使用非均匀特异媒质覆层的高增益谐振腔天线

采用非均匀特异媒质覆层,设计了一种具有高增益特性的新型谐振腔天线。该谐振腔天线采用矩形微带贴片天线作为辐射单元,安装在金属谐振腔内,其谐振频率为10 GHz。为提高天线增益,将腔表面安装蚀刻在微带基板上,由周期性单元组成特异媒质覆层。迥异于常规的单元尺寸均匀一致特异媒质覆层,本文研制的非均匀特异媒质覆层包含9×9个矩形单元,单元大小渐变。仿真表明,与常规均匀特异媒质覆层相比,该新颖的非均匀特异媒质覆层相当大程度提升了天线定向辐射性能：天线增益提高1.2 dB(从20.3 dBi增加到21.5 dBi),天线的旁瓣得到了抑制,主旁瓣比下降5 dB;同时,天线谐振频率和阻抗带宽等其他性能基本保持不变。     

高增益高效率的Fabry-Perot谐振腔天线研究

提出了一种采用非均匀频率选择表面（frequency selective surface, FSS）盖板以及非均匀电磁带隙（electromagnetic band gap, EBG）结构反射地板的高增益Fabry-Perot（F-P）谐振腔天线. 基于漏波理论模型,针对大口径F-P谐振腔天线设计非均匀的FSS盖板和EBG反射地板,控制衰减常数α和相位常数β,改善了口径场上幅度相位分布的均匀性,并抑制了非谐振频率时天线辐射性能的恶化,实现高增益和高口径效率的同时,保证了天线的工作带宽. 所提出的圆形F-P谐振腔天线直径为6.6λ₀,仿真增益为24.6 dBi,口径效率达67.9%,阻抗带宽为4.1%,3 dB增益带宽为3.7%;实测增益为23.9 dBi,口径效率达56.9%. 由于对口径场均匀性的设计,该天线克服了传统F-P谐振腔天线的口径效率和增益间的相互限制.     

基于多层介质覆盖层的高增益Fabry-Perot天线设计

提出一种由不同厚度和不同面积的多层介质板叠加制作多层介质覆盖层,代替传统单层介质覆盖层,提高Fabry-Perot(F–P)谐振腔天线增益和口径效率的设计方法。以工作频点5.8 GHz的F–P谐振腔天线设计为例,采用微带贴片天线作为馈源,由多层厚度分别为1 mm,1 mm和1.5 mm,直径分别为160 mm,130 mm和120 mm,相对介电常数为16的聚四氟乙烯介质板叠加制作该天线覆盖层。天线样品的测试结果与设计仿真结果吻合良好。与传统单层介质覆盖层相比,该多层介质覆盖层将工作频率5.8 GHz处天线增益由18.2 dBi提高到19.1 dBi,相应口径效率由70.02%增加到86.14%,天线|S11|<-10 dB阻抗带宽和3 dB增益带宽略有提高,分别达到8.19%和11.90%。     

宽带介质覆层Fabry-Perot 谐振腔天线设计

结合传输线理论和史密斯圆图分析,文中提出了一种利用全介质部分反射覆层构造宽带Fabry鄄Perot 谐振腔天线的方法。所设计的覆层结构在工作频带内拥有正斜率的反射相频特性,可满足谐振腔天线的宽带谐振条件。运用该方法设计了工作于Ku 频段的宽带Fabry鄄Perot 谐振腔天线,通过仿真计算和样件加工测试验证了该方法的正确性和有效性。     

基于非均匀特异媒质的赋形天线设计

在PCB板表面蚀刻不同尺寸的微带单元结构,构建非均匀特异媒质层,并将其放置在天线辐射单元前方,利用非均匀特异媒质层对电磁波不同的反射系数,实现对天线辐射波束的赋形。设计了由不同尺寸正方形贴片组成的非均匀特异媒质层,并放置于工作频率为5.8 GHz的矩形贴片天线前方。仿真和测试表明:该非均匀特异媒质层能够在基本保持贴片天线工作频点和回波损耗曲线不变条件下,通过调整与贴片天线距离,实现辐射波束由笔形波束向宽角波束和马鞍形波束的赋形转换。为赋形天线设计提供了一种有效的新方法。     

