一种新型小型化宽带无人机机载智能天线研究

随着无人机系统的发展,无人机无线链路需要具有智能波束跟踪能力的小型化宽带高增益定向波束实现无线连接与组网。以电抗加载理论为基础,研究一款机载电控无源阵列天线(ESPAR),为了实现宽带效果,中心部位馈电的主振子以单锥天线作为激励,以寄生单元高度、单元间间距和加载电抗参量为优化参量,经过参数扫描、筛选和优化,给出了仿真结果,并进行了样机制作,给出了测试结果,实现了机载智能天线的小型化与宽带化。     

基于抛物面反射器馈电的多波束CTS阵列天线设计

本文设计了一种工作于Ku频段的多波束连续横向枝节（CTS）阵列天线,该天线通过切换馈电端口实现多波束扫描。该天线主要由抛物面反射器波束成形网络（BFN,beamforming networks）以及CTS辐射枝节两个部分构成,结构简单,采用PCB（印刷电路板）工艺制作。其中抛物面反射器波束成形网络包括基于SIW的H面扇形馈电喇叭以及抛物面反射器平面波转换结构;辐射部分为串馈CTS天线,通过预偏20°实现H面正方向波束扫描。天线工作在12.5GHz,通过改变馈电喇叭可实现0°-60°的大扫描角度。     

基于电调超表面及柱面反射面的相控阵天线设计

提出了一种基于电调可重构超表面的低成本相控阵天线。该天线结构由天线底部的抛物线反射面馈电网络、上层的波导缝隙阵列及在波导中加载的电调超表面3部分组成,通过抛物线反射面将馈源在天线下层平板波导中产生的柱面波转换为平面波并用来激励天线上层的波导缝隙阵列。为了实现低成本的波束扫描,在每条独立的波导缝隙天线前端加载了具有360°相位调制能力的电调超表面。通过改变变容二极管上的偏置电压的大小可改变超表面的透射相位,实现连续的波束扫描能力。该天线可实现±30°的连续波束扫描,最大副瓣电平值为-13 dB,增益变化为-2 dB。该天线的低成本、高效率的波束扫描特性使其非常适合应用在一些低成本的雷达及通信系统中。     

宽角扫描的圆极化相控线阵

设计了一款宽波束的圆极化天线单元以及1×4的天线阵列，实现了一维的宽角圆极化扫描.天线单元由单层的辐射贴片和介质基片集成波导（substrate integrated waveguide，SIW）背腔构成，通过在辐射贴片上切角微扰和开U型槽实现右旋圆极化，并利用SIW背腔缝隙展宽波束.同时利用SIW背腔减小阵列单元间的互耦，实现宽角圆极化扫描.仿真与测试结果表明，天线阵列实现了扫描角为-53°~57°，3 dB波束宽度覆盖范围为-76°~79°，在主波束扫描覆盖范围内轴比（axial ratio，AR）均小于3 dB，且在扫描范围内增益变化平稳，可实现良好的宽角范围的圆极化扫描特性.     

双H形缝隙18 GHz透镜天线设计

提出了一种新型缝隙透镜天线结构。采用微带贴片加载透镜天线结构,即通过双H形槽耦合馈电实现圆极化激励,并在天线正前方加载合适介质透镜的天线结构,使天线的波束得到了适当压榨,且增益得到了提高,驻波比和轴比也均得到了改善。同时,该天线结构还具有结构紧凑、馈电简单、易于制造的优点。     

Ku频段宽带相控阵天线技术研究

阵列天线易于实现高增益、波束扫描及波束赋形等功能,成为现代无线通信、导航、雷达等信息系统收发信号的主要手段。为满足高速率、广覆盖、多功能等发展需求,现代无线信息系统要求阵列天线具有宽工作带宽、宽角波束扫描能力及平面化、低剖面等特性。为此,文中以Ku频段、低剖面、宽频带相控阵天线为研究方向,基于微带天线宽带化技术、L型探针耦合馈电技术及加载等效腔体结构,开展微带天线的宽带化和相控阵天线的宽角扫描技术研究。文中提出了一种基于L型探针耦合馈电结构的具有宽带、宽角扫描能力的8×8阵列天线。实测结果表明,在VSWR<3时,在13.0～18.0 GHz阻抗带宽内(相对带宽为32.3%),该阵列天线在E面和H面均可实现±60°的扫描覆盖范围。实测结果和仿真结果具有较好的一致性。     

Ku波段宽角扫描圆极化微带阵列天线设计

提出了一种三馈电圆极化微带天线。天线馈电网络采用一分三功分馈电,实现微带贴片天线的圆极化辐射,增加方向图的旋转对称性。用该天线作为阵列单元,采用顺序旋转布阵技术组成一个3×4阵列,有效地改善了阵列天线的增益扫描特性。研究了该阵列天线波束扫描时的辐射特性和极化特性。仿真结果表明:阵列天线在中心工作频率处能实现俯仰60°的扫描,在扫描范围内增益大于11.9 d Bi,轴比小于2 d B。     

