| 摘要 |
PURPOSE:To facilitate the detection of a target and the measurement of distance in the direction of main beam even when gain difference is small between the main beam and side lobe by suppressing a received signal in the side lobe. CONSTITUTION:As a gate 13 is opened only when counts of a No. of cycle difference counter 6 are zero, no signal appears at an output terminal 14 with the number of cycles counted one or more however extremely small the output 151 of a phase difference detector 5 may be. The phase detector 5 judges that the phase difference is zero if the phase difference from input signals 141 and 142 is an integral factor of 2pi. So, the detection of the phase difference 0 or the proximity thereof with the phase detector 5 always does not shows that the sound wave involved comes from the direction of main beam. In this respect, a counter 6 is provided to identify sound waves in the direction other than the main beam. When difference of the number of cycles is one or more from signals 141 and 142, the sound wave involved can be judged to come from the direction other than the main beam even if the phase difference detected by the detector 5 is less than the range of the main beam. |
