Design of a loaded monopole having hemispherical coverage using agenetic algorithm

A genetic algorithm is used to design a monopole loaded with a modified folded dipole so that it radiates uniform power over the hemisphere. Each of the wires that make up the antenna are given a range of possible lengths. The genetic algorithm randomly selects a sample population of possible antenna configurations from the total population of all configurations. The radiation pattern of each sample configuration is computed using the numerical electromagnetics code (NEC). The solutions are compared with the desired pattern and ranked in terms of performance. The best solutions are retained and mated with one another and the process is repeated until an optimal solution is obtained. The genetic algorithm quickly produced an antenna that has a nearly uniform power over the hemisphere. Although the antenna was designed to operate at a frequency of 1.6 GHz, it performed satisfactorily over the frequency range from 1.4 to 1.8 GHz. The antenna was fabricated and the computational results were verified experimentally. We have shown that the genetic algorithm is a very powerful tool for designing wire antennas; it is expected that this process can be used to design any antenna that can be analyzed using an electromagnetic code     

用于无线局域网的轴向模螺旋天线设计

根据无线局域网通信天线的要求,设计了三种工作在5GHz频段性能良好的轴向模螺旋天线,其中一种为普通螺旋天线,第二种为加绕寄生螺旋天线,第三种为锥形加绕寄生螺旋天线。通过电磁仿真软件HFSS计算及对结果分析表明,加绕寄生螺旋将改善天线的轴向辐射特性,而锥形结构将扩展天线带宽。     

Synthesis method for broad-band tapered wire antennas and itsexperimental verification

A method for synthesizing the geometry of extremely broadband tapered wire antennas used as part of a broadband spectrometer for millimeter and submillimeter waves is presented. The antenna is designed to have a nearly constant gain and a low voltage standing-wave ratio (VSWR) over a bandwidth of at least 20:1. After the synthesis, the characteristics of the antenna are analyzed by the moment method using a system of reaction integrals as described by Richmond (1974). An antenna version with resistively loaded ends of the wires has a mean gain of 5.7 dBi and a maximum gain variation of ±1.25 dB. The VSWR is equal to 1.7 over almost the entire frequency range peaking only to 2.6 at the lowest frequency. These theoretical results were verified by measurements in the frequency range from 1 to 18 GHz with a scaled model of the tapered wire antenna     

用于整流天线的口径耦合圆极化微带天线的设计与实验

提出了一种用于整流天线的新型圆极化微带天线形式，此天线采用单端口径耦合馈电，易与整流电路集成和匹配。利用电磁场仿真软件分析了天线参数对天线性能的影响，设计并加工了一个圆极化天线单元。设计值和实验值较吻合，实验结果表明该天线在10．25GHz具有良好的圆极化特性：在最大方向上圆极化轴比为0．3dB，3dB圆极化带宽达到160MHz，驻波比小于2的带宽达到800MHz。     

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.     

Design and analysis of single and multi-input multioutput triple-band metamaterial inspired antennas for WiMAX,WLAN, and satellite applications

This work proposes an electrical compact triple-bands antenna founded on a composite left-/right-handed approach. This structure contains a rectangular patch combined with two unit cells based on the metamaterial properties that are used to produce wide electrical lengths in miniature physical sizes. Thus, the presented antenna is designed with a lower resonant frequency and miniature physical dimensions compared to conventional antennas. The suggested antenna has been produced on top of the FR4 substrate having tan δ = 0.022, εr = 4.58, and a size of 28 × 16 × 1.6 mm³. This structure provides three bandwidths of (2.391–2.54 GHz), (3.42–3.56 GHz), and (5.02–11.40 GHz). Additionally, a multi-input multioutput (MIMO) antenna is designed by placing two similar radiating patches in a perpendicular shape. Therefore, this design approach has been used to achieve an important isolation among ports and less than −30 dB at frequency bands. The results of radiation patterns, envelope correlation coefficient, diversity gain, and channel capacity loss are below to 0.06, 10 dB, and 0.4 b/s/Hz respectively, which confirms that the MIMO antenna is compatible with wireless MIMO devices. These antennas have been modeled and experimentally confirmed, and the results have proven that the suggested antennas are useable and can support multi-standard wireless applications.     

