On the Design of a New 4x4 Coupler for C Band based on a 180° Coupler at Microstrip Technology

In this paper, a new design for a 180 hybrid directional coupler is presented and implemented, the coupler works in the frequency range of the C band spectrum from 5.9 to 6.1 GHz in UP-LINK mode. The designed coupler achieves less weight, use less coupler sections, reaches phase difference in the output ports and its able to handle larger bandwidths. First, a study of the state of the art about this type of couplers, their mathematical analysis, and the methods to be used, are reviewed together with the initial design of a 180 hybrid coupler section. Then, the electromagnetic behavior of this hybrid ring, as well as its coupling to the host transmission line, are studied, and analytical equivalent-circuit models are also proposed. A new multiple sections coupler with 4 input and 4 output ports, was then generated from this initial hybrid ring design, with the aim of increasing the bandwidth. A final directional coupler implementation was then fabricated using Microstrip technology for its subsequent analysis at 6 GHz. Both simulation and experimental results show good performance agreement. A 16.67% bandwidth was achieved.