Vol. 109

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A Novel Miniaturized Capacitor Loaded Interdigital Filter

By Luyao Tang, Xiaoli Jiang, Hao Wei, Weiwei Liu, and Wei Han
Progress In Electromagnetics Research M, Vol. 109, 39-49, 2022


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 (0.15λg*0.20λg), which is 37.8% smaller than that of the traditional interdigital filter.


Luyao Tang, Xiaoli Jiang, Hao Wei, Weiwei Liu, and Wei Han, "A Novel Miniaturized Capacitor Loaded Interdigital Filter," Progress In Electromagnetics Research M, Vol. 109, 39-49, 2022.


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