Comparative study on directional sensitivity of patch‐antenna‐based strain sensors

In this article, we present a comparative study into the directional sensitivity of patch‐antenna‐based strain sensors. Two linearly‐polarized (LP) patch sensors vs a circularly‐polarized (CP) patch sensor with identical configurations are demonstrated. The strain occurred in real structures is commonly uncertain, the usefulness of LP‐patch sensor becomes limited. Like the conventional strain gauges, it can only be used if the strain direction is known beforehand. Therefore, a nearly‐square CP‐patch sensor for multi‐directional strain monitoring is proposed here. In order to obtain high sensitivity, three novel strain sensing methods are proposed for strain monitoring. Multi‐directional strain sensing is achieved by a proof‐of‐concept prototype. The simulated results verified by experimental results show that high sensitivities of these three methods were achieved.     

基于k平面对圆极化微带天线馈源的确定

微带天线馈点的位置决定天线辐射波的模式和天线与馈线的匹配情况。本文以矩形微带天线形成圆极化波为研究对象,利用k平面相位关系,从理论上推导其馈电点的轨迹方程,通过编程确定其具体的馈电点,利用HFSS9.2仿真观察其S11曲线。     

Resonant frequency of a microstrip patch in the vicinity of an identical radiator

The resonant frequency of a microstrip patch (rectangular, square, and circular) changes as soon as an identical patch is brought closer than 0.2λ to it. Closed-form expressions are presented for the H-plane-coupled configuration (the two adjacent patches are excited by same phase excitation) from which this altered resonant frequency may be easily computed. From the same expression the resonant frequency of an isolated patch antenna may also be calculated. A procedure utilizing these closed-form expressions for the design of microstrip patch antennas which will resonate at the desired frequency is also outlined. These expressions may be readily used in the computer-aided design of microstrip antenna arrays. © 1996 John Wiley & Sons, Inc.     

宽带圆极化阵列天线设计

提出了一种应用于S波段小型宽带圆极化微带贴片天线阵列。单点背馈式方形贴片印刷于Duroid5880介质板上,在贴片上加载两个相邻矩形缝隙,一方面实现圆极化辐射,另一方面拓展天线单元的阻抗带宽。利用该单元组阵,通过采用连续相位旋转法馈电天线单元拓展天线阵列的轴比带宽,仿真结果表明,线阵和面阵的阻抗和轴比带宽均达到10%以上。     

宽频带高增益RFID微带天线阵设计

设计了一种宽频带高增益微带天线单元并组成了4元阵列。通过在普通矩形微带贴片加载2个对称切角、改变贴片表面电流分布实现天线单元的双频工作,调节切角尺寸使两个频点相互靠近融合,展宽频带。在此基础上确定合适的阵元间距,采用等副同向并联馈电,馈电网络由T型结功分器组成,并使用同轴探针馈电方式,实现天线阵列的设计。通过高频电磁结构仿真软件HFSS对天线进行仿真和优化,结果表明阵列天线性能良好。     

A novel dual‐wideband inscribed hexagonal fractal slotted microstrip antenna for C‐ and X‐band applications

This paper presents a novel geometry of inscribed hexagonal slotted microstrip antenna for dual‐band performance where the fractal iteration has been made by introducing concentric slots in the patch geometry. Using the equivalence principle and cavity model, the basic geometry of the hexagonal slotted patch is analyzed, and the resonant frequencies of different modes of the patch are computed. Higher‐order modes of the patch antenna are used to obtain dual band. Good performance in terms of the reflection coefficient is proved with the help of parametric analysis. The antenna geometry is simulated using electromagnetic simulation software based on the finite‐element method. The prototype of this antenna is fabricated and tested. The practical results match with the simulated results. The proposed antenna provides improved average gain. The peak values of measured gain are found to be 5.238 and 7.023 dBi—in the two bands 5.85 to 6.48 GHz and 7.28 to 8.63 GHz, respectively. Stable radiation patterns with good average gain make the proposed antenna appropriate for long‐range transmission. Furthermore, low profile and low cost make this antenna suitable for the future point‐to‐point high‐speed wireless communication applications.     

