| 摘要 |
The receiver receives a complex spread spectrum signal modulated using complementary code keying. The received signal is down converted and cross correlated with code words using a Fast Walsh Transform. The peak magnitudes resulting from the Fast Walsh Transform are selected for a period before, during, and after an expected symbol boundary. The relative magnitudes of the early, on-time and late measurements are compared to determine which output has the largest magnitude. If the on-time measurement is the largest, symbol tracking continues without a timing adjustment. If the early measurement has the greatest magnitude, then the tracking timing is adjusted one period downward to shorten the period expected before the next symbol boundary. If the late measurement has the largest magnitude, then the tracking timing is increased by one sample period to increase the period expected before the next symbol boundary. This process repeats itself to provide accurate symbol tracking.
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