| 摘要 |
An improved sequential threshold detection circuit for use in the receiver of a spread-spectrum communication system is disclosed wherein the improvement resides in the employment of a feedback circuit for maintaining a pre-selected constant median dismissal time. In the preferred embodiment the feedback circuit comprises a flip-flop (70), a very long time constant integrator (72), and a one-shot (74) connected between a comparator (64) and a summing amplifier (60) for varying a threshold bias voltage applied to the summing amplifier. In an alternative embodiment, the feedback circuit serves to selectively vary the gain of a variable gain amplifier (110) in such a manner to vary the individual trial and error dismissal times to provide a substantially constant median dismissal time over the entire detection process. The detection circuit of the invention provides a signal indicating whether the pseudo-random noise generator (26) in the system receiver (9) has been synchronized to the pseudo-random noise generator (16) in the system transmitter (8), but does so with improved reliability, accuracy and statistical performance with reduced manufacturing cost.
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