对数周期曲线振子天线的分析与设计

对数周期天线小型化的一种途径是利用新的谐振天线(如V型天线、螺旋天线、分形天线等)代替半波振子来降低谐振高度,这些对数周期天线可以统称为对数周期曲线振子天线.利用基于Nakano方程的矩量法结合等效电路理论来分析对数周期曲线振子天线的新方法,并对几种小型化的对数周期天线进行了研究.计算机仿真表明:该算法简单易行,为研究新型结构的对数周期天线和对数周期天线的小型化提供了一种新途径.     

A Circuit-Theoretic Approach to the Design of Quadruple-Mode Broadband Microstrip Patch Antennas

A novel method for the design of broadband patch antennas is described. The approach taken is to broadside couple two dual-mode patch antennas, resulting in a quad resonance antenna. The equivalent circuit of the antenna is similar to that of microwave filters, thus filter design techniques maybe employed to synthesize the antenna to obtain maximum return-loss bandwidth. This is the first time an increase in the bandwidth is achieved on a relatively thin substrate antenna as a result of coupling four resonant modes using two stacked circular microstrip patches. Electromagnetic simulation and measured results demonstrate bandwidth improvement of over four times that of a single-mode design.     

The Use of the Lorentz Reciprocity Theorem to Prove Equality of the Open-Circuit Voltages of a Receiving Dipole and a Monopole

A common error is made by antenna engineers in the calculation of the load current in monopole (and slot) receiving antennas. The mistake is to assume that the open circuit voltage at the terminals of the monopole is precisely one-half the open-circuit voltage of the equivalent dipole. It is shown in this paper by physical reasoning, as well as analytical argument, that the open-circuit voltages of both structures are identical. It is particularly important in dealing with receiving antennas over a ground plane not to neglect the image source that effectively doubles the field acting on the receiving configuration.     

矩量法结合网络理论分析对数周期偶极天线

本文利用路－阵方法分析了对数 周期偶极天线。采用矩量法分析天线阵网络,网络理论分析集合线网络。借助集合线网络、天线阵网络和矩量法分段上电压电流的联系,把两个网络有机结合,给出形式简洁的天线电流分布解,并减少了计算量。     

Design Considerations on the Minimum Size of Broadband Antennas for UWB Applications

The practical realization of Chu's minimum-sized antenna is investigated using self-complementary antennas. Rigorous bandwidth formulas for broadband antennas are derived for broadband antennas based on Chu's fundamental mode equivalent circuit. By comparing input impedances and radiation patterns, the fabricated self-complementary antenna used for Japan's ultra-wideband higher band (7.25-10.25 GHz) is found approximated by the minimum-sized antenna. Using the rigorous bandwidth formulas above, the fabricated antenna is shown to be smaller than the minimum-sized antenna. This breakthrough is achieved by using a more complicated matching circuit for broadband antennas instead of the single-stage inductor used in bandwidth estimation with the Q factor.     

Transmitting, receiving, and scattering properties of antennas

In most modern textbooks on antennas, it is stated that receiving antennas scatter as much as they absorb under matched-load conditions. This is incorrect, as was shown 50 years ago. The reason for this discrepancy is an apparently incorrect use of the equivalent circuits. In this tutorial paper, a simple example of a two-element Yagi antenna and a test dipole in the far field is analyzed for transmission, reception, and scattering, through the use of the symmetric impedance matrix. It is shown that the correct equivalent circuit for the scattering case is more complicated, owing to the existence of more sources than in the transmitting case. Through a numerical example, it is also shown that the scattered power may be larger, equal to, or smaller than the absorbed power.     

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。     

X 波段加膜片式单脊波导裂缝天线的研究

等效导纳值是波导宽边纵缝天线的关键设计参数。为克服传统波导裂缝天线副瓣偏高、设计效率低下等问题,本文提出了一种单脊波导裂缝天线的改进设计方法,在传统波导裂缝阵列天线设计的基础上,利用等效导纳值对天线等效电路的影响,在裂缝单元下增加金属膜片,通过改变金属膜片的高度,优化裂缝等效导纳值,使得每个裂缝口径场分布更加接近于理论设计值,并在设计过程中使用牛顿迭代法提取导纳进一步缩短设计时间。通过设计实例表明:应用此方法设计单脊波导裂缝天线能够有效抑制副瓣电平,天线方位面副瓣电平可达到-30 dB 以下;在满足主要指标要求的前提下,设计效率显著提升。     