带内低RCS的高增益宽带Fabry-Perot谐振腔天线北大核心CSCD

本文提出一种具有带内低RCS的高增益宽带Fabry-Perot(F-P)谐振腔天线。利用类球形地的开放谐振腔,在谐振基础上激发高次模谐振来扩展F-P天线的宽带。利用尺寸可灵活独立调节的多层PRS单元,针对主极化辐射对天线高次模下辐射的表面电场相位进行调整,以降低方向图旁瓣电平;针对交叉极化散射,能实现约180°的反射相差,然后通过棋盘式布阵来实现带内交叉极化的单站RCS缩减。最终,设计并仿真了整体天线,得到3dB实际增益带宽为33.66-38.69GHz(13.9%),最大增益为24dBi,在33.66-37GHz(9.4%)内的旁瓣电平低于-8dB。在33.6-39.2GHz带宽内,主极化入射时天线具有较低的单站RCS;而对于交叉极化入射,天线单站RCS相较于地板降低了8dB以上。     

单脉冲在有限域分层非均匀媒质中的传播与反射的小波分析法

本文应用小波变换求解了单脉冲在有限域分层非均匀媒质中的传播与发射，并将有限域分层均匀媒质作为它的特例，与用经典的Ｆｏｕｒｉｅｒ变换导出的结果相比较，二者完全一致，从而证明了小波变换方法的正确性，但更重要的也更有意义的是小波变换方法解决了Ｆｏｕｒｉｅｒ变换无法解决的分层非均匀媒质情形。     

一种两宽带天线共口径的设计

 给出了一种两宽带天线共用一个口径的设计.天线制作在420×200mm²的PCB板上,其中一副天线由阻抗加载的矩形及倒L形金属片构成,两者之间使用了一个低通匹配网络进行连接.此天线实现30~600MHz驻波比小于3的宽带匹配,其中86~110MHz之间为陷波设计.另外一副天线采用开式套筒结构,实现了800~1200MHz驻波比小于2.2的设计.利用天线1的低通匹配网络作为天线2的开式套筒,从而实现了共口径设计.     

一种新型基站天线的非均匀网格FDTD分析

板状振子型基站天线是一种现代移动通信中广泛使用的基站天线。为了比较准确地对其天线单元和槽形板进行建模,同时考虑到计算资源限制,该文应用一种非均匀网格FDTD方法对其辐射方向图特性进行了分析。数值结果表明该文方法处理天线辐射问题的有效性。     

非均匀阵列天线超分辨测向性能分析

目前应用较多的是均匀线阵智能天线系统,与均匀天线阵相比,非均匀线阵智能天线系统能够使能量传送得更集中,扩大系统的覆盖区域。但是利用非均匀阵进行DOA估计,也容易出现估计模糊。计算机仿真结果表明,16元非均匀阵比16元均匀阵方向图的主瓣更窄、测向分辨率和精度更高。但是非均匀阵对低信噪比比较敏感,在信噪比较低的情况下,非均匀阵在少数特殊方向上会出现估计模糊。除去特殊方向,在相同信噪比条件下非均匀阵的分辨概率更高。     

基于口面场方法的W波段高口面效率单脉冲卡塞格伦天线

本文提出来一种应用于直升机防撞雷达的高口面效率W波段单脉冲双反射面卡塞格伦天线。口面分析方法的提出解决了W波段反射面天线口面相位分布不均匀的缺陷,从而有效的提高了口面的利用效率。利用该方法,本文研究并制作了口径为135mm、焦距为40.5mm的W波段卡赛格伦天线,并且设计了由四个E面多缝隙电桥和四个四分之一波导波长延迟线级联构成的和差网络。经测试,该单脉冲天线在93GHz具有38.6dBi的和波束增益,相应的口面效率为54.7%;差波束的零深优于-22dB,副瓣电平小于-18dB。测试结果与基于口面分析方法的仿真结果吻合,从而证明了本文所研究天线可以应用于高口面效率的W波段单脉冲系统中。     

Step-horn antenna with high aperture efficiency and low cross-polarisation

A multi-step horn antenna with rectangular or circular cross-section is presented. The horn has about 90% aperture efficiency and low cross-polarisation level. The theory behind such high aperture efficiency is explained and the radiation and return loss characteristics are shown.     

