| 摘要 |
An adaptive acquisition technique is disclosed for enabling the initial acquisition of a received coded signal in a direct sequence spread spectrum system using multiple access codes for code division multiplexing. In order to obtain code synchronization by initial acquisition, correlation of a received code with a reference code is performed by an adaptive serial search over the code phase uncertainty which compares the measured signal correlation levels with two thresholds fixed to have a constant difference. During code signal acquisition, the thresholds are increased each time the measured correlation level exceeds the upper threshold, by an amount which equals the difference between the correlation level and the current upper threshold. Initial code signal acquisition is indicated when the detected correlation level raises the threshold levels to a point after which no further correlation measurements exceed the lower threshold. In this manner, false code signal synchronizations normally caused by autocorrelation sidelobes during strong signal reception, are reduced with little degradation in the low signal performance of the system.
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