| 摘要 |
PROBLEM TO BE SOLVED: To provide a low-noise amplifier circuit in which the deterioration of NF is suppressed in the ordinary state of propagating signals through a path on the side of an amplifier while being provided with a bypass circuit and a switch for switching the bypass circuit. SOLUTION: First and second unit amplifiers A1, A2 are connected between first and third 3dB directional couplers H1, H2, and a switch SW1 is provided to switch whether an output signal from the fourth port (4) of the first 3dB directional coupler H1 is to be propagated to a reflection-free terminator T1 or to be propagated to a bypass circuit S. In the ordinary state, a signal from the first port (1) of the second 3dB directional coupler H2 is outputted from an output part OUT1 but when changing over the switch SW1, the signal is outputted from an output part OUT2 via the bypass circuit S, and no switch is present on the path via the amplifiers A1, A2 thereby obtaining excellent NF characteristics. COPYRIGHT: (C)2005,JPO&NCIPI
|
