Miniaturized Suspended-Substrate Two-Conductors Resonator and a Filter on Its Base

The paper is devoted to an investigation of two-conductor suspended-substrate resonators. For the purpose of miniaturization conductors of a resonator are folded. Four types of the resonator differing in conductors’ configurations were considered. Their Q0-factors and resonant frequencies were studied. Based on results of the study two types of the resonator appeared unsuitable for an application in compact filters. Two other types were investigated in concern of their interaction: dependencies of coupling coefficients versus space between resonators and versus distance from substrate’s surfaces, and package’s covers were obtained. Based on the dependences a type of the resonator suitable for designing compact BPF was chosen. A four-pole BPF was simulated and fabricated. Good agreement between simulated and experimental results is observed. The main filter’s characteristics are the next: substrate has ε = 80, thickness 0.5mm, lateral sizes 0.13λg ×0.09λg (18.7mm×13.2 mm). The central frequency is 305 MHz; bandwidth is 39 MHz; passband minimum insertion loss is 2.0 dB; passband return loss is less −14.6dB; −40 dB stopband width is 480MH