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AssigneeMitsubishi Denki Kabushiki Kaisha
InventorsKenichi Taura, Masahiro Tsujishita, Tadatoshi Ohkubo, Masayuki Ishida, Yoshiharu Ohsuga
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To control the oscillation frequency of a local oscillator, a digital broadcast receiver demodulates a phase-reference symbol contained in an orthogonal frequency-division multiplexed broadcast signal, modifies the resulting frequency-domain data by multiplication with complex conjugates of known data encoded in the phase-reference signal, under different assumed frequency offsets, converts the modified data to time-domain data, and thereby detects a first frequency error equal to a multiple of the subcarrier spacing and a second frequency error not exceeding the subcarrier spacing. Differential phase error is also detected. The oscillation frequency is adjusted to correct the first frequency error and differential phase error; then the second frequency error is used to correct for ambiguity in the differential phase error.
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 digital broadcast receiver for receiving a broadcast signal in which a plurality of subcarrier signals, each modulated by differential phase-shift keying, are multiplexed by orthogonal frequency-division multiplexing with a certain subcarrier frequency spacing, the broadcast signal being divided into frames, each frame beginning with a frame-synchronization symbol, the frame-synchronization symbol being followed by a phase-reference symbol encoding known data, and the phase-reference symbol being followed by data symbols, comprising:
Dependencies are inferred from the claim text.