CRLH结构微带天线的小型化设计研究

运用分层媒质格林函数结合矩量法对复合左右手（Composite Right/left-handed CRLH）结构微带天线进行了准确的数值计算,由于CRLH结构在匹配性能上的不足,该结构天线在S参数性能上很难达到要求。该文提出利用量子遗传算法对CRLH结构微带天线的虚地结构进行了编程优化,大大改善了CRLH结构微带天线的S参数,对优化获得的小型微带天线进行加工制作,测试结果较为理想,并得出：改变虚地的形状、大小不仅可以优化天线的S参数,而且可以改变天线的第一谐振频率。从而为实现CRLH结构微带天线的宽频化、多频化提供了一定的理论支持。     

含有负参数媒质双层基底的宽带微带天线设计

将谐振腔引入微带结构,分析和设计了含有负参数媒质双层基底的微带天线.利用腔体内各本征模式频率参量的消除,此新型微带天线突破了传统的窄带局限.对于负参数媒质固有损耗所带来的天线性能的改变也进行了考虑.最后,将此设计应用于单负参数媒质双层基底微带天线中,同样获得了大幅度提高的带宽特性.     

一种双频双圆极化微带天线的设计

提出了一种仅利用单端口馈电的共口径双频双圆极化微带天线。天线通过在对应高端谐振频率的圆形贴片外层附加对应低端谐振频率的圆环形贴片,并采用四个窄带条连接两贴片,从而实现双频工作;通过在圆形和圆环形贴片外侧开缺口的方式实现了圆极化波辐射,并通过在两贴片上开置的缺口相正交,从而形成了低端右旋圆极化（RHCP）、高端左旋圆极化（LHCP）的特性。对提出的天线进行了仿真并优化设计,给出了该天线在两个谐振频段上具有较好的阻抗匹配和双圆极化性能。     

左手媒质基片微带天线的特性研究

将离散复镜像方法推广到左手媒质基片的格林函数计算中,并应用矩量法对左手媒质基片微带天线的辐射特性进行了研究.这种新型天线在左手媒质基片负介电常数的绝对值小于或等于负磁导率绝对值时,可以得到与传统微带天线相类似的方向图;而在负介电常数的绝对值远大于负磁导率的绝对值时,所得到的方向图具有主瓣宽度窄,仰角低的特点.针对这一全新的辐射特性,提出了左手媒质基片微带天线作为高指向性天线的应用.     

基于FSS 的双频高增益微带天线

设计并制作了一种基于双屏FSS(Frequency Selective Surface)部分反射表面的双频高增益微带天线。该FSS 结构是在介质板上下表面分别刻蚀两条方环形金属带,通过调节金属带的宽度,实现频比(Frequency Ratio,FR)达到2 的双频谐振,且在5. 12 ~5. 31GHz 和10. 08 ~10.84GHz 频带内反射相位曲线斜率为正(一般的为负),反射系数模值都在0. 86 和0. 82 以上。将FSS 以覆层的形式放置于双频微带天线上方,相当于增加了双频天线的辐射口径面积,有效改善天线的辐射性能。仿真和实测结果表明:与原始双频微带天线相比,加载双频FSS 覆层后,新天线的增益得到了提高,在5.22GHz 和10. 43GHz 处,天线鼻锥方向增益分别提高了4. 8dB 和5. 1dB。     

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。     

复镜像法分析探地雷达天线阻抗特性

为保证探地雷达天线与发射系统的良好匹配，文中采用复镜像法分析了贴地偶极天线阻抗在加载和未加载的情况下，天线阻抗随频率和地下媒质参数的变化特性。发现在300MHz到600MHz的高频情况下，天线的输入阻抗随着地下媒质的介电常数(εr=2～10)的变化较大，随媒质电导率(σ=0．0001～0．05S／m)的变化较小；在采用分布加载之后，天线的输入阻抗随着地下媒质介电常数的变化量与未加载时基本相同，但天线的频带却得到较大地加宽。     

缝隙加载H形双频天线

为了适应现代双频通信系统的要求,双频天线必须具有小尺寸和频率易调节的特点.通过在H形微带天线的辐射边附近采用U形缝隙加载,在单层微带天线上实现了双频效果.和常规的双频微带贴片天线相比,该天线的尺寸可以大大减小.通过改变天线的尺寸参数,高频段和低频段可以很容易地调节,本设计中得到频率比范围是1.716～2.363.该天线在两个频段有相同的极化平面和较宽的辐射波束.     

