This paper presents a novel structure for realizing a coupler with controllable power divisions, which is composed by two couplers and two phase shifters cascaded between them. This structure is applicable to constructing couplers with extremely-wide-range tunable power division, and the phase-difference performances can be predicted and controlled flexibly. In this paper, the rigorous design equations and methodologies are exhibited. For verification, two prototypes with rat-race and quadrature operations are fabricated and measured, and the measured results sufficiently confirm this topology to be effective and correct.