边射波束和锥状波束可重构的微带贴片天线

本文提出了一种边射波束和锥状波束可重构的新型微带贴片天线,该天线在锥状波束模式下具有圆度较好、锥角可设计的优点。首先,在贴片的中间引入一排短路孔,当短路孔两侧的探针反相馈电时,贴片上两侧电流同向,辐射边射波束;而当两个探针同相馈电时,贴片上两侧电流反向,辐射锥状波束。接着,对短路排孔与贴片边缘之间的间距进行了优化设计,调整电流分布,从而改善锥状波束在方位面上的圆度。最后,在贴片的对角线上额外引入了四个短路孔,通过控制其位置和大小来调节固定频率下贴片的尺寸,从而设计出不同锥角的锥状波束。通过全波仿真,设计了三个边射波束和锥状波束可切换的贴片,锥状波束的锥角分别为55°、50°和45°,均具有较好的圆度。     

宽带极化与方向图可重构天线研究

随着无线通信系统的快速发展, 宽带可重构天线将在未来发挥巨大作用.文中综述了四种宽带极化与方向图可重构天线, 它们都具有提高通信系统容量, 消除极化失配, 扩大辐射范围等特点.首先介绍了一种宽带的多线极化可重构天线.此款天线基于L型探针馈电的贴片天线, 实现了0°, 45°, 90°以及—45°极化的选择, 具有宽带、低剖面、高增益的特点.其次, 同样基于L型探针馈电的贴片天线, 通过引入一个输出相位可重构的功分馈电网络, 实现了宽带的圆极化可重构天线, 其同样具有宽带、低剖面、高增益的特点.除了极化可重构天线, 文中还介绍了两款方向图可重构天线, 可分别实现线极化以及圆极化的全向锥状波束以及定向辐射波束的方向图可重构.前者是基于宽带的单极子贴片天线跟L型探针馈电的贴片天线的有机结合.后者是基于环缝隙的贴片天线配合激励端口可重构的功分馈电网络的组合.此两款天线均具有结构紧凑、宽带、增益稳定的特点.     

基于石墨烯的波束可重构太赫兹天线

设计了一种工作在太赫兹(THz)频率下的微带八木(QYU)天线.该天线由金属微带传输线、金属反射器、金属半圆形辐射贴片和三组单分子层-石墨烯-贴片导向器组成.由于石墨烯的电导率可电调谐特性,可以通过调整施加在石墨烯导向器上的偏置电压来动态调控天线的辐射方向.通过对天线的基本性能和可调特性系统地模拟和优化,数值结果表明,通过改变加在石墨烯导向器的偏压,天线的主辐射波瓣角φ(方位角)可以在30°-150°的范围内进行扫描,并且具有非常快的调制速度和非常低的回波损耗.该天线非常适合于相控阵雷达等THz波束可重构应用。     

λ/64‐spaced compact ESPAR antenna via analog RF switches for a single RF chain MIMO system

In this study, an electronically steerable parasitic array radiator (ESPAR) antenna via analog radio frequency (RF) switches for a single RF chain MIMO system is presented. The proposed antenna elements are spaced at λ/64, and the antenna size is miniaturized via a dielectric radome. The optimum reactance load value is calculated via the beamforming load search algorithm. A switch simplifies the design and implementation of the reactance loads and does not require additional complex antenna matching circuits. The measured impedance bandwidth of the proposed ESPAR antenna is 1,500 MHz (1.75 GHz–3.25 GHz). The proposed antenna exhibits a beam pattern that is reconfigurable at 2.48 GHz due to changes in the reactance value, and the measured peak antenna gain is 4.8 dBi. The reception performance is measured by using a 4  4 BPSK signal. The measured average SNR is 17 dB when using the proposed ESPAR antenna as a transmitter, and the average SNR is 16.7 dB when using a four‐conventional monopole antenna.     

Reactance domain MUSIC algorithm for electronically steerable parasitic array radiator

Conventional adaptive array antenna processing must observe signals on all of the array antenna elements. However, because the low-cost electronically steerable parasitic array radiator (ESPAR) antenna has only a single-port output, none of the signals on the antenna's parasitic elements can be observed. A direct application of most of the algorithms for the conventional adaptive array antenna is impractical. In this paper, A technique of estimation of direction-of-arrivals (DoAs) is proposed for the ESPAR antenna. This technique is based on the modified MUltiple SIgnal Classification (MUSIC) algorithm. The correlation matrix used in the MUSIC algorithm is estimated from the signal received through the single-port output of the ESPAR antenna as it switches over a set of antenna patterns. Simulation results show that DoAs can be estimated by the reactance domain MUSIC algorithm for ESPAR antennas. Furthermore, the statistical performance on estimation error variance of the reactance domain MUSIC estimator is analyzed and compared with the Crame/spl acute/r-Rao lower bound. Analytic and empirical results show that high-resolution DoAs estimation can be achieved by using the reactance domain MUSIC algorithm for ESPAR antennas.     

