| 摘要 |
PURPOSE:To decrease the number of parts, by using the output of an oscillator for local oscillation comparison and calibration of a synthesizer tuner as the output of the 2nd local oscillator. CONSTITUTION:An input signal from an antenna 1 is converted into a 10.7MHz intermediate frequency through a mixer 4 which mixes the local oscillation frequencies from a high frequency amplifier 2 and a voltage-controlled oscillator 3. The local frequency of the oscillator 3 and the tuning frequency of the amplifier 2 are controlled by the output of a phase comparator 14 which compares the local oscillation frequency with the signal obtained by frequency-dividing the frequency division output of a programmable frequency divider 13 by the output of a crystal oscillator 22 for local oscillation comparison and calibration through a frequency divider 12. The output of the crystal oscillator 22 is used even as the 2nd local oscillation signal, and a mixer 7 uses said signal to apply a signal of said intermediate frequency to an FM detector 8 as a signal of the 2nd intermediate frequency, i.e. 2.15MHz. Successive signal demodulation is carried on by the circuit in the figure as usual. |
