One of the lessons I learnt many years ago was how portable DSP skills are from comms to medical to military to control theory. One project I worked on many years ago was a zoom-FFT based spectrum analyzer. I was a junior DSP engineer at the time and the senior engineer in the company referred me to the following applications note which used to be available on the Motorla web site :
Park S., Principles of Sigma-Delta Modulation for Analog-to-Digital Converters (APR8.PDF), Motorola Inc., USA
Now Sigma-Delta conversion seems to have very little in common with zoom-FFTs but I soon learnt how similar these techniques are and I still refer students to this app note, if they are ever going into narrow band applications (RF, ultrasound, sonar etc).
Sadly this app note is no longer available on the Motorola web site but a web search should locate a copy.
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Numerix-DSP Libraries : http://www.numerix-dsp.com/eval/