基于卦型基元的高增益超材料微带天线拓扑优化

针对超材料微带天线在拓扑优化中存在基元结构复杂导致加工高精度要求等问题,本文提出了一种极简设计理念——卦型基元;并基于卦型基元完成了超材料微带天线的拓扑优化设计,在保证天线高增益性能的同时,超材料结构构型简洁从而具有良好的可制备性。超材料结构由固定的圆弧基元和变化的卦型基元组成,其中卦型基元中每条卦线对应一个设计变量,每个设计变量的取值规则为1 对应连续卦线、0 对应断口卦线。继而以天线增益最大化为目标函数、工作频率24 GHz 为约束建立超材料微带天线设计的拓扑优化模型;并基于遗传算法的求解策略分别研究了对称型和非对称型超材料微带天线算例。分析结果表明基于卦型基元的超材料微带天线增益均得以显著提高,且四重卦线基元结构具有更大的增益;超材料结构的对称性可以保证辐射方向为Z 轴主方向;样品制备效果验证了卦型基元超材料微带天线的良好制备性;对拓扑优化设计的深入分析发现,相比方格子基元,卦型基元设计更具有高效性。最后从天线的表面波角度阐释了其高增益性能的机理。     

基于随机点阵提升天线增益的研究

增益是天线研究的重要指标,通过许多不同的方法来提高天线增益,提出了一种全新技术来提升天线增益。以矩形贴片天线为例,在矩形贴片四周排布由若干金属或空气介质小矩形块构成二维随机点阵列结构,通过遗传算法优化点阵结构,从而提高矩形贴片天线增益。设计了一款工作频点为5.8 GHz的矩形贴片天线,增加随机点阵结构后,该天线增益由7.76 d Bi提高到10.32 d Bi,口径效率由51.30%提高到91.71%,|S_(11)|<-10 d B相对阻抗带宽提高了1.59%。随机点阵结构的提出为提升天线增益提供了一种新思路。     

单馈点宽带圆极化微带天线设计

设计了一种单点馈电的宽带圆极化微带天线。针对微带天线带宽窄的问题,采用双层矩形贴片的层叠结构,通过辐射贴片之间的谐振耦合使天线的频带展宽,得到了良好的效果。在保证天线增益性能的基础上,增加了天线圆极化带宽。采用商用仿真软件HFSS对天线结构尺寸进行了优化设计,仿真结果显示,该天线工作于L波段时,VSWR<2的阻抗带宽达到10%,轴比特性良好,且在整个带宽范围内,天线增益和辐射方向图保持良好的一致性。     

基于超材料的高增益高方向性天线

分别将创新设计的两层"格子"型超材料单元加载于同轴馈电微带天线的正上方,利用其零折射率效应聚拢电磁波;将π型超材料单元加载于天线基板,利用超材料的禁带效应抑制天线后向波。分别对两种优化方法进行实验对比分析,最后综合两种方法设计出一款高方向性、高增益的微带天线。结合仿真实验与实物测试结果验证了理论的正确性。综合设计的新型微带天线与传统天线相比,增益为8.94 d B,增加了3.03 d B,提高了51.27%,方向性系数为10.69 d B,增加了3.51 d B,提高了48.89%,达到了设计实验的目标。     

使用遗传算法简化设计矩形微带天线

讨论了矩形微带天线的传输线模型、遗传算法的编码方式、适应度函数的设计等,提出了一种利用遗传算法优化结果设计矩形微带天线的方法.利用反射系数,设计了简单的适应度函数,采用小规模的初始种群,加速了程序的收敛速度.仿真结果表明,遗传算法优化设计微带天线,可使反射系数小于-25 dB、增益大于5.5 dB.     

基于各向异性混合介质近零折射率超材料的高增益微带天线

根据斯涅尔定律,透过近零折射率超材料(Near Zero Index Metamaterials,NZIM)的电磁波会变为垂直于超材料表面的高指向性波束。这种特性使NZIM材料被广泛应用于高增益及高定向性天线设计中。基于此,设计一款基于各向异性混合介质近零折射率超材料的高增益微带天线。混合介质超材料单元由F₄BM介质及高纯度铜导体组成。根据金属等离子体理论,金属阵列等离子体频率与入射波谐振频率相近时,会呈现近零介电常数。通过合理调节金属半径及介质单元周期,最终使该混合介质在9.5～10.2 GHz频段内折射率近零且等效阻抗接近1,能够与空气匹配。对基于混合介质超材料的微带天线进行加工测试,结果表明,加载混合介质覆层后,微带天线增益明显提高,最大增益提高4.1 dB。     

