| 摘要 |
PURPOSE:To perform doppler detection precisely in the case when a receiving signal is discontinued, by outputting the sine wave frequency which is in the immediately previous state. CONSTITUTION:When the receiving signal is normal, a multiplexer 16 is operated by the output of a coincidence detecting circuit 11, the counted value of a difference signal counter 15 is transferred to a register 17. The output signal of said register 17 is converted to an analog signal by an A/D converter 18. Said analog single is supplied to a voltage control oscillator 19. The difference output signal in frequencies which are proportional to the voltages of analog output signal is obtained. When the receiving signal is discontinued, the difference signal is also discontinued, the state of a gate counter 9 and the state of a gate counter 10 are not coincided, and the multiplexer 16 does not operate. Therefore, the contents of the register 17 are held at the immediately previous state before discontinuance, and the output of the voltage control oscillator 19 remains at the frequency immediately before the receiving signal is discontinued. |