5G传播损耗及链路预算

针对5G发展对室内接入天线提出的新要求,设计了一种可在N78（3.4~3.6 GHz）与N79（4.8~5.0 GHz）两个频段之间切换的频率可重构天线. 天线辐射器印制在电路板上,电路板末端带有圆形金属腔,作为八木天线与短背射天线的反射器. 对PIN二极管偏置电路进行优化,切换天线有源振子臂上一对PIN二极管开关,使天线具有两种工作模式,具备频率可重构的功能. 通过仿真软件对天线模型进行仿真分析,根据仿真结果制作了天线的实物并进行实验验证,实测表明天线具有良好的匹配与增益. 当PIN二极管导通时,天线工作在N78频段,回波损耗小于−19.58 dB,增益大于7.44 dBi;当PIN二极管断开时,天线工作在N79频段,回波损耗小于−18.58 dB,增益大于9.48 dBi.

     

基于新型复合左右手传输线的零阶谐振天线

通过在共面波导上引入周期排列的缝隙和二阶Hilbert分形接地曲线,实现了一种新型复合左右手传输线。在等效电路模型的基础上,利用HFSS和Serenade软件对该传输线的电路参数进行了拟合。拟合出的电路参数表明:该传输线可以用于设计具有较宽带宽的小型化零阶谐振天线。作为验证,设计并制作了一个两单元零阶谐振天线。实验结果表明:该天线比之前报道的复合左右手零阶谐振天线具有更小的电尺寸和更宽的工作带宽。基于这些优点,该天线可以用于现代通信系统中。     

Compact and contact quad-band (DVB-H UHF/L, WLAN 11a/b) antenna for PMP applications

The quad-band antenna, which is composed of two compact dual-band antennas, is presented for potable media player (PMP) applications. The antenna for the broadcasting dual-band (DVB-H UHF; 470 - 862 - MHz, L; 1452 - 1492 - MHz) is composed of a planar inverted F-shaped antenna with an input matching circuit. The antenna for the communication dual-band (WLAN 11b; 2.4 - 2.5 - GHz, 11a; 5.15 - 5.8 - GHz) is composed of a folded dipole antenna with enhanced mutual coupling. The proposed antennas are contact with the PMP case (?_r = 3.2) which is used as a substrate for size reduction and compact design.     

Electrostatic resonance-cone waves emitted by a dipole in theionosphere

The theory of whistler-mode radiation from a dipole antenna has been tested in the ionospheric sounding-rocket experiment OEDIPUS-C (OC). In this bistatic investigation, 25-kHz waves were received at a distance of 1200 m from a synchronized transmitter. Electric fields near the group resonance cone were significantly stronger than in other directions, as predicted by theory. The transmitting antenna RF current was obtained from an equivalent circuit including an antenna impedance predicted by quasistatic theory. This current was applied to resonance-cone radiation theory. Observed radiated levels are about a hundred times greater than theoretical predictions based on some assumptions about the electromagnetics of the transmitting and receiving antennas. The modulation of the received signal caused by the spins of the transmitting and receiving dipoles was consistent with the electric field being polarized predominantly along the electrostatic wave-vector direction     

The polarization losses of offset paraboloid antennas

In this paper the electric field in the aperture of offset front-fed paraboloid antennas and open Cassegrainian antennas, excited by an electric dipole or Huygens source in the focus, is compared with the fields of front-fed circularly symmetrical paraboloid reflector antennas and classical Cassegrainian antennas. The aperture field forms the basis of expressions to calculate the polarization efficiency of all four types of antenna. Computed results are given, showing that offset antennas can compete with front-fed paraboloids if they are excited by an electric dipole; the classical Cassegrainian antenna, however, shows better results. If offset antennas are excited by a Huygens source, the result is very unfavorable compared with the symmetrical antennas which show no cross polarization.     

Reversibly Deformable and Mechanically Tunable Fluidic Antennas

This paper describes the fabrication and characterization of fluidic dipole antennas that are reconfigurable, reversibly deformable, and mechanically tunable. The antennas consist of a fluid metal alloy injected into microfluidic channels comprising a silicone elastomer. By employing soft lithographic, rapid prototyping methods, the fluidic antennas are easier to fabricate than conventional copper antennas. The fluidic dipole radiates with ≈90% efficiency over a broad frequency range (1910–1990 MHz), which is equivalent to the expected efficiency for a similar dipole with solid metallic elements such as copper. The metal, eutectic gallium indium (EGaIn), is a low‐viscosity liquid at room temperature and possesses a thin oxide skin that provides mechanical stability to the fluid within the elastomeric channels. Because the conductive element of the antenna is a fluid, the mechanical properties and shape of the antenna are defined by the elastomeric channels, which are composed of polydimethylsiloxane (PDMS). The antennas can withstand mechanical deformation (stretching, bending, rolling, and twisting) and return to their original state after removal of an applied stress. The ability of the fluid metal to flow during deformation of the PDMS ensures electrical continuity. The shape and thus, the function of the antenna, is reconfigurable. The resonant frequency can be tuned mechanically by elongating the antenna via stretching without any hysteresis during strain relaxation, and the measured resonant frequency as a function of strain shows excellent agreement (±0.1–0.3% error) with that predicted by theoretical finite element modeling. The antennas are therefore sensors of strain. The fluid metal also facilitates self‐healing in response to sharp cuts through the antenna.     