On the performance properties of the Koch fractal and other bent wire monopoles

Koch fractal monopole antennas are known to exhibit lower resonant frequencies than Euclidean monopoles of the same height. It has been concluded that there exists a unique relationship between the antenna's fractal geometry and its electromagnetic behavior. Here, the performance properties of the Koch fractal monopole are examined and compared with the performance properties of other bent wire geometry monopoles having the same total wire length and overall height. It is demonstrated that monopoles with less complex shapes exhibit lower resonant frequencies because they are more effective at increasing the electrical volume of the antenna. When these antennas are made to be resonant at the same frequency, they exhibit virtually identical performance properties independent of differences in their geometric shape and total wire length. It is also demonstrated that the effective height of these monopoles converge to that of an electrically small Euclidean monopole near the small antenna limit and they exhibit virtually identical radiation resistance properties at low frequencies. Finally, it is shown that the fractal limit in lowering of resonant frequency is related to the limit in the increase in the antenna's effective volume.     

Modeling of normal-mode helical antennas at 900 MHz and 1.8 GHz formobile communications handsets using the FDTD technique

A simple technique is proposed for modeling short normal-mode helical antennas using a commercial finite-difference time-domain (FDTD) code with a rectangular grid and a nominal extension of the wire. The approach allows affects on the input impedance and radiation performance of the helix to be examined and importantly does not require modification of the excitation subroutines. Normal-mode helical antennas for mobile communications use at 900 and 1800 MHz were designed using the proposed method and good agreement with measurements of impedance and near-magnetic field strength was found. The radiating performance of the helix was compared to that of a λ/4 monopole and generally found to be inferior at 900 MHz due to only 19.2 % efficiency in the presence of the head. At 1.8 GHz the two antenna types showed similar characteristics except in regard to bandwidth, 36.1 % for the monopole and 7.8 % for the helix, in the presence of the head. The modeled helix antennas produce spatial peak specific absorption rate (SAR) figures that are up to 27 % greater at 900 MHz and up to 49 % greater at 1.8 GHz than the corresponding monopole values due to the shorter antenna     

Equivalent circuit model-based design and analysis of microstrip line fed electrically small patch antenna for sub-6 GHz 5G applications

In this paper, an equivalent circuit model-based electrically small patch antenna is designed for sub-6 GHz 5G application (3.5 GHz) using 50-Ω microstrip line feed. The overall size of the proposed antenna is 0.33λ₀ × 0.4λ₀ × 0.019λ₀ (28 × 34 × 1.6 mm³) at 3.50 GHz frequency. The proposed antenna has a tilted Y-shape slot, two rectangular shape slots, and two rectangular shape notches in the radiating patch. The proposed antenna is resonating from 3.21 to 3.74 GHz covering the entire sub-6 GHz 5G band (3.3–3.8 GHz). The impedance bandwidth (simulated) of the proposed antenna has been obtained 530 MHz resonating at 3.50 GHz frequency. The good return loss of −23.62 dB is also obtained at 3.50 GHz resonant frequency. The simulation results and geometry of the proposed antenna are validated with equivalent circuit model and experimental measurement of prototype antenna using vector network analyzer (VNA) and anechoic chamber. In the whole operating frequency range, the measured findings show reasonable agreement with the simulated ones. The measured impedance bandwidth of the proposed antenna has been obtained 480 MHz (3.21–3.69 GHz) resonating at 3.48 GHz frequency with a return loss of −21.61 dB, while the theoretical impedance bandwidth of the proposed antenna has been obtained 720 MHz (3.18–3.90 GHz) resonating at 3.58 GHz frequency with a return loss of −21.5 dB. The peak gain of 3.39 (simulated) and 3.2 dB (measured) is obtained at 3.50 GHz frequency. Moreover, the antenna shows 97% (simulated) and 95% (measured) efficiency at 3.50 GHz frequency.     

