A novel wide-band hybrid coupler using coupled-line power divider and improved coupled-line phase shifter

Abstract

A novel hybrid coupler aiming for wide-band applications is proposed in this paper. This hybrid coupler consists of a broadband Wilkinson coupled-line power divider and an improved wide-band coupled-line phase shifter. Taking advantage of the coupled-line section, the power divider achieves both compact circuit configuration and wide-band performance. In lieu of patterned ground plane and lumped capacitors, the coupled-line phase shifter can be constructed on a single-layer printed circuit board for wide-band operation. For this proposed phase shifter, the scattering parameters (S-parameters) expressions are derived and the optimal structural design parameters for achieving zero reflection coefficients are highlighted. After carefully choosing the circuit parameters, a new wide-band hybrid is constructed by combining a power divider and the proposed phase shifter. To verify against the theoretical calculation in terms of S parameters and phase information, a hybrid operating at 3 GHz is designed, simulated, and fabricated through microstrip technology. Close agreement is obtained between simulation and measurement results.