Wideband asymmetric coupler with optimally positioned capacitors for improved directivity

The design and simulation of a wideband coupler for improved directivity is investigated. The coupled line coupler is considered for weak (or lose) coupling purposes. An improved bandwidth performance is achieved by increasing the number of stages of the coupled line coupler, thus resulting in a Multi stage coupler. The research focuses on the 3 stage coupler with optimally positioned capacitances, however the result can be easily extrapolated and generalized to any number of stages. An odd number of stages is considered for structural symmetry and wider bandwidth performance. The performance of the conventional multistage coupler, the compensation with a single capacitance, multiple capacitances and optimally positioned capacitances for both symmetric and asymmetric couplers are investigated in detail with special focus on the asymmetric couplers. This dissertation introduces the novel Pointer-Robust optimization scheme for optimal positioning and the asymmetric compensation for enhanced bandwidth-directivity performance. Several design examples and simulation results are presented and the results are confirmed by measurements. The results confirm the novel optimization scheme and compensation approach.