【作者】 特尼格尔；

【导师】 张宁； 邱景辉；

【作者基本信息】 哈尔滨工业大学 ， 信息与通信工程， 2014， 博士

【摘要】 在科技发展的时代，通信速率、通信容量不断提高，与之对应的通信设备也在不断发展，传统的窄带天线已经不能满足现代通信的要求，取而代之的是频带更宽，体积更小的宽带天线。同时，在现代无线电监测，电磁兼容测试，广播测试中往往需要几百兆到几十吉赫兹的频率范围，对于这些工作来说，传统窄带天线不仅大大增加了设备成本，而且为了满足不同频段测试需求时，需要架设相应的天线，这也大大降低了工作效率。因此宽带天线广泛应用于上述领域。为了适应未来无线通信的发展，天线不仅要追求宽频带的特性，同时还要兼顾到小型化，极化和带内方向图稳定性以及增益稳定性等诸多问题。由于天线的性能在很大程度上是由尺寸来决定的，这是客观存在的事实，因此只要遵循客观规律，也可在天线电气性能指标与尺寸间取得折中。本文首先对能够产生超宽频带阻抗带宽的主要结构进行了理论分析与比较研究，这些结构包括半开放形式的平面渐变线结构、封闭形式的加脊波导结构以及开放形式的双锥结构。重点对这些结构产生超宽带能量传输的机理进行了分析，所得到的分析结果为后续各章的天线分析与设计提供了理论基础。其次，提出了一种剖面低、方向图带宽宽、增益高且副瓣电平较低的新型平面加载喇叭天线。仿真与实验结果表明，对传统对拓Vivaldi天线沿轴线方向进行矩形槽缝加载，能使得天线的频带下限降低9%，从原来的4.4GHz降低到4GHz，而频带上限未受影响；对矩形槽缝加载的Vivaldi对拓天线在口面上进行平面介质透镜加载，能够展宽天线的方向图带宽，这是因为加载的透镜克服了传统对拓Vivaldi天线在高频端由于口面相位误差增大，而导致的方向图分裂的问题；对矩形槽缝加载的透镜对拓Vivaldi天线在口面上进行Choke槽缝结构的加载，能降低天线辐射张角末端的横向电流对主辐射方向图的影响，进一步提高天线在高频端的辐射增益和降低副瓣电平。所提出的新型平面加载喇叭天线的测试结果为：工作频带为4-30GHz，带内增益5-8dBi，方向图的前后比高于13dB，没有分裂现象。再次，提出了一种结构尺寸小、方向图带宽宽、增益高且副瓣电平较低的新型加载双脊喇叭天线。仿真与实验结果表明，在双脊喇叭的脊上加载一对金属槽，能提高脊间端口阻抗的稳定性，有效地拓展天线的阻抗带宽，和传统双脊天线相比，天线的频带下限降低了60%，即从5GHz降低到了2GHz；在喇叭天线口面处加载根据费马原理设计的具有单双曲柱面边界的介质透镜，能改善喇叭口面的相位分布，显著拓展天线的方向图带宽，与未加载透镜的情况相比，天线的方向图带宽上限提高了82%，即从22GHz提高到了40GHz；在加脊喇叭的馈电波导内部加载楔形金属块，能够抑制高次模，保证主模传输的稳定性，显著提高天线的增益带宽，和未加载楔形金属块的情况相比，天线的增益带宽上限提高了82%，即从22GHz提高到40GHz，并首次采用模式分析的方法解释了增益带宽提高的机理。所提出的新型加载双脊喇叭天线测试结果为：工作频带为3.2-40GHz，带内增益从5dBi升至20dBi，方向图的前后比高于15dB，没有分裂现象。最后，提出了一种具有不同轴双锥结构的带有介质透镜加载的新型双锥喇叭天线。这种新型天线是在一种小型化的介质加载全向辐射双锥天线的基础上通过锥体倾斜以及切削尾部的方法实现的。仿真与实验结果表明，双锥天线具有超宽的阻抗带宽，可达20:1(1-20GHz)，而介质加载可以使全向辐射的双锥天线整体尺寸显著下降，在保证阻抗带宽不变的情况下，锥体底面直径可以从150mm降低至96.6mm，下降了35.6%，这为双锥喇叭天线的宽带和小型化提供了保证；锥体倾斜可以压缩一侧波束，提高天线的定向性；通过加载专门设计的椭圆柱面边界的介质透镜，能够进一步压缩波束，提高天线增益。最终所提出的新型双锥喇叭天线测试结果为：工作频带为2-20GHz，带内增益从3dBi单调上升至17dBi，方向图的前后比高于15dB，没有分裂现象。本文着重研究了超宽带喇叭天线特性，通过理论分析、仿真和实验的方法，重点分析了平面喇叭、加脊喇叭、双锥喇叭天线，并利用以介质加载为主的多种加载方式，改善了传统形式的上述天线在工作频带内性能指标不稳定等缺点，旨在为超宽带喇叭天线的发展寻求更深入有效的理论基础、实验论证和优化设计途径。更多还原