Hepta-Band Internal Antenna for Personal Communication Handsets

Modern personal communication handsets are shrinking in size and are required to operate at multiple frequency bands for enhanced functionality and performance. This poses an important challenge for antenna designers to build multiband antennas within the limited allowable space. In this paper, an internal antenna covering seven frequency bands is presented for personal communication handsets. The proposed antenna operates at GSM (880-960 MHz), DCS (1710-1880 MHz), PCS (1880-1990 MHz), UMTS (1900-2170 MHz), WiBro (2300-2390 MHz), Bluetooth (2.4-2.48 GHz), and WLAN (5.0-5.5 GHz) frequency bands. Measured input return loss of the antenna is better than dB at all the frequency bands with reasonable radiation performance. Antenna volume is 30 mm times15 mm times 4.0 mm (1.8 cm) that makes it attractive for modern multiband and multifunctional slim handsets.     

A survey of possible passive antenna applications ofhigh-temperature superconductors

A survey of possible applications of high-temperature superconductors (HTSs) to antennas and antenna feed networks is presented. The frequency range considered is 1 MHz for 100 GHz. Three antenna application areas seem appropriate for HTS material: electrically small antennas and their matching networks; feed and matching networks for compact arrays with enhanced directive gain (superdirective arrays); and feed networks for millimeter-wave arrays. Preliminary experimental results are presented on YBaCuO and TlBaCaCuO 500 MHz half-loop antennas that show an increase in radiation efficiency (compared with a copper antenna at the same temperature) by a factor of 5 for the HTS antennas     

应用于WLAN/WiMAX的三频单极子天线设计

设计了一种三频段L型单极子平面天线,通过3个L型单极子天线的组合,使其中一个单极子天线工作于3.5 GHz频段,较长一个单极子工作于2.4 GHz频段,较短一个单极子工作于5.8 GHz频段,该天线与其他三频段平面天线相比,结构更为简单。为数值分析和优化,在HFSS建立了该天线的电磁仿真模型,仿真结果表明,该三频段天线在其3个工作频段内的回波损耗都＜-10 dB,实现了2.4 GHz,3.5 GHz和5.8 GHz 三频段同时工作。该天线可在WLAN和WiMAX通信系统中得到良好的应用。     

Numerical analysis of bodyworn UHF antenna systems

Bodyworn antennas are found in a wide range of medical, military and personal communication applications, yet reliable communication from the surface of the human body still presents a range of engineering challenges. At UHF and microwave frequencies, bodyworn antennas can suffer from reduced efficiency due to electromagnetic absorption in tissue, radiation pattern fragmentation and variations in feed-point impedance. The significance and nature of these effects are system specific and depend on the operating frequency, propagation environment and physical constraints on the antenna itself. This paper describes how numerical electromagnetic modelling techniques such as FDTD (finite-difference time-domain) can be used in the design of bodyworn antennas. Examples are presented for 418 MHz, 916·5 MHz and 2·45 GHz, in the context of both biomedical signalling and wireless personal-area networking applications such as the Bluetooth^TM wireless technology     

A triband swastika shaped patch antenna with reduced mutual coupling for wireless mimo systems

A novel compact Swastika shaped patch antenna is designed in the present work, which can be used for Multiple Input Multiple Output (MIMO) systems. The proposed two element MIMO system resonates at a triband of 3.3 GHz, 5.8 GHz, and 7.1 GHz with an improved impedance bandwidth of 37% and a reduced mutual coupling of ?33 dB. These results are better compared to a normal E shaped patch antenna designed with same size and thickness, achieved without using any additional decoupling methods. A 2??2 MIMO system employing the Swastika shaped patch antennas is analyzed using computational electromagnetic ray tracing software for an indoor environment. The results show an improvement in the capacity compared to a 2??2 MIMO system developed with dipole antennas. The proposed antenna is a good choice for MIMO systems operating for several Ultra WideBand (UWB) applications.     

