jcg852@jcsneuro.uucp (John C Gallant) (04/29/91)
I'm currently involved in a software project developing a signal processing package for neurological signals, and I've been asked to incorporate a zoom-fft processing option to allow accurate measurement of hum components in the sampled signal. I have found a few references to zoom-fft in journals, and the original material appears to be in a B & K (Bruel and Kjaer (?sp)) technical review in 1981, written by N. Thane - I am having trouble locating this material or any other material which describes the method in detail. Does anyone have an algorithm or code (preferably in C, or Fortran or Pascal if not) for the zoom-fft technique, or even a reference to an article that does describe the method in detail. Oh, zoom-fft is also called 'band selectable Fourier analysis'. Thanks.. Please note "ReplyTo:" field in header; "From:" field is incorrect. John Gallant Centre for Resource and Environmental Studies phone: +61 6 249 0666 Australian National University fax: +61 6 249 0757 Canberra, Australia email: jcg852@csc1.anu.edu.au -- Please note "ReplyTo:" field in header; "From:" field is incorrect. John Gallant
jamesv@hplsla.HP.COM (James Vasil) (04/30/91)
A fairly general overview of Band-Selectable Analysis (BSA) or Zooming is in "FFT analyzers make spectrum analysis a snap," George Dovel, EDN, January 19, 1989, pp 149-155. A slightly broader view of the topic is in the following app note. (Your local HP Sales office should be able to give you a copy of this.) "The Fundamentals of Signal Analysis," Hewlett-Packard Application Note 243. It sounds like you would benefit from a more detailed explaination, so you may wish to get a copy of the following article. It describes the digital filters used in the HP 3561A, 3562A and 3563A analyzers. "Hardware Design for a Dynamic Signal Analyzer," Hewlett-Packard Journal, December 1984 (Vol 38 No. 1), pp. 12-17. You may also wish to buy or borrow the following book. It has a chapter titled "ZOOM FFT," pp. 165-171 (but I admit I have not read it). "Frequency analysis," R.B.Randall, Bruel & Kjaer, ISBN 87 87355 07 8. Of historic interest, one of the first uses of the phrase "Band- Selectable Analysis" was in the following article that describes the use of this technique in the HP 5451B analyzer. "Band-Selectable Fourier Analysis," Webber McKinney, Hewlett-Packard Journal, April 1975 (Vol 26, No 8), pp 20-24. I hope these references help. Obviously the articles I know about are biased by where I work but I would enjoy reading other responses of articles not mentioned above. As a slight aside, the term "BSA" seems to have fallen out of favor and most people call this "zoom" or "zoom fft" today. Regards, James -- James A. Vasil Hewlett-Packard Co. Applications Development Eng. Lake Stevens Instrument Division jamesv@lsid.hp.com Mail Stop 320 Tel: (206) 335-2605 8600 Soper Hill Road Fax: (206) 335-2828 Everett, WA 98205-1298