【作者】 向乾尹；

【导师】 冯全源；

【作者基本信息】 西南交通大学 ， 通信与信息系统， 2013， 博士

【摘要】 随着现代无线通信的不断发展,在不同频段存在着大量无线通信业务,尤其是随着软件无线电技术的发展,迫切需要发展具有多频段覆盖能力且功能特性可重构的射频前端。射频滤波器是无线通信射频前端的重要组成部分,被广泛用于对频带以外射频信号的抑制,达到频带选择、抑制镜像干扰、降低接收机交调失真等目的。具有频率响应可重构特性的可调射频滤波器将是未来无线通信系统的重要支撑。本文首先回顾了近年来可调射频滤波器的发展。当前可调射频滤波器无源结构的构建主要依赖于分布式参数谐振器。面对电子器件朝向高性能、小型化发展的需求,本文基于亚波长谐振器开口谐振环SRR (Split ring resonator)与互补开口谐振环CSRR (Complementary split ring resonator),以及微带LC谐振器等平面小型化谐振结构,构建新型小型化射频带阻及带通滤波器,并研究其频率响应调控方法。在带阻滤波器方面,本文基于开口谐振环SRR及互补开口谐振环CSRR,研究新型带阻滤波器及其阻带调控方法,利用加载变容二极管的开口谐振环VLSRR(Varactor loaded split ring resonator)与共面波导耦合,成功设计出连续可调带阻滤波器；构建了加载CSRR的微带表面缺陷结构DMS (Defected microstrip structure),提出其半边电路结构,有效的降低其尺寸并提升了其通带特性,并基于此结构成功设计出1bit可调带阻滤波器。主要研究内容如下：(1)基于开口谐振环SRR,构建了一种共面波导加载SRR的带阻滤波器谐振结构。通过对其阻带调控机制的研究,利用变容二极管加载开口谐振环VLSRR,成功设计了2.19GHz～2.32GHz可调带阻滤波器。此结构中SRR采用磁耦合加载,具有良好的通频带宽和应用前景。(2)采用互补开口谐振环CSRR,构建了一种加载CSRR的微带表面缺陷结构,分析、优化了该结构带阻频率响应特性,建立了其等效电路分析模型,并提出了该微带表面缺陷结构的半边电路形式。相比原始结构该半边电路占用面积减半,且具有更小的到地电容,使得其通带性能得到提升并进一步降低了器件的尺寸。采用等效电路建模研究了该结构的阻带调控机理,提出了基于射频开关的阻带1bit可调机制,通过浮地电容与射频开关的引入,成功设计了一种具有宽带谐波抑制能力的小型化1bit2.5GHz-3GHz可调带阻滤波器。在带通滤波器方面,本文构建出基片集成波导SIW (Substrate integrated waveguide)表面加载CSRR的带通滤波器结构以及其半模基片集成波导HMSIW (Half-modesubstrate integrated waveguide)形式,提出了其通带调控方法,成功实现了具有可调通带特性的基片集成波导带通滤波器；构建了基于混合耦合的微带LC滤波器结构,研究了其通带调控方法,通过电耦合补偿带宽的方法,成功实现了恒定绝对带宽及恒定相对带宽可调带通滤波器。具体研究内容包括：(1)采用基片集成波导表面加载CSRR,在基片集成波导截止频率以下成功实现了通带,并进一步提出了其半模基片集成波导结构。通过等效电路建模研究了其频率响应的调控机制,提出了其通带调控方法,并通过机械开关、PIN二极管、变容二极管的引入,分别设计实现了lbit机械可调带通滤波器、1bit电可调带通滤波器、以及连续可调带通滤波器。此类滤波器具有较好的带内、带外特性以及较小的尺寸。(2)通过微带LC谐振器间的混合耦合,首先构建了一种二阶带通滤波器结构,研究了其频率调控机制,成功设计了基于混合耦合的电可调微带LC带通滤波器；并进一步构建了具有独立电耦合调控特性的混合耦合微带LC滤波器结构,研究了其带宽及通带的调控机制,通过电耦合补偿带宽的方法,提出了恒定绝对带宽和恒定相对带宽可调方案,基于变容二极管成功研制出微带LC形式恒定绝对带宽、恒定相对带宽可调带通滤波器；利用三阶微带LC滤波器结构,在其带外引入三个传输零点,改善了带外特性,并研究了其通带调控机制,利用变容二极管成功研制出具有宽带谐波抑制能力、良好频率选择性的三阶微带LC可调带通滤波器。本论文提出的各种新型滤波器结构及其设计方法在高性能、小型化可调滤波器设计上具有一定指导作用,同时本论文设计的各类滤波器还具有易于加工、成本低廉的特点,具有很强的实际应用前景。更多还原

