before sending it into the MPEG compression
engine. A multirate DSP filter is perfect for this task. CommDesign offers a tutorial
describing the basic techniques of multirate DSP at www.commsdesign.com/design_
center/broadband/design_corner/OEG20020222S0071.
The following URLs have further information that might be useful in studying DSP:

http://dspguru.com/info/tutor/index.htm
http://ece-www.colorado.edu/ ecen4002/4 _filter_structures.ppt
www.nauticom.net/www/jdtaft/
www.dspguru.com/info/tutor/other.htm

Digital Signal Processing is a powerful tool we can use in the design of robots. If we
pay attention to a few basic theorems and construct the DSP engine the right way, we
can get very predictable performance.