MIM电容器及其在慢波滤波器设计中的应用

MIM capacitor and its application in slow-wave filter design

为提升微波电路的集成度,提出了一种基于印刷电路板(PCB)的金属-绝缘体-金属(MIM)电容器,并将其应用在小型化慢波带通滤波器(BPF)设计中。该MIM电容器由一对刻蚀在基板两侧的正方形贴片组成,容值为5.26 pF,远大于传统的交指电容器的容值。进一步将该MIM电容器嵌入到一个传统的开环谐振器(OLR)内部空间中,形成一个慢波OLR。利用该慢波OLR设计了一种小型化二阶慢波BPF。与加载交指电容器的BPF相比,所提出BPF的尺寸缩减了40%。其阻带插入损耗在大于20 dB的频率范围达到其通带中心频率的4.46倍,表明所提出的BPF具有宽阻带特性。实测和仿真结果吻合较好。

To improve the integration of the microwave circuits,a metal-insulator-metal(MIM)capacitor based on printed circuit board(PCB)was proposed and applied in the design of miniaturized slow-wave bandpass filter(BPF).The proposed MIM capacitor was consisted of a pair of square patches printed on each side of the dielectric substrate.It has a capacitance of 5.26 pF,which is much larger than that of the conventional interdigital capacitor.The proposed MIM capacitor was embedded into the inside space of a conventional open loop resonator(OLR)to form a slow-wave OLR.This new slow-wave OLR was used to design a miniaturized 2 nd-order slow-wave BPF.The size reduction of 40%was achieved comparing with the interdigital capacitor loaded slow-wave BPF.The frequency range in which the insertion loss in the stopband is larger than 20 dB is up to 4.46 times of passband center frequency,showing that the proposed BPF has a wide stopband.The measured results showed excellent agreement with the simulation.