基于UHF频段及微波段分型天线研究

针对工作在UHF频段和微波频段的RFID系统(射频识别系统)要求,设计满足915MHz和2.45GHz多频特性的分型天线,提出采用方形Sierpinski毯结构。针对目前分型天线谐振频率所成的1∶3∶9的特性分析,并对天线部分参数改变,并对二阶毯型贴片天线进行开槽分析研究,提高天线性能,对高频部分降频以达到系统所要求915MHz和2.45GHz的中心频率,达到谐振频率的同时并保证理想的10dB回损带宽。     

Electrically small self-resonant wire antennas optimized using agenetic algorithm

One of the major limitations of electrically small antennas is that as the size of the antenna is decreased its radiation resistance approaches zero and its reactance approaches plus or minus infinity. Most small antennas are inefficient, nonresonant and, thus, require matching networks. In this investigation, we use a genetic algorithm (GA) in conjunction with the numerical electromagnetics code to search for resonant wire shapes that best utilize the volume within which the antenna is confined. Antenna configurations, over a ground plane, having from two to ten wire segments, were optimized near 400 MHz and then built and tested. As the cube size deceased from a side length of 0.096λ to 0.026λ, the computed Qs increased from 15.8 to 590. The measured Qs increased from 16.0 to 134 for cubes of 0.093 to 0.037λ on edge. This process for designing small antennas using a GA produced new self-resonant antenna configurations     

The Radiation Properties of a Novel Wire Antenna for the Security Fence Radar

The radiation properties of a novel wire antenna are investigated. The main part of this antenna is a sinusoidal wire undulator, which radiates by coupling electromagnetic energy from a Goubau line located near the antenna. Far-field patterns and S-parameters composed of three sets of antenna are measured. The measured patterns are compared with the calculated ones and the phase and attenuation constants of all the antennas are calculated. Frequency behavior and the dependency on the antenna dimensions of those wave parameters are investigated. Measured and calculated field patterns are also compared with the MoM patterns and some properties of the wave propagating along structure are explained by using MoM current distributions. It is shown that a broadside transversal radiation occurs in a narrow frequency band. The radiation intensity strongly depends on the coupling distance between the Goubau line and the sinusoidal undulator. This antenna is used as the basic element of the security fence radar antenna array working at 1.25 GHz in the L-band, which detects intruders approaching the fence. The performance of the antenna in the array is investigated and the near field distribution of the array is measured. The received signals caused by an intruder are given. The effects of rain and wind are also considered. The results suggests that the security fence radar introduced in this study can be used for the perimeter control of closed areas such as airports, malls, etc.      

一种双频左/右旋圆极化可重构环形缝隙微带天线

设计了一种频率比为1.9的双频左/右旋圆极化可重构环形缝隙微带天线,其在高频段和低频段分别工作于线极化和圆极化状态。在该天线中,环形缝隙和相互正交的四个缝隙臂将接地面分为五部分,缝隙臂上跨接两对PIN二极管开关和隔直电容。通过二极管开关的控制,天线在低频频率上可实现左/右旋圆极化的切换,在高频频率上则可保持其线极化性能不变。实验结果表明,天线在1.6 GHz的低频段上具有12.5%的3 dB轴比带宽,在3.06 GHz的高频段上其–10 dB阻抗绝对带宽为100 MHz,成线极化状态,辐射方向图近似不变。     

Wideband Planar Folded Dipole Antenna With Self-balanced Impedance Property

A planar folded dipole antenna that exhibits wideband characteristics is proposed. The antenna has simple planar construction without a ground plane and is easy to be assembled. Parameter values are adjusted in order to obtain wideband properties and compactness by using an electromagnetic simulator based on the method of moments. An experimental result centered at 1.7 GHz for 50 impedance matching shows that the antenna has bandwidth over 55% . The gains of the antenna are almost constant (2 dBi) in this frequency band and the radiation patterns are very similar to those of a normal dipole antenna. It is also shown that the antenna has a self-balanced impedance property in this frequency band.     

多根细线天线对超宽带信号的瞬态响应特性

利用FDTD(时域有限差分)方法对多根未加载的细线天线以及加载的细线天线瞬态响应特性进行了数值模拟。分析了其他细线天线的存在对馈源为电磁脉冲的细线天线辐射特性的影响以及入射波为电磁脉冲时细线天线中心的电流响应特性的影响。指出了在确定天线是否相关时,天线之间的距离所应当满足的条件。