Optimization of a buried microstrip antenna for simultaneous communication and sensing of soil moisture

Imbedded microstrip antennas have been previously demonstrated for use either as sensing elements or as components of a wireless communication system. This paper presents a method and dual use designs for simultaneous sensing of soil moisture and communication from the buried antenna to an external receiver. Using the genetic algorithm and the finite-difference time domain (FDTD) method, the sensing band is designed to have maximum sensitivity to the moisture of the surrounding soil, while the communication band is designed to have minimal detuning due to changes in soil moisture. Single layer and stacked microstrip antennas are shown.     

一种提高微带MIMO 天线端口隔离度的新方法

多输入多输出(MIMO) 无线通信系统已经成为提高通信系统可靠性和数据传输速率的有效技术。MIMO 通信系统中,终端天线的性能对系统通信容量的提升至关重要。为了提高天线端口隔离度,提出了一种在微带天线辐射贴片上加载缝隙阵列实现天线极化分集,提高天线隔离度的方法,并且将这种方法应用于两个2 单元微带MIMO 天线设计中,取得了良好的效果。缝隙阵列加载不但抑制了微带MIMO 天线单元间的耦合,而且产生了更多谐振频点,改善了高频谐振频点畸变的天线辐射方向图,并且天线尺寸也得到了很大的减缩。最后对比分析了设计的两个微带MIMO 天线,实测结果与仿真计算比较可知,在工作带宽内,单元天线间耦合得到了非常有效的抑制。这种在平面天线辐射贴片加载缝隙阵列改变天线极化方向的技术可以很好地用来抑制多天线系统中单元天线间的耦合,而且对天线的其他性能不会造成影响。     

E-shaped patch antennas for high-speed wireless networks

Thin, broad-band, E-shaped microstrip patch antennas (ESPAs), operating in the 5-6 GHz frequency range, are presented. They are intended for high-speed (IEEE 802.11a, 54 Mb/s) wireless computer local area networks (WLAN) and other wireless communication systems. They are suitable for WLAN adaptor cards in the PCMCIA (also known as PC) format, allowing users of current notebook computers to upgrade to this high-speed wireless standard at a low cost. Importantly, our antennas are thin enough to be accommodated in a PCMCIA card of standard 5-mm thickness, without making the antenna end thicker than the card itself. Two different closely spaced antenna pairs are also presented for diversity. A new ESPA configuration with a microstrip feed is presented for easy integration with microwave transceivers. In all cases, within the two IEEE 802.11a WLAN bands (5.15-5.35 GHz and 5.725-5.825 GHz), the reflection coefficient at the antenna input is <-10 dB and in both antenna pairs, mutual coupling between the two antennas is <-20 dB.     

Patch antennas with switchable slots (PASS) in wireless communications: concepts, designs, and applications

This feature article describes, in a comprehensive and unified fashion, the authors' work on the development of novel kinds of reconfigurable microstrip antennas: patch antennas with switchable slots (PASS). PASS are versatile for wireless communication systems, and their structure is very simple. This article introduces the operational mechanism of PASS, as well as their frequency-ratio control and input impedance tuning. Various PASS designs are presented to demonstrate the capability of PASS in wireless communication. These designs demonstrate the functions of dual-frequency operation, dual-band circular-polarization performance, and circular-polarization diversity with only one layer and a single feed. A practical PASS application for future Mars rover missions is also highlighted: a compact, dual-band, circularly polarized antenna for the UHF band was designed, fabricated, and measured, based on the PASS concept.     

微带磁流振子天线综述

文章综述了微带磁流振子天线的最新发展情况,从理论上对比了微带磁流振子天线和电流振子天线的辐射机理,阐述了微带磁流振子具有水平极化和高增益的新颖性,最后介绍了微带磁流振子在新型天线阵列、圆极化天线、高增益天线的应用。     

Dual-band printed dipole antenna with parasitic element for WiMAX applications

Recently, wireless communication has grown exponentially worldwide. The wireless system that is currently popular is the Worldwide Interoperability for Microwave Access (WiMAX) system, which operates in the 2.5?2.7, 3.3?3.8 and 5.2?5.8 GHz frequency bands; the standard that defines interoperability across these bands is IEEE 802.16a/d/e/2004 [1]. Because of this, broadband and multiband antenna designs have become important in wireless applications. Recently, various antenna designs such as those of microstrip line, coplanar waveguide, and PIFA dipole antennas have been presented in the literature. In [2], a novel miniature end-loaded planar open-sleeve dipole (ELPOSD) antenna was presented; it was demonstrated to have a large bandwidth and a short length. A printed dipole antenna with U-slotted arms was proposed in [3]. With the aid of an embedded U-shaped slot, it can generate a new resonant mode at 5.2 GHz. In [4, 5], printed dipole and monopole antennas with parasitic elements were presented. The experimental results show that parasitic strips can be coupled with dipole antennas in order to give rise to additional resonance modes. A broadband printed dipole antenna with a stepshaped feed gap was proposed in [6]. The wide operating band is controlled by the different lengths of the radiation arms. Thus, it was demonstrated that a dipole antenna with parasitic elements has the ability to realise multiband or broadband operation.     

