volume | PIER Journals

Abstract

This paper proposes a novel miniaturized interdigital capacitor loaded interdigital filter, which is applied in C-band (3.2 GHz~4.2 GHz). By loading an interdigital capacitor on the open end of the resonator of the interdigital filter, the length of the resonator is shortened by 28%. The resonant frequency offset caused by tap introduction is adjusted by using the method of impedance compensation at the open end of resonator 1 and resonator 5, which further reduces the size of the filter. The miniaturized filter is fabricated on a 0.254 mm-thickness alumina substrate with relative dielectric constant of 9.8 by thin film process. Measured results are as follows: the passband of the filter is 3.2 GHz~4.2 GHz; the insertion at center frequency is -1 dB; the return loss is less than -18.3 dB. The size of the filter is 4.98 mm*6.45 mm (0.15λ_g*0.20λ_g), which is 37.8% smaller than that of the traditional interdigital filter.

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Dr. Luyao Tang

Dr. Xiaoli Jiang

Dr. Hao Wei

Dr. Weiwei Liu

Dr. Wei Han