LAUSR

We propose a novel, eight-port, forward-wave directional coupler with periodically patterned ground structures. The input impedances of the four modes for the proposed coupler can be matched, and the phase difference between the even–even and the other three modes is also strongly enhanced. Equivalent models have been constructed to predict the propagation properties based on the Bloch–Floquet theorem. A design procedure is also proposed completely based on the equivalent models. The proposed couplers, with both equal and unequal power divisions, are fabricated on a Duroid substrate. Then, there is good agreement between theoretical simulations and measurements.