Microstrip antennas

Microstrip antennas have been one of the most innovative topics in antenna theory and design in recent years, and are increasingly finding application in a wide range of modern microwave systems. This paper begins with a brief overview of the basic characteristics of microstrip antennas, and then concentrates on the most significant developments in microstrip antenna technology that have been made in the last several years. Emphasis is on new antenna configurations for improved electrical performance and manufacturability and on advances in the analytical modeling of microstrip antennas and arrays     

Multiband Printed Monopole Slot Antenna for WWAN Operation in the Laptop Computer

A multiband printed monopole slot antenna promising for operating as an internal antenna in the thin-profile laptop computer for wireless wide area network (WWAN) operation is presented. The proposed antenna is formed by three monopole slots operated at their quarter-wavelength modes and arranged in a compact planar configuration. A step-shaped microstrip feedline is applied to excite the three monopole slots at their respective optimal feeding position, and two wide operating bands at about 900 and 1900 MHz are obtained for the antenna to cover all the five operating bands of GSM850/900/1800/1900/UMTS for WWAN operation. The antenna is easily printed on a small-size FR4 substrate and shows a length of 60 mm only and a height of 12 mm when mounted at the top edge of the system ground plane or supporting metal frame of the laptop display. Details of the proposed antenna are presented and studied.      

Radiation and scattering characteristics of microstrip antennas onnormally biased ferrite substrates

Radiation and scattering characteristics of microstrip antennas and arrays printed on ferrite substrates with a normal magnetic bias field are described. The extra degree of freedom offered by the biased ferrite can be used to obtain a number of novel characteristics, including switchable and tunable circularly polarized radiation from a microstrip antenna having a single feed point, dynamic wide-angle impedance matching for phased arrays of microstrip antennas, and a switchable radar cross section reduction technique for microstrip antennas. Results are obtained from full-wave moment method solutions for single microstrip antennas and infinite arrays of microstrip antennas. A cavity model solution for a circular patch antenna on a biased ferrite substrate is also presented, to aid in understanding the operation of these antennas     

Miniaturization of an Ultra‐Wideband Antenna with Two Spiral Elements

In this letter, novel antennas with two spiral elements are presented for ultra‐wideband application. The original antenna consists of a T‐shaped microstrip feed line, two spiral radiating elements, and a ground plane with two circular slots. It measures 30 mm × 40 mm × 1.6 mm. Spiral elements are used to increase the lower bandwidth limit. To further reduce the size of the antenna, the original antenna is cut in half by using the symmetry of the surface current distributions. The proposed antennas feature omnidirectional radiation patterns and good gain flatness.     

Design of wideband circularly polarized aperture-coupled microstripantennas

Two variations of a novel feeding technique for a wideband circularly polarized aperture-coupled microstrip antenna are described. Prototype designs for wideband linearly polarized elements are first presented, and then used for circularly polarized designs. Techniques used for design of the feed network are detailed, for both series feed and parallel feed versions. Experimental results are shown for each antenna, and results for the two designs are compared. The impedance and axial ratio bandwidths for these antennas are among the best yet achieved for microstrip antenna elements. Several design variations are also discussed     

基于遗传算法的微带天线优化

微带天线具有质量轻、体积小和易于制造等优点,已广泛应用于个人无线通信中。文中将遗传算法和HFSS-Matlab-API接口程序应用到微带天线优化中,设计了一套基于遗传算法和HFSS的天线优化方案。针对微带天线带宽窄的缺点,成功利用该方案优化出了一种宽带E形微带天线的尺寸以及馈电位置,带宽由一般微带天线约5%展宽到30%左右。     

Directional reconfigurable antennas on laptop computers: Simulation, measurement and evaluation of candidate integration positions

This study reports on the integration of a novel reconfigurable microstrip antenna capable of reconfiguring both its radiation pattern and frequency response onto a generic laptop computer structure. The purpose of such an exercise is to provide the relevant information necessary to integrate high performance antennas onto structures that can be used in ad hoc communication scenarios as well as other demanding applications. To pre-evaluate candidate antenna locations on the laptop chassis, an electromagnetic visibility study (EVS) is performed. Once integrated into candidate positions that have been analyzed by the EVS, the operation of the antenna on the host structure is measured and assessed with consideration to several realistic electromagnetic environments. The resulting performance and packaging issues are discussed. A formalized procedure for the integration of the antenna onto any host chassis using the EVS as a tool is also included.     

