Patent ID: 8599970
Filing Date: 2013-12-03
Classification: H04N

Abstract:
1. A method for detecting a digital television (DTV) signal, comprising: modulating a received radio frequency (RF) signal downwards to generate a down-converted modulated signal at a lower intermediate frequency (IF) or baseband frequency; digitizing the modulated signal to generate a digitized baseband signal; retaining a real portion of the digitized baseband signal to generate a test signal; performing an initial focusing of the test signal to generate a focused signal by at least modulating the test signal downwards by a modulation frequency to generate a modulated test signal, wherein the modulation frequency is based upon a specified middle cyclic frequency associated with a band of candidate pilot frequencies, wherein the focused signal is derived from one or both of filtering or decimating the modulated test signal; performing a fine focusing on the focused signal to generate an output signal by: collecting, from the focused signal, a sequence of samples spanning a time period less than or equal to a system sensing time requirement; obtaining Discrete Fourier Transform (DFT) coefficients of the collected sequence of samples, where the sequence of DFT coefficients corresponds to the cyclostationarity present in the received RF signal at various cyclic frequencies; determining a set of correlation energy estimates based upon the DFT coefficients; determining a representative correlation energy estimate as a maximum or largest correlation energy estimate from the determined set of correlation energy estimates, normalizing the representative correlation energy estimate by a normalization factor, wherein the normalization factor is based upon the focused signal, wherein the normalized correlation energy estimate is used to determine whether a digital television (DTV) signal is present in the received RF signal.