Low profile coupling feed circularly polarized antennas for WLAN applications

This article presents two designs of circularly polarized antenna with simple circular‐shaped radiator and circular slotted ground plane. An arc‐shaped microstrip line coupling feed mechanism is used to excite the circular radiating patch. The 3‐dB axial ratio bandwidth of the proposed antenna‐1 and proposed antenna‐2 are 3.33% and 18%, respectively. The proposed design has several advantages such as easy matching, fabrication simplicity, compact size, and wide axial ratio bandwidth. Both the antennas have been designed on FR‐4 substrate with dielectric constant 4.4 and thickness 1.59 mm. Simulated and measured results are presented to validate the working of the proposed antennas.     

High isolation dual‐frequency patch antenna integrated with cascade defected microstrip structure

This article presents a high‐isolation dual‐frequency rectangular patch antenna utilizing microstrip feed line integrated with a cascade defected microstrip structure (CDMS). Two types of CDMS are added, T‐shaped CDMS and Dumbbell‐T‐shaped CDMS. Simulation results show using these structures improve isolation up to 70 dB and reduce harmonic signals from transmitter. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

一种应用于微波探测的双频天线的设计

为增加火灾探测天线频带范围,基于微带贴片天线,采用凹槽加载技术,设计了中心频率在Ku(12.4～18.0 GHz)波段的双频微带单元天线.利用HFSS软件对其建模、仿真及优化,结果表明,该单元天线在14.8 GHz和16.1 GHz时回波损失达到最小值,且回波损失小于-10 dB的带宽分别为600MHz和390 MHz.利用该单元天线,进而设计了一款2×2阵列天线,实测结果表明:该阵列天线具有很好的双频谐振特性,在14.3～14.9 GHz和15.7 ～16.1 GHz频带内既保留了原单元天线好的回波损耗特性,又提高了增益,使两个频段最大增益分别达到13.7 dBi和11.3 dBi.     

星载合成孔径雷达双极化天线阵研究

介绍了一种宽带双极化星载SAR有源相控阵天线阵,该天线以TR组件和双极化线阵组成的有源线阵为基础,并根据相控阵天线对雷达信号瞬时带宽的限制条件,选择合适的实时延迟子阵,结合结构安装的要求,构成电气独立的模块。在此基础上,根据雷达对天线孔径大小的需要,通过馈电网络激励拓展成大型有源相控阵天线,该天线可以通过波控灵活的控制和网络的合成,实现多极化、波束扫描、波束赋形和多通道等功能。其中对于双极化辐射天线,分别针对微带贴片天线阵和波导缝隙天线进行了分析和研究,并给出了实验验证结果。微带天线阵采用宽带的双层贴片辐射单元和并馈网络实现大带宽要求,两种正交极化模式分别由共面微带线和缝隙耦合来激励,其馈电网络居于开有耦合缝隙接地板的两侧,实现复杂网络空间安排和降低馈线耦合的功能。对于贴片单元的激励,采用对称、反相馈电和分组优化等方法,有效地提高了极化隔离度和极化纯度;而双极化波导缝隙阵中,以脊波导宽边纵缝谐振阵实现垂直极化,波导窄边非倾斜缝隙阵实现水平极化,在每种线阵中都通过分组馈电、过载技术和辐射/馈电波导一体化设计,实现了宽带和压缩横截面的目的。两种形式的天线阵比较,阵面剖面高度相当,微带阵具有宽带、轻质、易于加工和成本低等优势,而波导缝隙阵则具有高效、高隔离度和低交叉极化等性能,但是其缺点是结构复杂、加工难度大和重量大等。     

