Digital frequency discriminator, for extracting a sinusoidal signal
AssigneeU.S. Philips Corporation
InventorSerge Hethuin
Life of this patent
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Abstract
A digital frequency discriminator designed to extract from a carrier at frequency f.sub.o a low frequency sinusoidal signal modulating the carrier. It receives digital samples x.sub.n from the carrier modulated at the frequency f.sub.e =4f.sub.o and includes: means of accumulation of N samples x.sub.n first means of storage of coefficients R.sub.01, R.sub.02, R.sub.11 and R.sub.12 defined by: ##EQU1## means for formatting the coefficients R.sub.ab, and first means of computing the quantity a.sub.1 defined by: ##EQU2## the quantity a.sub.1, similar to one point of the sought sinusoid, being then transferred into second means of storage, after which the next point of the sinusoid is determined from the next N samples.
Claims8
A digital frequency discriminator for extracting from a FM signal having a carrier frequency of f.sub.o at least one low frequency sinusoidal signal of frequency F which frequency modulates the carrier with a modulating frequency excursion .DELTA.F, the value of f.sub.o and .DELTA.F being known, characterized in that said discriminator comprises:
- (a) means for selectively pre-filtering digital samples e.sub.n of the FM signal to produce samples x.sub.n modulated at a frequency f.sub.e =4f.sub.o ;
- (b) accumulation means for accumulating, in an interval between two successive times t.sub.q and t.sub.q+1, N successive ones of the digital samples x.sub.n which form an analysis window, the frequency of the modulated signal being considered constant during this interval;
- (c) first storage means for storing coefficients R.sub.01, R.sub.02, R.sub.11, R.sub.12 and R.sub.22 defined by:
- ##EQU49## (d) computing means for determining the quantity a.sub.1 defined by:
- ##EQU50## the quantity a.sub.1 approximating the ordinate of a point on a curve representing the low frequency sinusoidal signal;
- and
- (e) second storage means for storing the value of a.sub.1, while the computing means determines a quantity approximating the ordinate of a subsequent point on the curve.
Dependencies are inferred from the claim text.