【Abstract】 In the era of technology advancement, with the increase of communication speed and capacity and the development of communication equipments, conventional narrowband antennas can’t meet the demand of modern communication, which are being replaced by wideband antennas with wider bandwidth and smaller dimensions. Meanwhile, referring to modern radio monitoring, EMC testing and broadcasting testing, the working frequency ranges from hundreds of megahertz to tens of gigahertz. The utilization of conventional narrowband antennas both increase equipment cost and decrease the working efficiency greatly, since antennas of different frequencies are set up to meet the corresponding measurement demands. Therefore, wideband antennas are widely used in the fields mentioned above. To accommodate the development of wireless communication in the future, wide bandwidth, miniaturization, polarization and radiation pattern stability, gain stability, etc. should all be considered. Since the characteristics of antennas are determined by dimensions to a great extent, which is an objective fact, the compromise between electric performance indexes and dimensions should be made by following objective laws.Initially, antenna structures with the potential of ultra-wideband impedance bandwidth are analyzed theoretically and compared, which include gradient structures in the semi-open planar form, ridged waveguide structures in the closed form, and bi-conical structures in the open form. The mechanization of power transmission in the ultra-wide bandwidth is focused on, providing the analytical results as the theoretical foundation of antenna analysis and design in the following chapters.Secondly, a novel planar loaded horn antenna is proposed with low profile, wide radiation pattern bandwidth, high gain and low sidelobe level. The simulation and experimental results show that the rectangular slot loaded on the conventional antipodal Vivaldi antenna along the axis direction decreases the lowest working frequency by9%, from4.4GHz to4GHz, while the high frequency end is not influenced; planar dielectric lens loaded at the aperture of the antipodal Vivaldi antenna with rectangular slot can widen the antenna’s radiation pattern bandwidth by decreasing the aperture phase error in the high frequency band which leads to serious radiation pattern distortion in conventional antipodal Vivaldi antennas; Choke slot loading is introduced at the aperture of the antipodal Vivaldi antenna with rectangular slot and lens loading to decrease the effect of the transverse current at the end of the antenna radiation flare angle on the radiation pattern to improve the radiation gain in the high frequency band and lower the sidelobe level further. The measurement of the novel planar horn antenna shows that the working frequency band is4-30GHz with gain ranging from5dBi to8dBi, the front-to-back ratio of13dB and no distortion.Thirdly, a novel miniaturized double-ridged horn antenna with wide radiation pattern bandwidth, high gain and low sidelobe level is proposed. The simulation and experimental results show that a pair of metal slots loaded on the ridges of the double-ridged horn antenna can improve the stability of the port impedance and widen the impedance bandwidth of the antenna effectively. Compared with conventional ridged antennas, the lowest working frequency is lowered by60%, from5GHz to2GHz; a dielectric lens with hyperbolic-cylindrical boundary calculated by Fermat Principle is loaded at the antenna aperture to improve the phase distribution at the aperture and widen the antenna’s radiation pattern bandwidth greatly. Compared with the antenna without lens loading, the highest working frequency is increased by82%, from22GHz to40GHz; a wedge metal block is loaded inside the feeding waveguide of the ridged horn to restrain the higher modes, maintain the stability of the dominant mode, and widen the gain bandwidth greatly. Compared with the antenna without wedge metal block loading, the highest frequency of the gain bandwidth is increased by82%, from22GHz to40GHz; modal analysis is carried out to explain the mechanism of the gain bandwidth enhancement initially. The measured results of the proposed double-ridged horn antenna show that the working frequency band is3.2-40GHz with gain ranging from5dBi to20dBi, the front-to-back ratio of higher than15dB and no distortion.Finally, a novel dielectric lens loaded bi-conical horn antenna with cones of different central axes is proposed. Based on a miniaturized dielectric loaded omni-directional bi-conical antenna, the novel antenna is realized by inclining the cones and cutting the back side of the cones. The simulation and experimental results show that the bi-conical antenna can realize ultra-wideband impedance bandwidth with fractional bandwidth of20:1(1-20GHz). The dimension of the omni-directional bi-conical antenna can be decreased greatly by dielectric loading. Maintaining the impedance bandwidth unchanged, the diameter of the cone underside can drop from150mm to96.6mm, by35.6%, which guarantees the bandwidth and miniaturization of the bi-conical horn antenna; the directivity of the antenna can be increased by inclining the cones and focusing the beam; the antenna gain can be enhanced further by loading a specially-designed dielectric lens with elliptic-cylindrical boundary. The measurement of the novel bi-conical horn antenna shows that the working frequency band is2-20GHz with gain ranging from3dBi to17dBi, front-to-back ratio of higher than15dB and no distortion. The dissertation mainly focuses on the characteristics of ultra-wideband horn antennas. Planar horns, ridged horns and bi-conical horns are analyzed intensively by theoretical analysis, simulation and experiments. The instability of the above-mentioned antennas’ parameters in the working frequency band is improved by kinds of loading methods such as dielectric loading, to provide more thorough and effective theoretical foundation, experimental demonstration and optimization design methods for ultra-wideband horn antennas.更多还原