| 摘要 |
PURPOSE:To make the discrimination processing simple to simplify the constitution by using a circuit discriminating multiples of 9 in the automatic tuning unit of a synthesizer tuner for medium wave bands. CONSTITUTION:Broadcasting signal radio waves are demodulated to audio signals by antenna ANT, high-frequency amplifier part RF, mixer MIX, intermediate-frequency amplifier part IF and detector part DET. The synthesizer part uses phase synchronizing loop PLL consisting of reference oscillator OSC, programmable frequency divider PD, phase comparator phi/D, low-pass filter LPF and voltage control oscillator VCO. The automatic tuning part gives a start signal to control part CONT controlling up/down-counter U/D-C which gives receiving frequency setting data for programmable frequency divider RD, thereby staring automatic scanning. The discrimination processing is performed by circuit 9n-DET discriminating multiples of 9 connected to display part DISP. |
