| 摘要 |
PURPOSE:To improve the performance of reception, by using a common gate circuit for a high frequency amplifier at the reception side and obtaining the isolation between the input and output. CONSTITUTION:At the transmission, by an antenna relay 1 is selected as shown in a figure, and an output of a power amplifier 4 is emitted from the antenna. A reception switching relay 2 is operated via a transmission power supply TXVcc and a diode D3 and selected to the opposite position as shown in the figure. In this case, a reception high frequency amplifier 3 comprising FETs is biased for the gate G to -Vcc to isolate terminals (f) and (g). Thus, the power amplifier 4 is not subjected to a failure such as oscillation by feeding back the output to the input via a stray capacitance with the reception circuit. At the reception, the relay 1 is selected to the position (b), and the relay 2 selects a through-circuit 7 and the high-frequency amplifier 3 with a switch 9. The insertion of diodes used in conventional technology is not required for the input and output of the amplifier 3, thus improving the performance of reception of the receiver. |
