| 摘要 |
PURPOSE:To reject multipath interference, by providing a filter which can attenuate the frequency component to be demodulated between a frequency discriminator and a local oscillator and performing frequency modulation with the output to the local oscillator. CONSTITUTION:A reception signal inputted from an antenna P is amplified at a high-frequency amplifier 1 and converted into an intermediate frequency at a mixer 2. This converted signal is applied to an intermediate frequency amplifier 3 for band amplification, demodulated at a frequency discriminator 4 and outputted from a speaker S after being amplified at a low-frequency amplifier 5. On the other hand, a voice signal outputted from the frequency discriminator 4 is inputted to a filter 6 and only an unnecessary band passes through by attenuating a desired demodulation frequency band. Frequency modulation is made for a local oscillator 7 with this signal to avoid the modulated component due to noise in the outside of the desired demodulation frequency band produced with multipath in the output of the mixer 2. |
