【作者】 朱晓明；

【导师】 杨晓冬；

【作者基本信息】 哈尔滨工程大学 ， 通信与信息系统， 2017， 博士

【摘要】 超宽带是具有极宽频谱资源的无线电技术,主要用于短距离高速率通信、图像传输、无线传感器网络等应用领域,而天线作为无线系统的能量转换装置,其尺寸的大小和性能的优劣对整个系统起着重要的影响作用。当超宽带技术应用于便携移动系统的终端时,则要求天线具有低剖面、小尺寸、易于与其他电路集成等特点,因此研究小型化和集成化的超宽带天线具有重要意义。为了获得好的辐射性能,通常超宽带天线以低介电常数材料作为介质基片,可天线的平面尺寸却与介电常数成反比关系,所以天线小型化一直是设计过程中的瓶颈难题。本论文研究了基于高介电常数硅材料设计小型化超宽带天线的方法,所提出的硅基天线具有非常紧凑的平面尺寸,同时硅片也是射频集成电路常用的基底,可将硅基天线与系统功能电路集成为一体,减少分离元件间的功率损耗,提高天线集成度。为了改善高介电常数硅基天线的辐射性能,本文将光子晶体结构用于天线设计中。由于光子晶体是一种介电常数周期分布的人工电磁材料,具有独特的频率带隙特性,能有效抑制硅基天线的表面波损耗。MEMS技术属于三维的微机电系统制造技术,具有微型化、集成化和批量生产等主要特点,本文将MEMS技术作为硅基天线的加工方法,保证了空腔、通孔等精细复杂微结构制作的精确性和可靠性。本论文主要研究用于小体积无线装置中的超宽带天线,利用天线技术、人工电磁材料技术和MEMS技术的多学科交叉融合,研究了新类型天线的设计和实现方法,具体的研究内容为以下几个方面:首先,基于传输线模型理论研究了平面单极子超宽带天线的设计方法,通过对矩形辐射贴片和共面波导馈电结构的改变,使天线具有了宽阻抗匹配特性。为了避免现存的一些窄带系统对天线的干扰,提出了具有双陷波特性的超宽带天线设计方法。利用天线背面附加两个偏T形寄生单元和在辐射贴片上开窗的联合方法,使陷波单元在相应频段内分别发生谐振现象,结果表明提出天线对WLAN和WiMAX频段的窄带信号起到了有效的抑制作用。其次,为了提高超宽带天线的小型化程度,采用高介电常数的硅材料作为基底,提出了硅基背腔式超宽带天线的设计方法。在天线辐射贴片的正下方刻蚀矩形腔体,形成硅和空气的混合结构,以此降低等效介电常数,减小硅基底的表面波损耗。通过MEMS工艺步骤的具体设计,主要利用光刻、蒸镀、ICP腔体刻蚀等工艺实现了硅基MEMS天线的制作,频域和时域结果表明小型化的硅基MEMS天线在超宽带频段内具有良好的全向辐射特性,并且经由天线辐射的响应信号与输入信号之间具有较高的相关性。再次,为了提高超宽带系统的传输速率和通信可靠性,以硅基背腔式天线作为MIMO天线单元,提出了二单元和四单元MIMO超宽带天线的设计方法。在小尺寸天线面积的约束下,为了减小单元天线间的互耦影响,设计了一个具有单负超材料特性的MEFSS单元结构,在整个超宽带频段内具有带阻滤波的作用。将此MEFSS单元纵向排列组成一维光子晶体结构,并放置于二单元和四单元MIMO天线中,由于天线工作频段与MEFSS单元的频率带隙范围相同,因此有效的降低了相邻和相对天线间的耦合系数,提高了MIMO超宽带天线的隔离度。再次,为了提高硅基天线的辐射效率,将以正方晶格和三角晶格周期排列的光子晶体结构用于硅基天线中,提出了光子晶体超宽带天线的设计方法。因为光子晶体能带结构中的带隙特性可以减少硅基底对电磁波的吸收,有效抑制天线表面波损耗,从而增加电磁波向外部空间辐射的能量。利用MEMS技术的光刻、蒸镀、ICP通孔刻蚀和键合等主要工艺,制作实现了具有众多微小通孔结构的光子晶体天线,结果表明基于二维光子晶体结构的天线设计方法能显著扩展天线的工作带宽。最后,为了抑制不相干信号对光子晶体天线的干扰,基于光子晶体缺陷波导的缺陷带特性,提出了光子晶体陷波天线的设计方法。当光子晶体的晶格周期被破坏而成为光子晶体波导后,电磁波会沿着缺陷方向传播,因此天线结构中的缺陷波导会改变硅基底的表面场分布,并使能量集中于缺陷位置处,而表现出谐振单元的陷波功能。通过对正方晶格和三角晶格缺陷波导的合理设计,使光子晶体天线分别实现了对X波段和Ku波段信号的陷波抑制作用。更多还原

