A Wideband Planar Hybrid Coupler Using Coupled-Line Power Divider and Broadband Phase Shifter

A wideband planar hybrid coupler with an 82% bandwidth is proposed in this paper. The proposed hybrid coupler consists of a wideband two-section coupled-line power divider and a broadband 90 degrees phase shifter. The two-section coupled lines, where, not only perform impedance matching, but also make the total circuit of this divider compact. The broadband shifter employs a pair of open- and short-circuit stubs inserted onto the reference transmission line to compensate the phase variation of a conventional transmission line which is in proportion to the operating frequency. Therefore, wideband impedance matching is achieved and the bandwidth of phase shifting is broadened. Thus, a wideband 90 degrees hybrid coupler with good performance both on power dividing and quadrature phase shifting is accomplished. To prove the design methodology, a hybrid coupler operating at 3.0 GHz is designed and the simulation is accomplished with ANSYS HFSS 14.0. Across the frequency bandwidth for reflection coefficient no more than -15dB, the maximum amplitude unbalance is 0.3dB, the phase variation is +/- 5 degrees, and the port isolation is better than 20 dB.