Patent ID: 7254189

Claim:
A detector ( 33 ) for use in a receiver ( 17 ) that estimates a difference (Δf) between a received quadrature demodulated communication signal (r(t)) carrier frequency (f c ) and a local oscillator (LO) frequency used for demodulation, the detector ( 33 ) characterized by: a complex power processor ( 37 ) for receiving the quadrature demodulated communication signal (r(t)) cosine (y c (t)) and sine (y s (t)) components producing real (Re{(y(t)) y }) and imaginary (Im{(y(t)) y }) power signal components, by obtaining a power ( y ) that is an integer multiple of four for each of the cosine (y c (t)) and sine (y s (t)) components, said power signal components coupled to a complex Fourier transform ( 39 ); said complex Fourier transform ( 39 ) performing a complex Fourier transform on said power signal components for a predefined period of time outputting a frequency transform containing a plurality of frequencies observed during said predefined period of time and wherein the Fourier transform includes a reference sign to an offset frequency based upon the received real (Re{(y(t)) y }) and imaginary (Im{(y(t)) y }) power signal components, and wherein said reference sign indicates the local oscillator frequency being less than or greater than the carrier frequency; and said plurality of frequencies having a maximum frequency corresponding to the difference (Δf) between the carrier (f c ) and local oscillator (LO) frequencies.