Improved design for symmetrical six-port microstrip coupler (based on double-ring-with-star topology)

Matched symmetrical six-port microstrip coupler

“…The first-order eigenmode model employed in [4] has to be expanded in order to take into account the additional features incorporated into the improved design depicted in Fig. 1.…”

“…Among the various microstrip designs reported in the literature for this coupler, the prototype which achieved the best performance thus far is based on the design proposed by Yeo et al [4] but their coupler only yields a (measured) bandwidth of 25%. We shall utilize [4] as our reference.…”

“…1 depicts the coupler structure we finally obtained. This complicated structure combines the double-ring topology adopted by Kim et al [6], the central star proposed by Judah et al [3], the / 6 π angular displacement introduced by Yeo et al [4] for the six ring-to-ring links, and the tapered lines employed for impedance matching.…”

Six-port precision directional coupler

“…This design is based on edge-coupled striplines which have varied little since their conception and characterisation [1,2]. Since then other coupler configurations have been proposed [3,4] which do not address the issue of attaining high phase and amplitude balance. Recent work by Kother et al addresses phase and amplitude balance in planar, passive dividers [5].…”

“…This design is based on edge-coupled striplines which have varied little since their conception and characterisation [1,2]. Since then other coupler configurations have been proposed [3,4] …”