Compact Branch-line Coupler using Radial stubs

Abstract

This manuscript shows a novel compact branch-line coupler with radial stubs installed on each branch. The proposed implementation is only 10 mm by 10 mm and it achieved a size decrease of 70% compared with a traditional one. Measured S11, S21, S31 and S41 of the proposed coupler are better than −23, −3.6, −3.6 and −27 dB at 3 GHz, respectively. Moreover, the phase difference between coupling and through ports is within 0.9°.