| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a waveguide type low noise amplifier having a switch for the plane of polarization which has a simple constitution and never generates abnormal oscillation (parasitic vibration). SOLUTION: This low noise amplifier includes a waveguide 11, a pair of input probes 1 and 7 which are partly exposed in the waveguide 11 and arranged to have a 90-degree difference of angle between them, the amplifiers 3 and 5 which are placed outside the waveguide 11, the waveguide/microstrip mode conversion parts 2 and 6 which secure the electrical connection between the amplifiers 3 and 5 and the probes 1 and 7 respectively, and an amplified signal coupling part 4 which is electrically connected in the rear stages of amplifiers 3 and 5 for the coupling of microwaves. In such a constitution, the transmission lines having electrical length of 211 are inserted before and after the amplifier 3 or 5 so as to satisfy the relation of 211=λ(2n+1)π-(A+B)}/(2π) among the wavelengthλof frequency having the gain, the transmission phase A of the amplifier 3 or 5 and the transmission phase B of a circuit passing via the part 4→the amplifier 5→the part 6→the probes 7→1→the part 2 or the part 6→the probes 7→1→the part 2→the amplifier 3→the part 4 excluding the amplifier 3 or 5.</p> |