基于双三角形谐振环结构左手材料的矩形微带贴片天线

设计了一种双三角形谐振环结构的左手材料,通过理论计算和仿真实验证明了其具有电磁左手材料性质;将双三角形谐振环结构的左手材料加载在矩形贴片微带天线上,并给出了矩形微带贴片天线的结构参数;利用HFSS仿真软件对比了加载左手材料前后矩形贴片微带天线的性能,仿真结果表明,左手材料的加载提高了天线的带宽,增大了天线的增益,有效地抑制了旁瓣。     

平面电容传感器设计及在材料探伤中的应用研究

材料内部不同损伤具有不同的介电特性,利用平面电容传感器可以实现无损检测。平面电容传感器电极位于同一平面,敏感场非均匀分布,电极结构是影响传感器敏感场分布的主要因素。研究敏感场分布特性有助于提高传感器测量精度。本文基于有限元研究了不同电极结构的平面电容传感器,仿真结果表明,矩形叉指电极敏感场分布均匀性好。分别优化矩形叉指电极和圆形电极结构参数,并基于PCB工艺研制传感器用于材料损伤检测。实验验证了平面电容传感器用于材料探伤的有效性,且矩形叉指电极传感器测量效果优于圆形电极。     

Radio frequency response of flexible microstrip patch antennas under compressive and bending loads using multiphysics modeling approach

This research article studies the effect of compression and bending loads on resonant frequency of microstrip patch antennas using COMSOL Multiphysics software (will be called COMSOL hereafter). In this study, copper microstrip patch antenna of dimension 30 mm × 25 mm on polydimethylsiloxane (PDMS) substrate of dimension 50 mm × 50 mm is considered. The interface bonding is assumed to be ideal between the patch and substrate. Both Ansoft HFSS and COMSOL are used to model and analyze the original geometry of the microstrip patch antenna without applying physical load to make sure that the design and the impedance match is satisfactory. Then, COMSOL is used to find deformed shape of the microstrip patch antenna under different values of compression and bending loads. The deformed geometries are reanalyzed using COMSOL radio frequency (RF) simulation. The resonant frequencies at different load levels are obtained and the effect of loading and boundary conditions on the resonant frequency shift is discussed.     

Serial‐feed for a circular patch antenna with circular polarization suitable for arrays

A compact sequential‐rotation array with serial feed and three probes using multi‐layer substrate is proposed. The most compact shape for the microstrip patches are selected with the optimization for the axial ratio and return loss bandwidth. The gain, return loss, and axial ratio bandwidths of the antenna are improved significantly by converting three patches to one circular. The patch radius and the position of probes are selected to form circular Poynting vectors around it where the maximum power is present at large frequency range. While the two layers of the structure use similar board this structure only uses a substrate and three simple pins. Also the total area of the antenna is limited to the microstrip patch and it has a straightforward fabrication steps. So the wideband antenna is relatively inexpensive and compact. The antenna has 21.4% 3 dB axial ratio bandwidth in simulation and 21.1% in fabrication. Consequently, the serial‐multi‐fed circular patch with unique angular and phase arrangements is suitable for many applications as the antenna arrays. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:529–535, 2014.     

一种矩形微带整流天线的研究与设计

微波整流是无线输电中的一个重要环节,为完成微波能量的接收,设计了一个结构简单、整流效率高的贴片矩形微带整流天线,此整流天线包括矩形微带天线、输入低通滤波器、整流二极管及输出滤波器。该整流天线的面积小,配合其他装置组成的微波输电系统,可方便地应用于传统有线输电无法应用的场合。通过系统仿真以及实验测试,验证了整流天线的可行性及其高效率,实际测量后计算出整流效率高达63．4％。     

Microstrip tapered traveling wave antenna for wide range of beam scanning in X‐ and Ku‐bands