Center-fed microstrip patch antenna

A novel feeding scheme for microstrip patch antennas is presented, which consists of a coaxial probe and shorting pin separated by a narrow slot centrally cut at the radiating patch. The impedance and radiation characteristics of a conventional probe-fed microstrip patch antenna and the proposed microstrip patch antenna are experimentally examined and compared. The effects of the slot length on the antenna operation are also discussed.     

Smart antennas

Smart antennas have received increasing interest for improving the performance of wireless radio systems. These systems of antennas include a large number of techniques that attempt to enhance the received signal, suppress all interfering signals, and increase capacity, in general. The main purpose of this article is to provide an overview of the current state of research in the area of smart antennas, and to describe how they can be used in wireless systems. Thus, this article provides a basic model for determining the angle of arrival for incoming signals, the appropriate antenna beamforming, and the adaptive algorithms that are currently used for array processing. Moreover, it is shown how smart antennas, with spatial processing, can provide substantial additional improvement when used with TDMA and CDMA digital-communication systems. The material presented is tutorial in nature, leaving the details for further study from the papers appearing in the reference list     

Broadband quasi-microstrip antenna

A new printed microwave antenna is presented. The antenna is a hybrid between a wire antenna array and a microstrip patch antenna. Although the size, cost, and efficiency are comparable to the microstrip patch, the voltage standing wave ratio 2:1 bandwidth of the antenna presented here is above 20%. The radiation pattern of the antenna does not change appreciably within the bandwidth, and the theoretical efficiency for optimal antennas remains above approximately 80% within the bandwidth. Measurements on several antennas around 2 and 4 GHz are presented, as well as theoretical results obtained using a full-wave analysis     

Multiport scattering analysis of general multilayered printedantennas fed by multiple feed ports. I. Theory

A general solution is given for a class of printed antenna geometries composed of multiple dielectric layers or ground planes, radiating patches, dipoles, or slots, and an arbitrary configuration of multiple transmission lines proximity-coupled or aperture-coupled to the radiating elements. The solution uses a full-wave spectral-domain moment method approach, and a new generalized multiport scattering formulation to model the excitation from the multiple feed lines. This method treats infinite phased arrays as well as isolated elements. The general theory using the new multiport scattering formulation is elaborated, with details of the key analytical and numerical aspects. Considering the unified nature of the multiport scattering analysis, and its simplicity, this analysis is appropriate for computer simulation of a large variety of multilayered microstrip antennas involving radome layers, dual polarized feeds, proximity-coupled or aperture-coupled elements, multifeed stacked or parasitic patches, and several related configurations for integrated phased array applications     

有源微带天线阵列的实验研究

本文提出了一种混和集成型有源阵列天线结构，并对这一结构进行了空间功率合成的实验研究。功率源采用微带型振荡电路；天线采用矩形微带贴片阵列，二者通过背馈相连。贴片天线阵间的互耦使振荡单元间实现注入镇定，各单元的辐射功率在空间实现合成。在Ｘ波段成功地实现了四单元有源阵列的互锁和空间功率合成。本文报导了实验结果并给出了一些有意义的结论     

共面耦合馈电小型化E-E形及半E-E形宽带微带天线

提出并设计了一种可应用于多频段无线通信的小型化宽带微带贴片天线.天线采用共面容性耦合的馈电方式补偿探针的分布电感,应用FR4高频介质板与空气层组成的层叠介质、E-E形和半E-E形辐射贴片缩减天线的尺寸.结果表明,E-E形微带天线和半E-E形微带天线的阻抗带宽分别为1.85～2.57 GHz(相对带宽32.6％)和1.85～2.50 GHz(相对带宽29.9％).和普通E形微带天线相比,E-E形和半E-E形微带天线的贴片面积缩小了47％和61％.     

Optimization of Circular Ring Microstrip Antenna Using Genetic Algorithm

Circular ring microstrip antennas have several interesting properties that make it attractive in wireless applications. Although several analysis techniques such as cavity model, generalized transmission line model, Fourier-Hankel transform domain and the method of matched asymptotic expansion have been studied by researchers, there is no efficient design tool that has been incorporated with a suitable optimization algorithm. In this paper, the cavity model analysis along with the genetic optimization algorithm is presented for the design of circular ring microstrip antennas. The method studied here is based on the well-known cavity model and the optimization of the dimensions and feed point location of the circular ring antenna is performed via the genetic optimization algorithm, to achieve an acceptable antenna operation around a desired resonance frequency. The antennas designed by this efficient design procedure were realized experimentally, and the results are compared. In addition, these results are also compared to the results obtained by the commercial electromagnetic simulation tool, the FEM based software, HFSS by ANSOFT.