PURPOSE: To make a mixer small-size and improve characteristic with changing the image state of each mixer diode and facilitating the adjustment of a conversion loss and a noise factor by changing the length of a terminating short-circuit slot line which is provided at the middle between image recovery mixers.

CONSTITUTION: Terminating short-circuit slot line 15 is arranged in the conversion part of micro strip line 1, which is provided at the middle between balanced mixers 3 and 4, and slot line 2, and image signals generated from mixers are synthesized and are propagated to line 15 and are reflected in an opposite phase by short- circuit end 16 and are distributed to slot line 2 at point A. As a result, the image state can be changed by changing the length of line 15.