| 摘要 |
PURPOSE:To provide a AGC circuit whose gain is unchanged when no correlation is detected in the case that the signal of a high level is given to a spread spectrum modulation signal demodulator. CONSTITUTION:A PSK signal demodulator having an RF stage AGC amplifier 1 amplifying a received PSK signal, a mixer 2 converting a the output of the RF stage AGC amplifier 1 into an IF signal, an IF stage AGC amplifier 3 amplifying the output of the mixer 2, a SAW matched filter 5 detecting the correlation of IF signals, a delay detection circuit 6 delaying and detecting a high frequency component from a signal subject to delay detection and a low pass filter 8 eliminating a high frequency component from the signal subjected to delay detection, is provided with an absolute value circuit 9 receiving a signal from the low pass filter 8 to extract an absolute value, a peak detector 10 detecting a peak level of the signal received from the absolute value circuit 9, a peak detector 10 detecting a peak level of the signal received from the absolute value circuit 9, a voltage comparator 11 comparing the output of the peak detector 10 with a reference voltage, and a voltage level converter 12 converting the compared output into a required voltage level. |
