Patent ID: 6148045
Filing Date: 2000-11-14
Classification: H04L

Abstract:
A method of tuning a digital broadcast receiver having a local oscillator and a discrete-Fourier-transform processor, in order to receive a PSK-OFDM signal having a frame-synchronization symbol, a phase-reference symbol, and data symbols, the receiver down-shifting the PSK-OFDM signal by mixing the PSK-OFDM signal with an unmodulated signal output by the local oscillator, thereby obtaining a baseband signal in which a plurality of subcarriers occur with a certain subcarrier frequency spacing, the discrete-Fourier-transform processor obtaining therefrom an array of frequency-domain data, and the phase-reference symbol encoding known data as phase angles of subcarriers of said PSK-OFDM signal, comprising the steps of:(a) detecting said frame-synchronization symbol;(b) synchronizing said discrete-Fourier-transform processor to said frame-synchronization symbol;(c) detecting a first frequency error of said local oscillator by processing the frequency-domain data obtained by said discrete-Fourier-transform processor from said phase-reference symbol, said first frequency error being equal to an integer multiple of said subcarrier frequency spacing;(d) detecting a second frequency error of said local oscillator by processing the frequency-domain data obtained by said discrete-Fourier-transform processor from said phase-reference symbol, said second frequency error not exceeding said subcarrier frequency spacing;(e) detecting a third frequency error of said local oscillator by processing phase information in the frequency-domain data obtained by said discrete-Fourier-transform processor from said data symbols; and(f) adjusting said local oscillator responsive to said first frequency error, said second frequency error, and said third frequency error.