A Coupling-Path Reconfigurable Quadrature Coupler With Wide Range of Tunable Frequencies and Power Division Ratios

In this article, a coupling-path reconfigurable quadrature coupler is proposed with a wide tuning range of frequencies and power division ratios, which consists of three pairs of varactors and eight transmission lines. By analyzing the admittance matrices of the proposed coupler, the constraint conditions for both forward coupling (FWCP) and backward coupling (BWCP) can be established. Then, through selecting suitable circuit parameters (characteristic impedances, lumped elements, varactors, and so on), a wide range of tunable frequencies and power division ratios can be realized for both FWCP and BWCP paths, respectively. Finally, a prototype is fabricated and measured for verification. The measured results show that the proposed coupler can realize a wide tuning range of frequencies from 0.8 to 1.5 GHz (0.9–1.5 GHz), and a large tuning range of the power division ratios from −10.2 to −0.7 dB (−20.3 to 19.3 dB) in the FWCP (BWCP) path. Excellent agreement is obtained among the results of circuit simulation, electromagnetic (EM) simulation, and measurement, it not only demonstrates that the proposed quadrature coupler features a simple topology, reconfigurable coupling path, and wide tuning range of frequencies and power division ratios, but also confirms the effectiveness of the applied constraint conditions.