Compact Phase-Reconfigurable Couplers with Wide Tuning Range

To meet the stringent requirements of the emerging wireless communication system, the components should exhibit high flexibility in the control of operating frequency, amplitude characteristics, and also phase characteristics. Among them, the reconfigurability in phase is important but difficult to implement. The existing phase-reconfigurable coupler can only provide a tuning range between 45° and 135°, resulting in limited applications. To solve this problem, a tunable unit consisting of open and shorted stubs and tunable capacitors is introduced between two eighth wavelength coupled lines to construct a compact phase-tunable coupler. For the first time, the continuous tuning range of a phase-reconfigurable coupler is extended to 0°-180°. The corresponding theoretical analysis has been conducted. For the demonstration, two couplers operating at 2.4 GHz were fabricated and measured. Good agreement between simulation and measurement can be observed. Coupler I achieved a phase tuning range from 45° to 135°, maintaining equal power division characteristics. The amplitude bandwidth defined by 10-dB return loss and 1-dB amplitude imbalance was larger than 16.3% for all states. Coupler II provided a tunable phase from 0° to 180° over an amplitude bandwidth larger than 12.5%. These results validate the effectiveness of the proposed structures.