SPECTRUM SPREAD COMMUNICATION RECEIVING SYSTEM

摘要

PROBLEM TO BE SOLVED: To establish synchronism with a transmission side by compensating characteristic variation of a voltage-controlled oscillator due to temperature variation with simple constitution.

SOLUTION: A multiplier 74 generates an autocorrelation function between a transmission-side spread signal TO and a reception-side spread signal TO' included in a receive signal and smoothes it to generate a gain control signal G for an AGC circuit 78. A synchronism decision circuit 100 decides an asynchronous state when the signal G is less than a threshold and a synchronism compensating circuit 46 generates a staircase voltage signal with time. This staircase waveform voltage is put together with a phase error voltage signal E from a reception synchronizing circuit 44 to generate a control voltage for a VCO 70 generating a reception-side chip clock. As the staircase waveform increases, the frequency of the VCO 70 is swept to acquire synchronism.

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