基于枝节加载型SIR的可调滤波器

Tunable filter based on stub-loaded SIR

基于枝节加载型阶梯阻抗谐振器(SIR)设计了一种加载变容二极管的微带可调带通滤波器。SIR结构利于抑制高次谐波且可实现滤波器的小型化,提出的模型通过在SIR的中心平面加载2个枝节构成多模谐振器。通过奇偶模方法分析了枝节加载型SIR的谐振特性;通过加载变容二极管实现了对滤波器奇偶模谐振频率的独立控制,利用变容二极管容值的变化实现了滤波器的中心频率可调,中心频率随变容二极管偏置电压的增加而增大。该可调滤波器实现了在0.82～1.17GHz范围内中心频率可调且插入损耗小于5 dB,回波损耗大于10 dB。

A microstrip tunable band-pass filter based on stub-loaded Stepped Impedance Resonator(SIR)is designed,which is loaded with varactors.The SIR structure facilitates the suppression of higher harmonics and enables miniaturization of the filter.The model proposed in this paper is a multimode resonator consisting of a SIR and two stubs loaded in the center plane of the SIR.First of all,the resonance characteristics of the stub-loaded SIR is analyzed in the even-odd mode analysis method.Then,the independent control of the odd mode and even mode resonant frequency of the filter is realized by loading varactors.The tunability of the center frequency can be realized by adjusting the capacitance of the varactors.The center frequency increases with the increase of the bias voltage of varactors.The tunable filter shows a center frequency tunable range from 0.82 GHz to 1.17 GHz with less than 5 dB insertion loss and more than 10 dB return loss.