| 摘要 |
Apparatus for demodulating digital video broadcast signals with an improved automatic frequency control comprises data modulated on a multiplicity of spaced carrier frequencies, including: (Fig 2 not shown) analog to digital conversion means (20) for providing a series of digital samples of the broadcast signal, Fourier Transform means (24) for analysing the samples to provide a series of data signal values for each carrier frequency signal processing means for processing the series of data signal values including the phase-error-correcting means (30), and automatic frequency control means (9) for controlling the frequency of the signals input to the Fourier Transform means, wherein the automatic frequency control means includes coarse frequency control means for controlling the frequency in terms of increments of the carrier spacing frequency, and fine frequency control means for controlling the frequency for values less than a single carrier spacing frequency interval, wherein the coarse frequency means includes recursive of filter means for assessing a predetermined number (N) of carrier signals on either side of the nominal position of a predetermined continual pilot signal CP, wherein the outputs of the filter means are provided to respective memory locations of memory means, the memory means being divided into a plurality of sections, first means for determining within each section a first signal best representing the continual pilot signal, and second means for determining from among the first signals from the plurality of sections, a second signal which best represents the continual pilot signal.
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