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.
Highlights
Quadrature coupler and rat-race coupler are essential components and have been widely used in microwave circuits and systems [1]–[4]
In [16], rat-race or branch-line coupler was demonstrated in one single unit by electrically switching, the capability of frequency agility is not provided
Each EVA cavity resonator is constructed by an inner capacitive post and a circular outer via-wall
Summary
Quadrature coupler and rat-race coupler are essential components and have been widely used in microwave circuits and systems [1]–[4]. In [27], a reconfigurable filter with rat-race coupler and quadrature coupler functions has been proposed, good performance has been obtained. 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, single-ended two-pole, three-pole, and four-pole filters, in addition to continuously frequency, independent bandwidth, and power-division tuning. DESIGN Fig. 1(a) shows the 3-D view of the proposed multi-functional four-port coupler It is fabricated using conventional single-layer printed-circuit and consists of four (evanescentmode) EVA cavity resonators. The proposed four-port coupler structure can work under different function modes by reconfiguring the coupling coefficients between adjacent resonators. These function modes include the filtering quadrature coupler mode, filtering ratrace coupler mode and the multi-pole bandpass filtering mode, which will be discussed below in details
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