| 摘要 |
PURPOSE:To always hold the distance resolution and the sensitivity constant irrespective of a long distance and a short distance by constituting the frequency generating means of a variable frequency generating means for generating a continuous variable frequency signal by which its frequency is varied in accordance with a receiving time as time elapses. CONSTITUTION:A VCO(voltage control oscillator) 40 outputs a signal of a frequency f5 against a received echo signal from a short distance as shown by a full line (b), and a multiplier 5 multiplies both the signals and as its output signal, signals of a sum component and a difference component centering around the frequency f5 as shown by full lines (c), (d) are obtained. On the other hand, as for a received echo signal from a long distance, a signal of a frequency f7(f7=f5+DELTAf''') is outputted as shown by a full line (h), and by the multiplier 5, signals of a difference component and a sum component centering around the frequency f7 as shown by full lines (i), (j) are obtained. When this signal is inputted, a band pass filter 7 outputs a signal having a frequency band of (f6+ or -DELTAf'') being the same as the case of a short distance. This signal is inputted to an orthogonal detecting part 8, and becomes a complex signal contained in a frequency band DELTAf'' as shown by a full line (s), and the same frequency band as the received echo signal from a short distance can be secured. |
