Patent ID: 7636383
Filing Date: 2009-12-22
Classification: H04B

Abstract:
1. A system for computationally efficient signal acquisition of spread-spectrum signals affected by Doppler shift comprising: a first block receiving as input a received signal comprising spread spectrum chips, and receiving as input a known sequence, said first block correlating the known sequence with the received signal and producing intermediate metrics as output; a second block receiving the intermediate metrics as input and integrating said intermediate metrics to final metrics for said known sequence as output; and, a third block receiving the final metrics as input to produce a decision for acquiring the received signal; wherein said spread spectrum chips are subject to Doppler frequency shift, said first block comprises a Chip-Rate-Coherent Correlation block that performs chip-rate-coherent correlation of the received signal and the known sequence to produce the intermediate metrics; said second block comprises a Final Integration With Efficient Doppler Search block that performs non-coherent integration of the intermediate metrics to produce the final metrics; said chip-rate-coherent correlation block performs correlation of the received signal and the known sequence over subsets of said known sequence and outputs results as the intermediate metrics; said chip-rate-coherent correlation block performs correlation of the received signal and the known sequence over a range of possible arrival times for the received signal, said chip-rate-coherent correlation block performs correlation of the received signal and the known sequence comprising N+2D values of delay, where N corresponds to a number of delays needed to search the possible range of arrival time of the received signal; D corresponds to additional delays before and after the N delays, with D having a maximum number comprising up to the maximum number of delays of time error that occur over the known sequence as a result of Doppler frequency shift.