A Comparison of Two and Three Dimensional Dipole Antennas for an Implantable Retinal Prosthesis

The feasibility is investigated using three dimensional folded dipole antennas as a data-telemetry implantable receiving antenna in a dual-unit retinal prosthesis to restore partial vision to the blind. Three dimensional designs are explored in an effort to enhance certain antenna characteristics such as bandwidth and maximum gain while reducing the planar footprint size in comparison to its two dimensional equivalent. The current vector alignment between the three dimensional layers are examined through folding and rotating the dipole arms with respect to each other to fully optimize the antenna's characteristics. The performance of the 2D and 3D antennas were compared in simulations and further examined by fabricating and characterizing the performance in a transmit/ receive system in air and inside eye phantoms. Results show that three-dimensional antennas can provide larger bandwidth while being physically smaller than the correspondent two-dimensional ones, thus providing larger channel capacity that could lead to a system with an increased number of stimulating electrodes.     

一种基于开口谐振环的高增益宽带双极化天线设计

该文设计并制作了一种基于超材料的高增益宽带双极化天线,该天线由两个正交放置的印刷振子单元、馈电巴伦及金属接地板构成。为了进一步展宽带宽、提高增益,在天线上了加载开口谐振环、互补开口谐振环等超材料结构。测试结果表明,该天线回波损耗小于-10 dB的带宽约为69%(0.98~2.01 GHz),在相同的频带内隔离度大于20 dB。由于开口谐振环的引向作用,天线的辐射特性得到改善,增益最大提高了4.1 dB左右。和已有设计相比,该天线的总体高度减小了约12%。其可以当作独立天线使用,也可用作反射面天线的双极化馈源。     

An Equivalent Circuit Model for Broadband Modified Rectangular Microstrip-Fed Monopole Antenna

A new, simple equivalent circuit model for designing a multi-mode/broadband modified rectangular microstrip-fed monopole antennas using stepped cut at four corners (SCFC) method has been presented in this paper. The SCFC method is a method in which the four corners at the edges of the patch are cut for the purpose of designing the microstrip-fed monopole antenna. The design procedure of a single mode to a broadband microstrip-fed monopole antenna is explained in order to help understand more about the proposed equivalent circuit model and SCFC method. The computer simulation technology (CST) microwave studio and advanced design system (ADS) software are used to design and simulate of the proposed microstrip-fed monopole antennas and their equivalent circuit model, respectively. The operating bandwidth of the broadband antenna with \(\hbox {S}_{11}< -10\) dB, covers the operating frequency range from 0.9 to 2.6 GHZ that it is suitable for GSM (0.9 GHz), WiFi (2.4 GHz) and LTE (2.6 GHz) applications. For the purpose of validating the simulated results, the antennas prototype has been fabricated and measured. The comparison of the measurement and simulation results shows that, there is a good agreement between them.     

Backfire antennas with dipole elements

A method is set up for a theoretical investigation of arbitrary backfire antennas based upon dipole structures. The mutual impedance between the dipole elements of the antenna is taken into account, and the field radiated due to a surface wave reflector of finite extent is determined by calculating the surface current distribution on the reflector plate. Numerical results obtained for Yagi backfire antennas and short-backfire antennas using this theory are compared with experimental results.     

Formulation of normalized site attenuation in terms of antennaimpedances [EMI measurement applications]

General formulas for normalized site attenuation (NSA) are derived in terms of antenna impedances by using the two-port circuit theory to show the effects of mutual coupling. The investigations focus on the antenna factors and antenna calibration procedures that are appropriate for NSA, and the validity of the NSA concept is discussed on the basis of these theoretical investigations. The NSA measurements are found to be appropriate for site validation when using broadband antennas having constant antenna factors. It is theoretically concluded, however, that the original concept of the NSA may not be applicable to the use of tuned dipole antennas, even after adopting the correction factors specified in the existing ANSI standard. NSA is shown to require different correction factors if the antennas have changeable antenna factors