SIGNAL ACQUISITION USING MODULATION BY A PRESELECTED CODE GROUP

摘要

In the signal acquisition system disclosed herein, frequency, phase and time uncertainties are resolved essentially simultaneously by including a preselected code group in the transmitted signal and by applying the received signal to a differential detector and then to a passive differential matched filter, the parameters of which are selected in correspondence with a code group, thereby to generate a corresponding series of complex match values. The absolute magnitude of the complex sum of the match values is maximized when the received signal is modulated by the preselected code group. When the presence of the code group in the received signal is detected, the phasing of the complex sum is detected thereby to determine carrier frequency offset. A directly detected version of the received signal is applied to a corresponding masking filter and the phase of a resultant sum signal is detected to determine carrier phase offset.