No abstract

A novel evanescent-mode cavity filter with multiple reconfigurable functions including filtering rat-race coupler, filtering quadrature coupler and multi-pole filtering is proposed in this paper. It simply consists of four substrate integrated waveguide (SIW) evanescent-mode cavity resonators which are arranged in a ring loop. By loading piezoelectric actuators on top of each resonator and inserting varactors between adjacent resonators, the structure can achieve multiple reconfigurable functions among filtering rat-race coupler, filtering quadrature coupler and single-ended multi-pole filters, in addition to continuously frequency, independent bandwidth, and power-division tuning. Measurement shows that the filtering quadrature coupler corves a frequency range of 2.08-3.00 GHz with insertion loss of 2.99 ± 0.31dB, while the filtering rat-race coupler corves a frequency range of 2.31-2.71 GHz with insertion loss of 2.97 ± 0.13dB; The single-ended filter can be switched among two-pole, three-pole, and four-pole with frequency range of 2.38 to 3.01 GHz, 2.47 to 3.08 GHz and 2.53 to 3.00 GHz, respectively. Good agreement is obtained between simulated and measured results. INDEX TERMS Evanescent-mode cavity, quadrature coupler, rat-race coupler, reconfigurable filters. FIGURE 1. Structure of the proposed multifunction filtering coupler. (a) 3D-view. (b) Top view.

In this paper, a trisection filter with reconfigurable transmission zeros based on the evanescent‐mode cavity (EVA) resonators is proposed. The design incorporates three EVA resonators. The varactors are set between two EVA resonators. By controlling the varactor capacitance value, couplings can be switched between electrical coupling and magnetic coupling. Based on this technique, the resulting two zeros can be designed to the desired position. Furthermore, a novel method by analyzing the magnitude and phase of trisection filters is proposed. Using this method, the transmission zeros position can be determined quickly. Measurement shows that the filter covers a frequency range of 2.11–2.83 GHz. Two transmission zeros can be arbitrarily designed to the left or right sides of the passband. Good agreement is obtained between simulated and measured results.