| 摘要 |
PURPOSE:To achieve a device which has sufficient attenuation even to an image frequency, by making unnecessary a band pass filter which is expensive and of large size, through the provision of the 1st and 2nd modulators and a BPF which rejects the image frequency component and picks up desired frequency components only. CONSTITUTION:The output of a frequency signal generator 22 is in FM modulation with the output of the 1st local oscillator 4 at the 1st modulator 21, this output signal A and a reception signal are mixed 3 to be the 1st ID signal B and applied to a BPF5. On the other hand, the output of a generator 22 FM-modulates the output of the 2nd local oscillator 7 at the 2nd modulator 23, this output signal D and an output C of th BPF5 are mixed 6 to be the 2nd IF signal E. An unnecessary image signal is removed from a signal E at a BPF24, HPF8 and detector 10, it is low-frequency-amplified at 11 to obtain a demodulation signal. |
