| 摘要 |
PURPOSE:To reduce sharply the consumption of a transmission power and to improve a tracking time or a detecting distance to a large extent, by conducting first tracking in a wide range while receiving an echo of a target generated by a first transmission signal having low frequency being nondirectional, and by continuing the tracking with a second transmission signal switched which is a pulse-modulated wave having a narrow-angle directivity and high frequency when an underwater projectile is steered reversely beyond the direction of the target. CONSTITUTION:A low-frequency pulse-modulated wave of about 5kHz is used as a first pulse- modulated wave signal 401. Since a transmitter 1 receiving the above wave as an input has the non-directional transmission directivity characteristic, a reflected echo is easily caught and received by receivers 3A and 3B, and 3C and 3D owing to the non-directivity of a transmitted sound wave. When an underwater projectile 11 goes beyond the direction of a target 0, so as to be opposed face-to-face thereto with the output characteristic of the receivers 3A and 3B being reversed, a reverse steering detecting means actuates to switch the output of a transmission circuit to a second pulse-modulated wave signal 402, i.e. a pulse-modulated wave signal having a frequency several times higher than that of the first pulse-modulated wave signal 401, so as to increase the number of waves of the echo. Furthermore, this echo is delivered as a transmission sound wave having a narrow beam from a transmitter 2 having a narrow- angle transmission directivity to continue tracking. |
