| 摘要 |
PURPOSE:To make it possible to obtain doppler frequency corresponding to a given frequency, without improving the measuring accuracy and modifying circuit of doppler extracting section, by making it possible to vary doppler bias frequency appropriately. CONSTITUTION:A signal of fb+fd extracted from a signal-receiving device and a synthesizer output signal fo are put through a mixer 11 to obtain a differential signal component (fb-fo)+fd, and frequency of this signal is measured by a reciprocounter 12 and thus obtained data are processed by a microcomputer 13, and at the same time, a frequency of fb-fo is appropriately selected by controlling a frequency synthesizer 10. It is possible, by employing such a mechanism, to change bias frequency in the direction of minimization of the doppler frequency error and the quantization error. In other words, the doppler measurement in the counter 12 is a periodical measurement of counting N cycle of an input signal by a clock frequency, and as a bias frequency and a counter resolution are correlative with each other, it is possible to improve measuring accuracy of distance changing rate by lowering the bias frequency. |
