The invention discloses a balance-type
branch line coupler with a filter function and solves the technical problem that a
branch line coupler in the prior art cannot inhibit
environmental noise well, does not has functions of power distribution and filter of differential signals and is inconvenient for being connected with a differential device due to the fact that only one end is designed on the
branch line coupler. The balance-type
branch line coupler comprises four resonators (10, 20, 30 and 40) and two
coupling microstrip lines (50 and 60), positive and negative
signal transmission ends of each of the first and third resonators (10 and 30) are connected with positive and negative
signal transmission lines of the first
coupling microstrip line (5), positive and negative
signal transmission ends of the first and second resonators (10 and 20), positive and negative signal transmission ends of each of the second and fourth resonators (20 and 40) are connected with positive and negative signal transmission lines of the second
coupling microstrip line (6), and the positive and negative signal transmission ends of the third and fourth resonators (30 and 40) are communicated. The balance-type
branch line coupler has the
advantage that power distribution, filter and common-mode signal suppression of the differential signals are realized.