AUTOMATIC GAIN CONTROL APPARATUS OF HIGH FREQUENCY RECEIVER HAVING IMPROVED RECEIVING SENSIBILITY

摘要

PURPOSE: An automatic gain control apparatus of a high frequency receiver having an improved receiving sensibility is provided to increase a receiving sensibility by stopping an automatic gain control when an input level of a receiving signal is below a reference level and implementing a constant output level by performing an automatic gain control when an input level of a receiving signal is above a reference level. CONSTITUTION: A high frequency amplifier(10) amplifies a high frequency signal from an antenna to a certain level. A high frequency filter(20) filters an unnecessary signal from the signal amplified by the high frequency amplifier(10). A local oscillator(40) outputs a local oscillation signal of a certain frequency. A mixer(30) mixes a local oscillation signal from the local oscillator(40) and a filtered receiving signal and outputs a signal of a frequency signal. A demodulator(50) receives a signal from the mixer(30) and demodulates into a certain signal. An automatic gain controller(70) detects an output signal level of the signal from the demodulator(50) and outputs an automatic gain control signal to the high frequency amplifier(10) for adjusting the input level of the receiving signal based on the detected output signal level.