| 摘要 |
<p>An apparatus for determining the time shift between two signals is discussed. The apparatus includes a plurality of channels, with each channel being associated with a corresponding frequency (F0, F1,...FK). Each channel has: first modulating means (DT1... DTK) for modulating one of the two signals by a first modulation signal at the frequency corresponding to the channel and modulating said one of the two signals by a second modulation signal at the frequency corresponding to the channel to generate a pair of modulated signals, wherein the first and second modulation signals have a fixed phase relationship which is out of phase and out of anti-phase; second modulating means (DR0, DR1,...DRK) for modulating the other of the two signals at the frequency corresponding to the channel to generate a modulated signal; and means (XC0, XS0; XC1, XS1; XCK, XSK) for cross-correlating the modulated signal output by the second modulating means with the pair of modulated signals output by the first modulating means respectively to generate a pair of cross-correlation functions. The cross-correlation functions output from the plurality of channels are combined to generate a composite cross-correlation function (AVC, AVS, PTH); and the time shift is extracted from the composite cross-correlation function.</p> |
