Two-Element Retrodirective/Beam-Switching Array Using Dual-Mode Coupler

A simple two-element integrated array, capable of dual-mode operations, is investigated. With the feeding network unchanged, the integrated array is identical to a reflection-type retrodirective array in one band, but automatically reconfigures as a beam-switching array with mutually orthogonal sum and difference patterns in the other band. The core building block is a dual-mode coupler, which functions identically to a 90° hybrid coupler and a 180° hybrid coupler, respectively, in the two bands. By integrating this unusual dual-mode coupler with reflection loads, diplexers, gain stages, and antennas, a planar integrated array is demonstrated on a printed circuit board. The idea is supported by experimental results including S-parameters and radiation patterns.