In this work, a broadband traveling wave antenna (TWA) is presented as a microstrip design that is capable of a wide range of beam scanning by changing the operation frequency within 8 to 14 GHz. For this purpose, a rhombus shaped microstrip patch is used as a unit element and TWA is built as a tapered microstrip line consisting of the cascaded rhombus shaped unit elements and terminated by a rectangular antenna instead of traditional resistive termination which can be called patch loaded traveling wave antenna (PLTWA). Optimization and simulation of the PLTWA is carried out using 3‐D Microwave simulation software CST and its dimensions are resulted as 130 × 30 mm. From the simulations, it should be noted that the patch termination increases the maximum gain almost 3 dB and the total efficiency up to 90% compared to the traditional resistive load over the operation band at the expanse of a small distortion on S₁₁ characteristics. Then the PLTWA is fabricated and measured along its operation band 8 to 14 GHz and it exhibits a peak gain of 9.5 dBi at 11 GHz. The measured gain of the proposed antenna is found between 9 dB and 12 dB and its beam direction is steerable with the range of 80° (?65°‐15°) over the operation band 8 to 14°GHz.     

Bacterial foraging optimization technique to calculate resonant frequency of rectangular microstrip antenna

Resonant frequency of rectangular microstrip antenna having various substrate thicknesses are generally calculated using the standard expressions presented in literatures. But these equations suffer from errors when compared with the experimental values due to Quasi‐TEM propagation in the microstrip structure and fringing field. A number of researchers used soft computing approach such as neural networks and genetic algorithm on those equations to minimize the error for better accuracy. Bacterial foraging, an evolutionary optimization technique conceived in recent times, has many advantages over genetic algorithm and is yet to be applied on the design of microstrip patch antenna. In this article, a novel technique is developed to apply bacterial foraging optimization technique in conjunction with the expressions developed to calculate accurately the resonant frequency of rectangular microstrip antenna of any dimension and of any substrate thickness. Further, bacterial foraging is applied to the calculatation of the feed point of microstrip antenna. The technique developed in this article can be a generalized soft computing tool to calculate resonant frequency of rectangular microstrip antenna. Similarly, the idea of the article can be used for calculating the various parameters of microstrip antennas of different structure and geometry. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.     

Analysis of one wide‐band and high gain patch microstrip antenna using the FDTD method

We present results of a recent investigation into a wide‐band and high gain patch microstrip antenna using the finite‐difference time‐domain (FDTD) method. The substrate–superstrate resonance technique was used to increase the antenna element gain. An aperture‐coupled rectangular patch microstrip antenna with two superstrate layers was designed, and the effect of the finite ground plane on the gain of the antenna element was analyzed. The antenna was fabricated and tested. The measured results are presented in comparison with the simulated ones. ©1999 John Wiley & Sons, Inc. Int J RF and Microwave CAE 9: 468–473, 1999     

Substrate fields modulation with defected ground structure: A key to realize high gain,wideband microstrip antenna with improved polarization purity in principal and diagonal planes

Rectangular microstrip patch antenna with circular headed dumbbell shaped defect in ground plane has been studied experimentally for concurrent improvement in its gain, bandwidth and polarization purity in principal and 45° diagonal planes. Around 9–9.5 dBi peak co polarized (CP) gain, 22% impedance bandwidth along with minimum 19–20 dB of CP‐cross polarized (XP) isolation in both principal and 45° diagonal plane are achieved with the present structure. These observed improvements in results from present antenna are justified with physical insight. The present structure is simple and easy to manufacture. The geometry of the defect in ground plane has been shaped judiciously to modulate the fields beneath the patch efficiently for simultaneous improvement of the three parameters. Very close mutual agreement between simulation and measure results are revealed. The present investigation provides an insightful, visualization‐based understanding of concurrent improvement of all these parameters. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:174–181, 2016.     

Microstrip‐fed cusp antenna for ultra‐wide band communication systems

A novel antenna for ultra‐wideband (UWB) applications is presented in this article. The proposed antenna consists of one circular patch placed on one side of a substrate and one circular slot placed on the other side. The antenna is fed with a microstrip line connected to the circular patch. The radii of the circular patch and slot and the separation between their edges represent the three design parameters which are optimized such that the antenna satisfies the design specifications. The proposed antenna has been fabricated using printed circuit board (PCB) technology. It has been characterized both theoretically and experimentally. The measured and calculated results are presented, compared, and discussed. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.