小型化双频带蝶形微带天线设计

提出一种同时面向全球定位系统(GPS)和无线局域网(WLAN)应用的双频带蝶形微带天线。该天线由两对尺寸不同的蝶形贴片构成,两对贴片谐振在不同的频率,从而形成相互独立的双频特性。通过商业仿真软件HFSS13.0对该双频蝶形微带天线进行仿真优化分析,结果表明,文章设计的双频带蝶形天线拥有良好的10 dB阻抗匹配带宽(第一通带为670 MHz;第二通带为1 130 MHz),可以有效覆盖GPS和WLAN的频带应用。     

一种应用于5G的双频微带天线设计

提出了一种可应用于5G无线通信的小型化双频微带天线,该天线采用偏心侧馈和贴片开槽的方式使其具有双频工作特性。首先研究了微带贴片尺寸和贴片上倒L型开槽对天线谐振频率的影响;其次通过在微带贴片的馈点旁增加矩形细缝来调节天线的阻抗匹配特性;最后,利用电磁仿真软件HFSS对所提出的天线的性能进行了仿真与优化,结果表明其两个工作频段可覆盖3.5~3.6GHz和4.8~5.0GHz的5G频段,两个工作频段内的回波损耗最大为23dB,辐射增益分别为2.83dB和4.35dB。     

Dual-frequency circularly polarised annular-ring microstrip antenna

The design of the circular polarisation (CP) for an annular-ring antenna operated at its TM/sub 11/ and TM/sub 12/ modes is presented. The CP radiations of the proposed design are achieved by placing an L-shaped strip connected to two orthogonal sides of the inner boundary of the annular patch. The dual-frequency CP operations are excited by a single probe-feed, and no additional 90/spl deg/ phase shifter and impedance-transformer circuit are required. A prototype of the proposed design was implemented and measured. Measured results show that broadside radiation patterns with good CP characteristics are obtained at the two operating resonant modes. Agreement between measured and numerical results is satisfactory.     

Microstrip Sierpinski fractal carpet for slot antenna with metamaterial loads for dual-band wireless application

The compact microstrip antennas with the dual-band characteristic and reconfigurable qualification have been noticed and investigated in this paper. We have developed the slot microstrip antenna with Sierpinski carpet and Minkowski formations and then the metamaterial loads are placed on this antenna in the slot area. The reflection/transmission method has considered to obtain the permittivity and permeability of the split ring resonator (SRR) as a metamaterial. Finally, we show that by using some junction in the metamaterial layer, we can obtain reconfigurable characteristic. Both antennas have dual-band characteristic where the first antenna has two resonances at 3.2 and 4.5 GHz and in the second antenna by altering the metamaterial layer both resonances are occurring at 3.5 and 5.8 GHz. We show that the antenna has two resonance frequencies that matched with the metamaterial Double Negative (DNG) characteristic. Both antennas are printed on FR-4 also we compared measurement and simulation results together. Aforementioned antennas cover the main wireless, WiMAX and LTE bands with sufficient gain and high efficiency (more than 80% typically) with a bi-directional radiation pattern for the indoor application. Here, the metamaterial is used for controlling the resonances and Sierpinski carpet is developed for matching.     

Low-profile dual-frequency circular microstrip antenna for dual ISMbands

A novel dual-frequency design of a singIe-layer, single-feed circular microstrip antenna for dual ISM bands is demonstrated. Due to the embedding of an offset open-ring slot in a circular patch, a novel dual-frequency operation with its two operating modes centred at about frequencies 2.4 and 5.2 GHz has been obtained. The two operating frequencies have similar broadside radiation patterns and same polarisation planes, and small antenna-gain variation. Details of the antenna design and experimental results for the proposed antenna are presented     

基于分形的特异媒质层设计及应用于提高天线增益

根据分形原理,设计了一种新颖的分形图案。通过在印刷板(PCB)上周期性地蚀刻该分形图案制作了一种微带结构的特异媒质层。仿真计算表明,随着一些分形结构参数变化,该特异媒质层对电磁波具有连续变化的反射系数幅度和相位。依据部分反射层理论,将该特异媒质层加载在矩形贴片天线前方,在天线的工作频点、带宽和定向辐射特性基本保持不变条件下,矩形贴片增益得到不同程度提高。加工制作了特异媒质层和矩形贴片天线,测试结果验证了设计和仿真计算的正确性。     