Blind concurrent beamformer

The electronically steerable parasitic array radiator (ESPAR) is a smart antenna based on the adjustment of reactances at parasitic elements. A new blind beamformer is presented, for use with reactance domain arrays, such as the ESPAR. Two stochastic gradient algorithms work concurrently so that two distinct cost functions are simultaneously minimised. Results show that the new blind beamformer presents a faster convergence and a lower steady-state mean squared error     

一种新型多频缝隙微带天线的设计

提出了一种新型多频缝隙微带天线,该天线的结构与一般的微带缝隙天线结构类似,通过采用电抗加载与双支节馈电,可灵活控制其多频工作特性;通过大量计算与实验,充分地研究了其输入阻抗特性、辐射与增益特性。计算与实测的数据结果表明,该天线能在2.4～2.5GHz/5.15～5.35GHz/5.725～5.825GHz频段内获得良好的输入特性和辐射特性,因而该设计方法是正确有效的。     

ESPAR array design for the UHF RFID wireless sensor communication system

In this paper, in order to improve the received signal strength (RSS) and signal quality, three arrays of electronically steerable parasitic array radiator (ESPAR) antennas are suggested for the ultra-high frequency (UHF) radio frequency identification (RFID) communication and sensing system applications. Instead of the single antenna, the array antennas have recently been widely used in many communication systems because of their peak gains, better radiation patterns, and higher radiation efficiency. Also, there are some important issues to use the antenna array like high data rates in wireless communication systems and to better understand the many targets or sensors. In this article, a wireless sensor network (WSN) is being investigated to overcome multipath fading and interference by antenna nulling technology that can be achieved through beam control ESPAR array antennas. The proposed ESPAR array antennas exhibit higher gains like 9.63, 10.2, and 12 dBi and proper radiation patterns from one array to another. Moreover, we investigate the mutual coupling effect on the performance of array antennas with different spacing (0.5λ, 0.75λ, λ) and configurations. It is found that the worst mutual coupling reduced by −28 to −34 dB for 2 × 2 array, −3 to −43 dB for 2 × 3 array, and finally −42 dB to −51 dB due to the antenna spacing from 0.5λ to λ. Thus, these suggested antennas could effectively be applied in the WSN communication systems, internet of things (IoT) networks, and massive wireless and backscatter communication systems.     

T形天线的研究

系统地研究位于山谷间T形天线的电特性.采用矩量法求解天线和地面上的静电荷分布密度及电流分布密度,进而计算了T形天线与地面之间的静电容和天线的输入电抗,数值结果与实验结果吻合良好.同时研究了引线及顶线的各项参数变化对天线的有效高度、增益、输入电抗、辐射电阻及静电容的影响.研究表明,增加引线数目、引线间距和加长顶线长度均可以增加天线系统的静电容,减小输入电抗的模值,并使天线的增益有所改善.     

Design of CPW-fed asymmetric slot UWB antenna for wireless application

A compact Ultra-WideBand(UWB) slot antenna is presented in this paper. The slot is modified rectangular in shape and asymmetrically cut in the ground plane. A hexagonal patch with two stepped CoPlanar Waveguide(CPW) feed is used to excite the slot. Wider impedance bandwidth is achieved due to the extra inductive reactance created by the asymmetric slot which neutralizes the capacitive reactance of the hexagonal patch. The measured impedance bandwidth of the proposed antenna is 11.85 GHz(2.9–14.75 GHz). The radiation patterns of the proposed antenna are obtained and found to be omni-directional in H-plane and bi-directional in E-plane.     

船载短波鞭状天线的设计

在分析电小天线理论的基础上,设计了一款适用于船载通信的短波鞭状天线。天线体高度为2 m,内径为100 mm,利用HFSS电磁仿真软件建立了仿真模型。通过电抗加载来改善天线低频段阻抗特性,并在天线馈电端进行匹配网络设计,使天线在5 MHz~15 MHz频段内阻抗平稳,有效增加了带宽;通过天线结构的改进,有效提高了天线效率,增益达到-15 dB(5 MHz~9 MHz)和-10 dB(9 MHz~15 MHz),电压驻波比小于1.8,交叉带宽大于500 KHz。并且其结构紧凑,体积小,抗风能力强,符合船载环境下天线的设计需求。     

Electrically steerable passive array radiator (ESPAR) antennas

A novel ground-plane shape to improve the horizontal gain for electrically steerable passive array radiator (ESPAR) antennas is investigated. The peak directivity of a monopole antenna with a finite ground plane, such as a circular or rectangular ground plane is at a higher angle from the horizon. Thus, the horizontal gain is lower than that of a dipole antenna. Using a circular ground plane of a half-wavelength radius with a skirt of a quarter wavelength wound around it, the angle of the peak directivity and the horizontal gain for the ground-based communication system were improved. For an ESPAR antenna - one of the monopole arrays - the horizontal gain was also improved. It was confirmed that it was possible to form the main-beam radiation and a beam in the horizontal plane, each in an arbitrary direction, by changing the control voltage to the passive element. This was shown by an experiment with an ESPAR antenna with a finite reflector, a feed element, and seven passive elements.