RADIO SIGNAL RECEIVING SYSTEM

摘要

PURPOSE:To detect the presence of an electromagnetic wave such as an X band radar signal or K band radar signal by inserting a key signal like a pilot signal to an antenna output, and using only a signal including the key signal as the detecting signal. CONSTITUTION:A signal of the X band antenna 10 is coupled to a mixer 14 and heterodyned with a signal from a local oscillator 16 and frequency-modulated by the pilot signal. The output of the mixer 14 is fed to a common amplifier 20 via an IF amplifier 18. A K band antenna 12, mixer 22, local oscillator 24, and an IF amplifier 26 are constituted similarly. The output of the common amplifier 20 is connected to a mixer 28 receiving a signal from a local oscillator 36. The output of a band pass filter 34 is amplified by a tuning amplifier 36 and fed to a discriminator 38. The intermittent pilot signal demodulated by the discriminator 38 passes through a narrow band pass filter 40 and is given to a PLL42 via the amplifier 41.