| 摘要 |
PURPOSE:To remove a transmission blind zone by adding ODT transmission (Omnidirectional Transmission)/RDT transmission (Rotational Directional Trans mission) changeover control circuit. CONSTITUTION:An instrument having a transmitter and receiver group 1, a power amplifier circuit 2, a changeover circuit 3, a transmission phasing circuit 4 and an oscillator circuit 5 is added with an RDT/ODT changeover control circuit 7. The circuit 7 outputs ODT transmission control pulse to the circuit 3 after the RDT transmissions of i-times, which are followed by ODT transmission. When a target is present within a range R/2 in a bearing theta, although target reflecting wave by RDT transmission pulse can not be received because it arrives within transmitting period, sound wave by the succeeding ODT transmission is transmitted and the whole transmission has been completed at a time when the reflection of the sound wave arrives, so that reception is possible whereby the transmission blind zone of a short range can be removed.
|