加载人工电磁结构的高增益耐高温天线设计北大核心CSCD

本文设计了一款加载人工电磁结构的耐高温天线，为实现弹载天线共形后增益的提高，采用微带天线加载近零折射率材料层方式实现增益提高。通过在天线外部覆盖天线罩形式实现隔热功能，可实现在罩的上表面持续350℃加热时，实现120s内馈电端口处温度小于100℃。首先设计了一款工作在35GHz处的微带天线，实现最大增益为8dBi，其次通过加载两层近零折射率材料和加天线罩所需地板对电磁波的反射，实现天线增益提高到15.4dBi，远高于单个微带天线增益。后期进行了加工与实测，常温实测结果天线最大增益达到14.5dBi左右，E面和H面波束宽度约在24°左右，实测结果与仿真结果差别不大，不仅实现了对单个微带天线增益的较大提升；而且高温隔热性能满足要求。     

一种基于超材料的小型化宽带微带天线

分别将创新设计的“四方形”超材料单元和周期条形缝隙蚀刻在普通微带天线的辐射贴片和接地板上,设计了工作在3.67~14.17 GHz 的一种小型化宽带高增益微带天线。与原始的天线相比,新型天线的谐振中心频率降低了44.8%,相对带宽从2.7%扩展到243.1%,同时保持了良好的增益。实物测试结果与仿真结果吻合较好。因为超材料的左手传输特性影响了微带天线介质基板的等效媒质参数,导致天线的辐射场主要集中在水平方向,而不是传统的微带天线的垂直方向。     

C波段超材料基板高增益微带天线

针对普通微带天线增益较低的缺点,在普通微带天线上引入带有双面树枝状结构的新型负磁导率材料作为天线的基板,设计了中心工作频率为5.28 GHz的微带天线,对此天线的性能进行了研究.结果表明,通过引入负磁导率材料,天线的性能有了显著的改善,侧向辐射减弱,前向辐射增强,相对于普通微带天线,负磁导率材料微带天线的增益最大提高了2.47 dB,E面方向图的半功率波束宽度收缩了21.93°.     

基于Polys try介质基板微带天线的应用研究

针对传统贴片天线检测频率有限(2~35 GHz)且由于增益低导致检测结果不明显的问题,文中提出了以聚苯乙烯作为介质基板构建微带天线的解决方案。在以介电材料玻璃超细纤维为介质基板的理论基础上,采用高分子材料Polysty作为介质基板构建微带天线模型。结合经典天线理论计算辐射贴片以及介质基板尺寸;基于HFSS搭建Polysty作为介质基板的模型并根据微带天线特性将理论设计的微带天线参数进行优化,最终得到在1 GHz时微带天线的最佳尺寸。仿真及实验结果表明,Polysty作为介质基板的微带天线中心频率可以达到1 GHz,增益高并且检测角度范围大。     

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。     

遗传算法在优化设计宽频微带天线中的应用

将遗传算法与FDTD法结合优化设计出了一种宽频微带天线.文中简要讨论了遗传算法的操作过程,并介绍了减少遗传算法与FDTD法结合优化微带天线计算量的方法.与初始矩形微带天线相比,优化后天线的阻抗带宽增加了三倍多.     

Shape optimisation of broadband microstrip antennas using geneticalgorithm

The genetic algorithm (GA) is used to design patch shapes for microstrip antennas on FR-4 substrate for broadband applications. Measurement results of the GA-optimised designs show good agreement with numerical prediction. The optimised patch design achieves a fourfold improvement in bandwidth when contrasted with a standard square microstrip antenna     

Performance enhancement of rectangular microstrip patch antenna using double H shaped metamaterial

In this paper a high performance rectangular microstrip patch antenna (RMPA) has been designed using doubleHshaped metamaterial. First, the doubleHshaped metamaterial has been designed and optimized at 5.2 GHz resonant frequency of patch antenna. It has been found that embedding of this metamaterial into the substrate beneath the reference patch antenna improves its return loss and bandwidth without changing the resonant frequency and gain. To further enhance the gain and efficiency of the metamaterial embedded RMPA a superstrate of double H shaped metamaterial has been applied at the distance of -/3 over it. Finally, a high gain, broadband and good impedance matched metamaterial inspired RMPA has been obtained. The proposed antenna was simulated and optimized using HFSS software. The prototype antenna has been fabricated and measured results of the proposed antenna are found to be in good agreement with the simulated results.     

