PURPOSE: To decrease the transmission loss of a microwave by providing a circulator group connected in cascade to an output terminal of a broad band pass filter and a circulator group connected in cascade with other output terminals of the circulator and forming multi-stage for wave branching/ synthesizing constitution being the combination of the circulators and band pass filters.

CONSTITUTION: The broad band pass filter 18 is a broad band pass filter passing waves whose frequencies are f11∼f14, and the attenuation characteristic is shown in broken line 19. Thus, waves made incident in an input terminal A whose frequencies are F11∼f14 and f21∼f24 are branched into the frequencies f11∼f14 and f21∼f24 by the circulator 17 of the broad band pass filter 18. Then each frequency is branched by circulators 1∼4, filters 9∼12, circulators 5∼8 and filters 13∼16. In considering the wave of the frequency f24, the transmission loss is caused by 9 paths comprising the circulators 17 and 5∼8, then the loss is less in comparison with conventional 16 paths' loss.