| 摘要 |
PURPOSE:To provide sonar detected images of high resolution free from any time delay without increasing the size of an electro-acoustic transducer by subjecting the receiving signals of two systems to specified processing thereby making frequency multiplication. CONSTITUTION:The reflected ultrasonic waves of pulse-modulated linear frequency modulating ultrasonic waves from the target are received in the two systems R, L of an electro-acoustic transducer 1. The L-system received signal is mixed with the signal of a frequency twice higher than the central frequency of the transmission waves in a mixer 5 and goes through an LPF 16 to become the lower side-band which is then multiplied by the R-system receiving signal in a multiplier 11. When the upper side-band being the output signal of the circuit 11 is drawn out with a BFP 12 is subjected to the mixing similar to that of the mixer 5 with a mixer 13 and is made to a lower side-band with an LPF 14, then it becomes the signal corresponding to the target distance of a high bearing resolution of the frequency proportional to the delay time of the receiving signals of both systems R, L in correspondence to the target bearing. When this signal is frequency-multiplied with a frequency multiplying circuit 15 which compresses time axis and is then applied to a frequency analysis circuit 16, the signals are processed without time delay. |
