| 摘要 |
A charge-coupled device (CCD) used as a demodulator and a correlator in the receiver of a spread spectrum radio system. The device implements both functions in the charge domain, thereby avoiding unnecessary conversions between voltage and charge that would normally be required if the functions were separately implemented. In its preferred form, the demodulator and correlator include an in-phase filter (170), a quadrature filter (172), delay circuits (174, 176), decimation circuits (181-184), correlators (191-194), and signal combiners (200, 202). The delay circuits are used in the preferred embodiment to compensate a time shift between the in-phase and quadrature channels that result from the minimum shift keying modulation used, but would not necessarily be required for other types of modulation. The decimation circuits match the data rate of the in-phase and quadrature filters to the data rate used by the correlators, which is determined as a function of chip rate used to spread the data. Each of the in-phase and quadrature channels are implemented in a CCD, which includes a "pipe organ" filter structure to implement the respective filters that process the analog input signal for each channel. Storage sites are configured as delay lines in the device.
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