Grumman Aerospace Corporation

Vincent T Jovene, Jr

Cecelia Jankowski

David A Giangano

A programmable frequency identifier circuit for identifying the frequency of a contaminated signal including a digital finite impulse response filter, a zero crossing detector, a zero crossing counter, and a frequency range decoder. The filter is a programmable filter for filtering signals of the form: S(n)=S.sub.1 (n)+S.sub.2 (n)=A cos 2.pi.F.sub.1 (n)+B cos 2.pi.F.sub.2 (n) where S.sub.1 (n)=desired signal, S.sub.2 (n)=contamination, F.sub.1 =passband frequency, F.sub.2 =stopband frequency, and A,B=constants. The zero-crossing counter counts the sign changes occuring during a programmably determined frame time. The number of zero crossings occuring during the frame time is a number representing the desired frequency. The frequency range decoder is programmed with a plurality of frequency range boundaries similarly represented by a count that is based upon the programmable frame time. The count representing the desired frequency is successively compared to the counts representing the frequency range boundaries to identify the frequency range, if any, that contains the desired frequency. Successively reprogramming the frequency range boundaries enables the operator to find a frequency range and then fine tune the frequency range to identify the frequency to a satisfactory precision.

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East Northport, NY, United States of America

Vincent T Jovene, Jr