Compact circularly polarised microstrip antenna with slotted groundplane

A novel compact circularly polarised microstrip antenna with a slotted ground plane is proposed. By embedding a group of four bent slots in the ground plane and truncating a pair of patch comers in the radiating square patch, the proposed antenna can perform circular polarisation (CP) operation with a reduced antenna size at a fixed operating frequency. In addition, enhanced CP bandwidth and antenna gain for the proposed design are observed. Details of the antenna design and experimental results are presented and discussed     

Compact and miniaturized microstrip antenna based on fractal and metamaterial loads with reconfigurable qualification

We have described a compact antenna based on fractal and metamaterial loads techniques. The microstrip patch antenna is assumed as a basic antenna and then the effect of fractal structures is implemented. The fractal patch is considered as a right-handed element and then by adding a left-handed element, the antenna miniaturization is achieved by using the metamaterial loads technique. The equivalent circuit is also used to describe the element effect on miniaturization and parametric models clarify them. The proposed antenna is modified for wireless applications and experimental results confirm our simulation results. In addition, we show that the proposed antenna is suitable for reconfigurable. By joining the unit cells together with various arrangements and changing the effective length, the various inductances can be obtained. Finally, by adding reconfigurable characteristic to the proposed antenna, the gain and radiation pattern can be controlled as shows in this paper. The patch antenna has low bandwidth and gain and so we have developed the patch antenna with defected ground to improve the bandwidth and the Frequency Selective Surface (FSS) is used to achieve higher gain and bandwidth. The final antenna is covering 2.4, 3.5 and 5.5 GHz with higher gain than the patch antenna.     

Dual band microstrip patch antenna array loaded with split ring resonators and via holes

Reduction in antenna size by using multi-band radiators play a vital role in the miniaturization of present world wireless handheld devices, as dual band behaviour of the antennas result in the integration of more than one communication standard in a single system and thus, saving the installation space required for separate antennas. In this context, this communication presents a shorted-pin dual band metamaterial inspired microstrip patch antenna array. Under the unloaded conditions, the traditional patch antenna array resonates at 5.8 GHz with gain of 9.8 dBi and bandwidth of 540 MHz. However, when each patch of this traditional antenna array is loaded with split ring resonator (SRR) and a metallic via hole is introduced in the patch, the same antenna array produces an additional resonant frequency in IEEE 802.11b/g/n 2.45 GHz Wi-Fi band with bandwidth and gain of 290 MHz and 5.6 dBi, respectively, while the initial resonant frequency (i.e. 5.8 GHz) gets shifted to IEEE 802.11ac 5 GHz Wi-Fi band, providing the gain and bandwidth of 11.4 dBi and 510 MHz, respectively. The proposed antenna array has been fabricated, and the measured results are presented to validate the proposed array. Moreover, the equivalent circuit of the proposed antenna array has been designed and analyzed to validate the simulated, measured and theoretical results. Attainment of dual band characteristics by incorporating the metamaterial with single band traditional patch antenna array makes this structure novel, as this has been achieved without any extra hardware cost, size and loss of structural planarity. Also, both the frequency bands of this proposed metamaterial inspired antenna array possess considerable gain and bandwidth.     

Single-feed square-ring microstrip antenna with truncated cornersfor compact circular polarisation operation

A novel circular polarisation (CP) design of a single-feed square ring microstrip antenna with truncated corners is described. Experimental results show that the proposed design has a reduced antenna size as compared to the conventional circularly-polarised square microstrip antenna with truncated corners at a given operating frequency. Also, the required size of the truncated corners for CP operation is larger for the present design than for the conventional design using a square microstrip patch, which suggests that the fabrication tolerance is relaxed for the present design. Typical results are presented and analysed     

High gain multiband and frequency reconfigurable metamaterial superstrate microstrip patch antenna for C/X/Ku-band wireless network applications

Wireless Networks - We present a metamaterial superstrate based microstrip patch antenna with PIN diode switches applicable for wireless network applications. Metamaterials in the form of square...