| 摘要 |
<p>PURPOSE:To achieve lightening and miniaturization of a reception-system protective circuit by a method wherein a PIN diode is installed to be in parallel with the joint of a branch line which is added to the main line of a band rejection filter. CONSTITUTION:In a band rejection filter, a forward current is made to flow to PIN diodes 12a, 12b from a bias terminal 16 in a transmitting operation, the diodes 12a, 12b are set to a short-circuited state, and a transmitting signal which creeps to a main line 9 is cut off. When a reverse voltage is applied to the diodes 12a, 12b from the terminal 16 in a receiving operation, the diodes 12a, 12b are set to an open state, and branch lines 10a, 10b are connected to the line 9 via gold wires 13. When the length of the lines 10a, 10b is selected to be a prescribed value, the lines are set to a passage state with reference to a received signal passing through the line 9 and they are set to a low impedance and a cutoff state with reference to an inessential signal which is different from a transmitting signal by the interference of radio waves. As a result, it is possible to prevent a reception-system amplifier to be connected from being saturated or damaged by the inessential signal.</p> |