A novel non-uniform spacing coherent heterodyne WDM system with high channel efficiency

A novel non-uniform spacing coherent heterodyne wavelength division multiplexing (WDM) system is proposed, analyzed and investigated in this paper. High channel efficiency is realized by reducing the average channel space to half the value of the traditional uniform spacing WDM systems. Simulation shows that the proposed scheme exhibits excellent laser line width toleration of 10 MHz and channel space deviation toleration of ± $40%. Experiment setup of 2.5 Gbit/s heterodyne WDM transmission including differential phase shift keying (DPSK) and non-return-to-zero (NRZ) channels is established to investigate the scheme.     

A novel design of circularly polarised antenna based on metamaterial

This article presents a novel design of circularly polarised microstrip antenna based on a metamaterial reflection plane and a half-wave antenna. The metamaterial is composed of two pieces of substrates coated on one side with split ring resonators. Both the experimental and simulated results show that good circularly polarised radiation performances are obtained. The 10?dB return-loss impedance bandwidth and 3?dB axial ratio bandwidth of proposed antenna are 12% and 7%, respectively, and the gain of proposed antenna compared with the half-wave antenna is improved from 6?dB to 9?dB in the design frequency range.     

A small dipole-fed resonant reflector antenna with high efficiency, low cross polarization, and low sidelobes

The computer-aided optimization of a small five-wavelength diameter reflector antenna with a center-supported dipole-disk feed is described. The primary radiation is controlled by using a patented beamforming ring to give low cross polarization and low sidelobes due to spillover. The efficiency is maximized by controlling and taking advantage of the multiple reflections between the feed and the reflector. This has inspired the name "resonant reflector antenna." The gain from the feed reflector resonances is so large that it compensates almost completely for the about 1 dB loss due to center blockage of the aperture.     

High efficiency and low sidelobe design for a large aperture offset reflector antenna

A design method giving high efficiency and low sidelobes is discussed for large aperture offset reflector antennas. A new reflector shaping technique using the subreflector and the beam waveguide reflector with the parabolic main reflector is proposed to simplify the main reflector manufacturing process. The effectiveness of the technique is confirmed by the model experiments. One problem with this reflector shaping technique is that the subreflector edge level cannot be controlled independently of the main reflector edge level. By investigating the relation between the gain reduction and the subreflector edge level, which affects the wide-angle sidelobe levels, the realizable characteristics of antennas are studied. In order to decrease the subreflector edge level without reducing the aperture efficiency, a technique using an extended reflector is also proposed. Its effectiveness is shown by theoretical and experimental investigations.     

A LLC resonant converter with dual resonant frequency for high light load efficiency

This paper presents a new approach to achieve high light-load efficiency for inductor-inductor-capacitor (LLC) resonant converters. Compared with the conventional LLC resonant converters, an additional active resonant network is employed to give the proposed converter another resonant frequency and another steady state. Thereby, the proposed converter has advantages of narrow switching frequency range and high light-load efficiency. The operation principle and the resonant network switching strategy of the proposed converter are analysed, as well as the design considerations. A 1.2-kW prototype with silicon carbide (SiC) MOSFETs is built to verify the proposed converter. The peak efficiency is tested as 94.4% at 680 kHz. Especially, the light-load efficiency is improved from 89% to 91%.     

基于高阻表面和波纹槽结构的法布里-珀罗天线研究

针对尺寸有限的法布里-珀罗(Fabry-Perot,FP)天线副瓣较大、增益带宽窄的问题,提出了一种基于高阻表面和波纹槽结构的新型FP天线模型.同时使用三维全波电磁场仿真软件CST就传统FP谐振结构、周期性以及非周期性加载高阻表面阵列和波纹槽结构对天线辐射性能的影响进行数值分析.模拟和实验测试结果表明:与传统FP谐振结构相比,加载周期结构仅能在较窄频带内提高天线增益,而加载非周期结构能使该天线增益在更宽频带内得到提高且其增益稳定性更好.