| 摘要 |
PURPOSE:To obtain an inexpensive, reliable receiver by setting the frequency division ratio of the PLL circuit for channel frequency selection of an FM preset receiver by a diode matrix circuit. CONSTITUTION:In the FM preset receiver of a radio common system, an FM- modulated signal is applied to a terminal 20 through a coaxial cable and a branching device and then processed by frequency conversion 23 to make a speaker 34 sound through an intermediate frequency amplifier, a detector and an audio amplifier. A local oscillating circuit consists of a voltage-controlled oscillator 24, a tuning circuit 25, a prescaler 26, a PLL circuit 27, and a filter 28. The circuit 27 has bit terminals A-H for determining the frequency division ratio of the input signal, and the output of a matrix circuit 29 varied with a channel changeover switch 30 is inputted to the terminals A-H. For example, when the switch 30 is placed at a terminal (a), the circuit 29 outputs 10100100 to set the frequency division ratio of the circuit 27 to 164. By changing over the switch 30, the reception frequency of a prescribed channel can be selected. |
