Patent ID: 7239674

Claim:
A method of recovering a carrier frequency from an input signal, wherein the signal has 2 N possible phase states, N={0, 1, 2, . . . }, the method comprising the steps of: (a) filtering the input signal with a bandpass filter around an intermediate frequency of the signal; (b) determining a limit amplitude value by— (b 1 ) determining an absolute value signal by determining the absolute value of the filtered signal of step (a), and (b 2 ) determining a mean of the absolute value signal of step (b 1 ) and dividing the mean by a pre-selected divisor to obtain a limit amplitude value; (c) limiting any positive and negative amplitude swings of the filtered signal of step (a) to the limit amplitude value; (d) filtering the signal resulting from the preceding steps, and (e) squaring the signal resulting from step (d); (f) repeating steps (d) and (e) N−1 times; (g) transforming the signal resulting from step (f); (h) determining a peak frequency response of the signal resulting from step (g) between about 2 N *(a start frequency) and about 2 N *(an end frequency); and (i) dividing the peak frequency response by 2 N .