| 摘要 |
PURPOSE:To increase the frequency deviation and to improve the C/N ratio without increasing the multiplying number, by converting once the modulated wave for the frequency into a low frequency. CONSTITUTION:In the FM modulation system of the FM radio reception device, first mixer MIX2, which mixes the modulation signal sent from oscillation modulator OMOD (first oscillator) performing the frequency oscillation and the high frequency output of second oscillator OSC, is installed to convert the modulated wave into a low frequency. This converted mixture signal is applied to multiplier MP1 to be changed to 1/n (n = integer) intermediate frequency of the reception device and then to be converted to the same frequency as the intermediate frequency. Then the signal converted to the same frequency as the intermediate frequency is applied to second mixer MIX3 via crystal filter X-FIL and then mixed with the high frequency output supplied from second oscillator OSC to obtain the necessary output frequency. The band pass filter of intermediate frequency amplifier IA and filter X-FIL are used in common to eliminate the unnecessary waves for the intermediate frequency signal. |
