A new type of planar 180 degrees hybrid using intentional impedance mismatch for improved bandwidth and arbitrary power division ratio

Abstract

A wideband planar 180 hybrid is proposed for arbitrary power division ratios and implementing cascaded planar structure. In addition, the proposed structure not only has the same function as the conventional ring hybrid, but also has a planar cascade connection when connecting other components because the output ports have same direction. The proposed planar 180 hybrid consists of two 3 dB couplers, and 4 transmission lines (TLs) with symmetrical TLs connected in series with different impedances of ZA and ZB. The design theory of the proposed structure is based on a cascaded multiport connection form, converged from transmission matrix to S-parameter, and the ratio of ZA and ZB impedances is derived for wideband performance. The design equations are verified as the measurement results of the magnitude and phase characteristics. The proposed structure, regardless of whether 2 TLs are connected in cascaded form, has a 29% reduced area compared with the conventional ring hybrid.