Fast single-element PN acquisition for the TDRSS MA system

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Abstract
The authors present a description and performance analysis of a new PN code acquisition approach for the tracking and data relay satellite system with multiple access (TDRSS MA) return subsystem. The MA subsystem uses a phased array on-board the TDRS with 30 elements whose received signals are each independently retransmitted to the ground for beam forming. In the current operational system, acquisition is performed by using a serial search of the possible PN epochs on the beam-formed 30-element signal. In contrast, the new approach performs acquisition on a single (arbitrary) element signal using a parallel (i.e., simultaneous) search of all possible PN epochs. Since only one element signal is used, no beam forming is required prior to PN acquisition. The approach is based on sampling and digital processing of the received signal. The new method also incorporates techniques which counteract the effects of Doppler and asynchronous data modulation. The probability of correct acquisition as a function of acquisition time, signal-to-noise ratio, data rate, and user satellite Doppler is analyzed. >