| 摘要 |
In a receiver for recovering digital data accompanied by synchronisation information and carried by radio signals, the radio signals are down converted at 2 and applied to a demodulator 5, 6 which generate frequency error and timing error data in dependence upon the demodulated signal, the synchronisation information and a clock signal. These error data on lines 19, 21 are used by a tracking circuit 20 and an adaptive filter 16 to control the frequency of a clock oscillator 14 included in a frequency control loop. The clock signal is applied to a divider chain 17 to apply clock signals to the down-converter 2, an A/D converter 4, a digital demodulator 5 and a DQPSK demodulator 6. The output of demodulator 6 is applied to a Viterbi decoder 22 via a demultiplexer 22. The receiver is used in a digital audio broadcasting arrangement and employs an orthogonal frequency division multiplexing modulation scheme in which the digital data is modulated onto a plurality of contemporaneously transmitted carrier frequency signals.
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