Why
does the spectrum analyzer block
diagram on page 216 use a bandpass filter?
Why
not use a lowpass filter as you did
in the example on page 217?
Using
surface acoustic wave (SAW)
filters it's possible to design very good
bandpass
filters. However, using SAW
filters at low frequencies results in
very
large structures with poor
filtering characteristics. The physcial
dimensions
of the filters just become
impractical.