Bandwidth enhancement for dual-frequency microstrip antenna with conical radiation

A design for dual-frequency microstrip antennas with conical radiation patterns is studied. The dual-frequency operation is achieved by exciting two different resonant modes of the square microstrip patch antenna with four symmetrical shorting walls. Then, a method to enhance the impedance bandwidths of the dual-frequency antenna is proposed, and the experimental results show bandwidths are increased by 19 and 31% at the lower and higher operating frequencies, respectively. Simulation analyses are also performed to support the measured results.     

Bandwidth-enhancing ultralow-profile compact patch antenna

A novel method to extend the operation bandwidth and reduce the size of the ultralow-profile patch antenna is presented in this paper. The designed results indicate that two orthogonal modes of TM/sub 10/ and TM/sub 01/ can be excited simultaneously in the antenna, resonate at two close frequencies, and also are matched well. Thus, a bandwidth-enhancing characteristic is achieved. The size reduction is obtained due to utilizing the slot-loading technique. Because most patch currents of the two modes flow in the same direction, the similar radiation characteristics is observed at two resonance frequencies. The significantly high cross polarization makes the proposed antenna applicable for the wireless communication in multipath environment.     

Dual-frequency folded dipole antenna with PBG structure

For wideband RFID systems, a dual-frequency printed folded dipole antenna is designed with a photonic bandgap (PBG) structure carved in the antenna's arms. Simulated results show that this antenna has good return loss characteristic and hemisphere direction radiation characteristic, at two working centre frequencies of 0.90 and 2.24'GHz. Compared to other improved structures, the new PBG structure has special advantages in simplifying the antenna structure. Considering engineering processes, the influences of antenna arm width, dielectric loss, the PBG structure bore size and substrate on the performance of an antenna are particularly studied.     

A CPW-fed dual-frequency monopole antenna

A new dual-frequency design of coplanar waveguide (CPW)-fed monopole antenna is proposed and experimentally studied. The proposed antenna utilizes the advantages of the CPW line to simplify the structure of the antenna into a single metallic level, thereby making easier the integration with the microwave integrated circuits. The two operating modes of the proposed antenna are associated with various lengths of two monopoles, in which the longer monopole works for the first resonant mode and the shorter monopole works for the second mode. Moreover, by increasing the width of the longer monopole, a broadband dual-frequency operation is demonstrated. Experimental results show that the impedance bandwidth, determined from 10-dB return loss, of the two operating frequencies can both be greater than 14%. Details of the experimental results are presented and discussed.     

Miniaturization of microstrip loop antenna for wireless applications based on metamaterial metasurface

The metamaterial and fractal techniques are two main methods for antenna miniaturization and in this paper, we have modeled an especial shape of the antenna based on loop formation with metamaterial load for this aim. The metamaterial layer is made by multi parallel rings and the result shows that the final antenna size reduced drastically while the frequency shifts from 7 to 4 GHz. The antenna has Omni-directional pattern with the gain of 3.5 dBi, so the size is reduced around 40%for 4.5 GHz and another resonance is made at 2.5 GHz with a return lossless than −6 dB with more than 60% frequency shift. The reflection and transmission have been utilized for showing the left hand characteristic based on two port periodic simulations in HFSS full wave software. We show that how the metamaterial load can provide the circular polarization (CP) by controlling the current distribution. We also presented that by making slots we obtained the better Axial Ratio (AR) and miniaturized the antenna with reconfigurable qualification. As a result of fact, we show that by using metasurface we able to miniaturized the antenna and simultaneously achieved the circular polarization.     

应用于WLAN的宽频带天线设计

为了设计出可以覆盖无线局域网WLAN的2.4GHz,5.2GHz,5.8GHz三个频带的天线,采用一种结构简单的宽带双频共面波导馈电的单极子天线。该天线由一个平面倒L形和一个倒U形贴片连接构成,实际加工制作了一个天线并且实测了S11参数,结果表明该天线具有两个独立的谐振模式,并且在应用范围内具有良好的阻抗匹配特性。