【Abstract】 UWB is a radio engineering technology with ultra wide spectrum resource,which is mainly applied in the short-range high speed communication,image transmission,wireless sensor network and so on.The antenna is the energy conversion device of wireless systems,which size and performance have the significant influences on the whole system.When UWB technology is used for terminals of portable mobile systems,antennas should have the advantages including low profile,small size,easy to integration with other circuits and so on.It is great significant that research on UWB antenna with miniaturization and integration.To gain better radiation performance,low dielectric constant materials are generally used for designing UWB antenna.Because of the inverse relation between planar size and dielectric constant,antenna miniaturization is the choke point in design process.This paper utilizes high dielectric constant silicon material as substrates to design miniaturized UWB antennas.The proposed silicon antennas have very compact planar size.The silicon substrate is also used for RF integrated circuits,so silicon antenna and functional circuit can be fabricated together to reduce power loss of isolate elements and improve antenna integration level.Photonic crystal structure is applied in UWB antenna design processes to improve radiation performance of silicon antenna in this paper.Photonic crystal is an artifical electromagnetic material with permittivity periodic distribution,which unique frequency band gap characteristic can restrain surface wave loss of silicon substrate effectively.MEMS is the three dimensional manufacturing technology of micro electromechanical systems with characteristics of micromation,integration and quantity production.In this paper,MEMS technology is used to fabricate silicon antennas,which can realize cavity,through-hole and other subtle and complicated structures accurately.This paper researches on UWB antennas for small volume wireless equipments.The design and implementation methods of new style antennas are studied based on multi-disciplinary analysis,which includes antenna technology,artificial electromagnetic material technology and MEMS technology.The main achievements include these contents.Firstly,the design method of planar monopole UWB antenna is studied based on transmission line modal theory.The wide impedance matching characteristic of antenna isobtained by modifying rectangular radiation patch and CPW feeder.To avoid interference from existing narrowband systems,the UWB antenna with dual band-notched function is proposed.The notched elements,that are two biased T-shaped parasitic elements in the rear side and a window aperture on the radiation patch,are combined to generate resonance phenomena at corresponding frequency bands respectively.The results demonstrate that the proposed antenna prevents narrow band signal interferences from WLAN and WiMAX effectively.Secondly,high dielectric constant silicon is used as substrate to improve miniaturization of UWB antenna.The design method of silicon UWB antenna with back cavity is proposed.The back rectangular cavity is etched to form hybrid structure of silicon and air,which can lower effective dielectric constant and reduce surface wave loss of silicon substrate.The detailed MEMS processing steps are designed to fabricate silicon UWB antenna with photoetching,coating and ICP cavity etching process.The frequency domain and time domain results show the miniaturized MEMS antenna has good omni-direction radiation performance in the UWB frequency band,and high correlation property exists between input signal and response signal via antenna radiation.Then,in order to improve transmission rate and communication reliability of UWB systems,the design methods of UWB-MIMO antennas with two and four elements are proposed based on silicon antenna with back cavity.Limit to small antenna area,the metamaterial MEFSS unit with single negative electromagnetic property is designed to reduce mutual coupling between antennas,which has band-stop filtering function in the entire UWB band.The MEFSS units are arranged longitudinally to compose one-dimensional photonic crystal structure,then placed in UWB-MIMO antennas with two and four elements.Because the working frequency band of MIMO antennas is the same as band gap range of MEFSS unit,coupling coefficients of adjacent antennas and opposite antennas are decreased to improve isolation of UWB-MIMO antennas.Additionally,in order to enhance radiation efficiency of silicon antenna,the design method of photonic crystal UWB antenna is proposed by applying periodical square lattice or triangular lattice.Photonic crystal band gap of energy band structure can decrease electromagnetic wave absorption of silicon substrate,restrain surface wave loss of antenna,and increase electromagnetic wave space radiation.MEMS processes are used to fabricatephotonic crystal antenna with plenty tiny through-holes,which include photoetching,coating,ICP through-hole etching and bonding processes.The results demonstrate the antenna design method can obviously extend antenna working bandwidth based on two dimensional photonic crystal construction.Eventually,in order to restrain interference from irrelevant signals to photonic crystal antenna,the design method of notched UWB antennas with photonic crystal is proposed based on defect band characteristic of photonic crystal defect waveguides.When the periodicity of photonic crystal is broken,the electromagnetic waves propagate along defect direction.In antenna structure,defect waveguide can change surface electromagnetic distribution of substrate,concentrate energy on defect position,and present band notched function of resonance unit.After correct designing of photonic crystal defect waveguides with square lattice and triangular lattice,photonic crystal UWB antennas can respectively restrain signals from X band and Ku band.更多还原