【Abstract】 With the development of modern wireless communication, various wireless communication services are available in different bands. Future multi-band/software defined radio systems require building multi-band and reconfigurable radio frequency (RF) front end. RF filters are the key to constitute the channel and reduce the interferences of radio systems. Tunable RF filters with reconfigurable frequency responses will be the essential components for future wireless communication systems.In chapter Ⅰ, recent developments on tunable filters are reviewed. At present, many tunable filters based on distributed resonators are researched. With the development of modern wireless communication systems, compact and integrated devices are required. In this dissertation, novel bandstop and bandpass filters based on sub-wavelength resonators, i.e. SRR (Split ring resonator), CSRR (Complementary split ring resonator) and microstrip LC resonators are presented, and the tunable mechanics are studied.Based on SRR and CSRR the bandstop filters are proposed, and the stopband tunable mechanics of the filters are studied. VLSRR (Varactor loaded split ring resonator) loaded CPW (Coplanar Waveguide) tunable bandstop filter is designed. DMS (Defected microstrip structure) with CSRR etched on the microstrip surface is studied, and the half circuit of the structure is proposed to build a more compact bandstop filter and a1-bit reconfigurable bandstop filter. The main contributions of the work on bandstop filters are listed as follows:(1) A novel tunable bandstop filter based on CPW loaded with SRR is presented. The unit cell of the bandstop filter is formed by etching single SRR on the CPW back substrate side, and the SRR can be excited by the CPW slot’s magnetic field. Lumped equivalent circuit models are developed to analyze the frequency responses, and it shows that by loading the common cathode varactor diodes at the split region of the SRR outer ring, the resonant frequency of the bandstop filter can be electronically adjusted by tuning the reverse voltage of the varactor diodes.(2) Novel bandstop filters based on the defected microstrip structure with CSRR/half-CSRR etched on the microstrip surface are presented. By changing the configurations of the CSRR, varied stop-band and pass-band characteristics are observed, and half-CSRR is proposed to build a novel bandstop filter. A detailed explanation for the generation and variations of the stop-band and pass-band has been given. Lumped equivalent circuit analysis model is developed as well, and the frequency tuning capability of the bandstop filter is studied. It shows that the filter stopband can be reconfigured by the loading capacitance. A1-bit2.5GHz-3GHz reconfigurable bandstop filter with wide band harmonic suppression ability is designed based on the proposed novel bandstop filter loaded with floating capacitors.Novel bandpass filter is designed based on SIW embedded with CSRR, and the HMSIW (Half-mode substrate integrated waveguide) structure of the filter is proposed. The passband tunable mechanics of the HMSIW filter is studied, and tunable HMSIW filters are designed. Novel mixed coupled microstrip LC bandpass filters are presented, and the tunable mechanics of the structures are studied. Based on electric coupling coefficient compensation, a modified tunable circuit model with constant fractional/absolute bandwidth is presented. The main contributions of the work on bandpass filters are listed as follows:(1) CSRR loaded substrate integrated waveguide (SIW) and half mode substrate integrated waveguide (HMSIW) filters are proposed and their applications to mechanical and electrical tunable/switchable bandpass filters (BPF) are studied. Novel SIW and HMSIW loaded with coupled CSRR achieve forward electromagnetic wave transmission below the waveguide cutoff frequency. The half mode configuration of the proposed SIW bandpass filter is an opening structure, and the proposed HMSIW BPF is suitable to load with the control elements. The electric/magnetic coupling effects and frequency responses reconfigurable mechanics of the proposed HMSIW structure were studied based on lumped equivalent circuit model. By using floating capacitors with mechanical switches, PIN diodes and semiconductor varactor diodes loaded on the HMSIW resonators, a1-bit HMSIW mechanical tunable BPF,1-bit electrical tunable BPF, and an electrical continuous tunable BPF are demonstrated with good spurious suppression characteristics and excellent out of band rejection.(2) We propose and develop novel tunable BPF based on mixed coupled microstrip LC resonators. The equivalent circuit model of the proposed filter is presented. The filter can be reconfigured by tuning the capacitance of the LC resonators. A tunable BPF based on semiconductor varactor diode loaded microstrip LC resonators is demonstrated. Secondly, we propose and develop a novel microstrip LC filter and tunable BPFs with constant fractional/absolute bandwidth. The equivalent circuit model of the proposed microstrip LC filter is presented, and the tunable transmission coefficient of the microstrip LC filter is analyzed. It shows that the filter can be reconfigured by changing the capacitance of the LC resonators. Based on electric coupling coefficient compensation, a modified tunable circuit model with constant fractional/absolute bandwidth is presented. Finally, we propose and develop a novel3rd-order microstirp LC BPF, and three transmission zeros are obtained. The equivalent circuit model of the proposed filter is developed to study the filter’s structure. It shows that the filters can be reconfigured by changing the capacitance of the microstrip LC resonators. For demonstration, semiconductor varactor diode loaded microstrip LC resonator has been adopted in our work to design the tunable filter.更多还原