MICROWAVE MIXER CIRCUIT AND DOWN-CONVERTER

PROBLEM TO BE SOLVED: To provide a small-sized microwave mixer circuit that selects a signal being a reception object from plural microwave signal inputs and converts the selected signal into an intermediate frequency signal. SOLUTION: A microwave signal at 12GHz band received by a microwave signal input section 2 receives a bias voltage from a comparator 20 via a bias terminal 11 and frequency-converted by a FET 9 receiving a bias current from a bias terminal 23, but the microwave signal received by a microwave signal input section 1 is not subject to nonlinear operation because no bias current is fed to a FET 8 and not frequency-converted, then only an intermediate frequency signal at a 1GHz band corresponding to the microwave signal input section 2 appears at an intermediate frequency signal output section 21.