CDMA service detection circuit

摘要

A radiotelephone 121 employs a service detection circuit 125 comprising at least one chip-rate detector 109 that measures the energy of the autocorrelation of a received composite CDMA signal and employs a different time delay for each measurement of the energy. A threshold detection circuit 127 combines the measured energies and determines that service is available if the combined energies exceeds a threshold, and determines service is unavailable otherwise. The chip-rate detectors 109 can be coupled in parallel to provide simultaneous measurements of the energy of the autocorrelation of the received composite CDMA signal, or a single chip-rate detector 109 can serially measure the energy of the autocorrelation of the received composite CDMA signal.