PURPOSE: To reduce the noise figure by providing a 3dB hybrid coupler whose 1st terminal receives an antenna reception signal, whose 2nd terminal is terminated by a resistor and whose 3rd and 4th terminals connect respectively to an input matching circuit with an equal input impedance to take noise matching.

CONSTITUTION: An input terminal 1 receiving a radio wave received by a microwave reception antenna of a low noise amplifier connects to the 1st terminal 2a of a 3dB hybrid coupler 2 comprising a microstrip line and the 2nd terminal 2b is connected to a resistor 3 for termination. Each signal amplified respectively by field effect transistors 6, 7 is fed to output matching circuits 12, 13 for output impedance matching, the output impedance is matched to 50ohms and the signal is inputted to the 1st terminal 14a and the 2nd terminal 14b of the 3dB hybrid coupler 14. Then two signals are combined by the 3dB hybrid coupler 14 and outputted from an output terminal 16.