A Broadband 3 dB Coplanar Waveguides Directional Coupler with Conductor-backed Asymmetric Coplanar Waveguides Compensation

Abstract

A novel broadband 3 dB directional coupler using broadside-coupled coplanar waveguides and conductor-backed asymmetric coplanar waveguides (ACPW) is proposed. To broaden the bandwidth (isolation more than 20 dB), a conductor-backed ACPW is inserted to each port of the proposed coupler as the parallel compensation capacitance. The proposed coupler can be easily realized on a single-layer substrate by using general PCB processes. The proposed coupler exhibits good impedance match , high isolation , balanced power distribution (3.2±0.4 dB), and consistent 90° (±0.6°) output ports phase difference across a significantly broad bandwidth of 50.6%, from 1.04 to 1.80 GHz. Simulation results are compared with the measurements, and a good agreement is observed.