基于枝节加载多模谐振器的电调微波滤波器设计

Design of Electronically Tunable Microwave Filter Based onStub Loaded Multimode Resonator

针对认知无线电技术对射频微波滤波器的新要求,提出了一种基于枝节加载多模谐振器的电调微波滤波器;该电调微波滤波器由一个枝节加载微带多模谐振器和变容二极管组成,实现了滤波器的小型化;在分析枝节加载微带多模谐振器的基础上,通过在微带谐振器两端和加载枝节上加载变容二极管的方法,设计了枝节加载的电调多模微带谐振器,并提出了复杂微带谐振器谐振特性的分析方法;采用源和负载耦合的方法在通带右边引入一传输零点;通过在源和负载端放置耦合线的方法,提高了滤波器的通带选择性;针对滤波器带外衰减小的问题,引入一种新型的频变馈电结构,改善了滤波器的带外衰减特性;通过优化仿真确定了电调滤波器的尺寸参数;仿真验证了该滤波器的特性,当变容二极管的可调范围为2~10 pf时,滤波器的频率可调范围为2.10~2.40 GHz,频率变化范围为300 MHz。

In response to the new requirements of cognitive radio technology for radio frequency microwave filters,an electronically tunable microwave filter based on the stub-loaded multimode resonator is proposed.The electronically tunable microwave filter is composed of a stub-loaded microstrip multimode resonator and varactor diode,which realizes the miniaturization of the filter.Based on the analysis of the stub-loaded microstrip resonator,a stub-loaded electronically tunable microwave multimode microstrip resonator is designed by the method of loading varactor diodes on both ends of the microstrip resonator and the loading stub-loaded,and the analysis method of resonance characteristics for the complex microstrip resonator is proposed.A transmission zero is introduced to the right of the passband by means of source and load coupling.The passband selectivity of the filter is improved by placing coupled lines at the source and load end.Aiming at the problem of small out-of-band attenuation of the filter,a new type of frequency-dependent feed structure is introduced to improve the out-of-band attenuation of the filter.The size parameters of the electronically tunable microwave filter are determined by optimization simulation.The characteristics of the filter are verified by simulation.When the adjustable range of the varactor diode is 2~10 pf,the frequency adjustable range of the filter is 2.10~2.40 GHz,and the frequency change range is 300 MHz.