| 摘要 |
PURPOSE:To prevent a transmitted output from turning around to a receiver, and to supply received electric power to the receiver efficiently, by using a directional coupler as the antenna coupling circuit of a radio transmitter and receiver which uses a transmission and reception common-use antenna. CONSTITUTION:A main transmission line 34 and a subordinate transmission line 35 are coupled together, and a directional coupler 30 terminating one terminal of the subordinate transmission line by a dummy load 36 is used as an antenna coupler. Then, received power induced at an antenna 11 is supplied nearly as it is to a receiver 13, and the output of a transmitter 12 is attenuated and outputted to a terminal 31, but scarcely supplied to a terminal 32. Namely, although the transmitter and receiver are connected in parallel, the sensitivity of the receiver is not spoiled and the transmitter output never turns around to the receiver, so the sensitivity of the receiver is never decreased, so that the reliability and performance of the transmitter and receiver are improved. |
