| 摘要 |
PURPOSE:To prevent mis-synchronization even when a large disturbing wave is received by comparing an automatic gain control voltage level of each amplifier at high and intermediate frequencies and controlling the operation of a synchronous controller in response to the compared output. CONSTITUTION:An input signal from an antenna is amplified by an automatic gain control high-frequency amplifier 2 and inputted to a mixer 4. A local oscillator 3 generates a hopping output and inputs it to a mixer 4 at a frequency apart by an intermediate frequency from the antenna input signal by using a digital output from a hopping pattern generator 5. The generator 5 is actuated by an output of a lead phase clock generator 6 when the operating clock is not synchronized and actuated with a subsequent clock generator 7 when synchronized. An output of the mixer 4 is inputted to an intermediate frequency amplifier 9 through a BPF8. When a strong disturbing wave is inputted to an antenna, the input to the amplifier 2 is large and the input to the amplifier 9 is small, then the AGC voltage of both the amplifiers is compared (12), the comparison output holds the state of a synchronizing discriminator to prevent mis-synchronism by the disturbing wave. |
