| 摘要 |
PURPOSE:To correctly display the reception signal frequency and to realize low cost constitution, by providing the complement number signal generating circuit. CONSTITUTION:The complement number signal generating circuit 21 is provided at the output side of the synchronous oscillator 19 of superheterodyne system receiver. The circuit 21 is the circuit generating the output signal taking the 10's complement in signal frequency fo of the oscillator 19 as the frequency, and it has the crystal oscillator 22 and consists of the oscillator 23 oscillating the frequency of accurate 1,000kHz, mixing circuit 24 generating the output signal of difference and sum of each signal frequency from the output signal of the oscillator 23 and oscillator 19, and LPF25 transmitting only the component of difference from the output signal of the circuit 24 as the output signal fH. Accordingly, when fo=455kHz, the signal of fH=1,000-455=545kHz is outputted. Further, the output signal fH of the circuit 21 is fed to the up and down counter (count circuit) 27 of the reception frequency display unit A via the OR gates 26, 38. |
