A Novel Dual-Frequency Phase Control Network for Reconfigurable Dual-Band Filters and Diplexers With Independent Control of Insertion Phase and Center Frequency

A novel dual-frequency phase control network (PCN) is proposed for the flexible design of reconfigurable dual-band filters and diplexers with independent, continuous phase shift and frequency control. The dual-frequency PCN consists of a dual-frequency resonator for independent frequency control of both bands, a dual-frequency external coupling circuit, and a parallel-to-ground admittance circuit for separate control of admittance. By tuning these components, the network enables a 90° phase shift at each frequency band while maintaining a consistent amplitude response across both passbands. To validate this approach, a reconfigurable dual-band filter in conjunction with the coupled-resonator topology with the proposed dual-frequency PCN was designed, achieving a continuous 340° phase shift in each band. In addition, a reconfigurable diplexer was designed, fabricated, and measured, integrating a common resonator topology with two dual-frequency PCNs, resulting in a continuous 360° phase shift for both bands. Experimental results from both prototypes confirm the effectiveness of the dual-frequency PCN, supported by a detailed theoretical analysis. This design demonstrates significant potential for compact, multifunctional, and integrated devices in frequency division duplex (FDD) and multiband time division duplex (TDD) systems.