JPS6464634A - Pulse doppler measuring apparatus - Google Patents

Abstract

PURPOSE:To improve a signal/noise ratio markedly, by receiving the ultrasonic pulse reflected from an object to normalize the phase difference vector thereof and subsequently dividing the angle of the phase difference angle by the transmitting interval of the ultrasonic pulse to calculate frequency variation quantity. CONSTITUTION:A noise suppressing circuit 25 has a function adding and normalizing a phase difference vector according to a tournament system. That is, in the case of N=8, the noise suppressing circuit 25 is constituted of eight adding and normalizing circuits 1-8 of the first stage, four adding and normalizing circuits 9-12 of the second stage for performing the mutual addition and normalization of respective results, two adding and normalizing circuits 13, 14 of the third stage for performing the mutual addition and normalization of respective results and the adding and normalizing circuit 15 of the fourth stage and final output is obtained by finally inputting the outputs of the adding and normalizing circuit 13, 14 to the adding and normalizing circuit 15. As mentioned above, since a noise component can be suppressed to 1/N by adding and normalizing the phase difference vector (2N-1)-times, a signal/noise ratio can be improved in the measurement of Doppler frequency as compared with a conventional one.