用于金属表面的UHF RFID标签天线优化设计

UHF RFID 标签天线置于金属表面会引起阻抗变化以及阻抗失配,因此为了减小金属表面的影响,提出一种用于金属表面的UHF RFID 标签天线阻抗匹配优化设计方法。首先在折叠偶极子天线臂上附加短路段来调整标签天线的输入阻抗,通过粗略调节短路段的位置使天线和RFID 标签芯片在金属表面达到阻抗的基本匹配,然后利用遗传算法优化得到天线最优的长度、宽度和短路段位置,使天线和RFID 标签芯片在金属表面达到准确的阻抗匹配。所设计天线阻抗及方向图的仿真和测试结果表明该优化设计方法能够使RFID 标签天线在金属表面正常工作。     

一种基于FDTD的简单有效的天线阻抗计算方法

本文从有源区的软激励时Yee差分方程出发,推导了一种适用于理想的间隙激励(δ-gap source)和探针激励的天线输入阻抗新的计算公式,该方法简洁、有效,公式物理意义明确,能够有效地消除硬激励(hard source).计算天线阻抗时,在频率很低接近零时阻抗值的严重失真,使得应用时域有限差分法计算天线输入阻抗变得更加快捷适用.最后,本文应用该方法分别计算了一个单极子天线和同轴馈电的微带天线,单极子天线的计算结果和前人的计算结果吻合得很好,并且消除了频率接近零时以前计算结果的严重失真,微带天线和已有软件的计算结果进行了比较,得到了满意的结果.     

基于多项式的弯折偶极子射频识别标签天线阻抗预测研究

在解决射频识别(RFID)标签天线设计中阻抗计算速度慢的问题的过程中,针对其中较为复杂的阻抗耦合情况,该文提出一种基于多项式的弯折偶极子RFID标签天线阻抗预测方法.首先使用基于天线尺寸的阻抗变换与线性化假设建立模型假设;然后在具体的天线结构中收集数据并进行相关性分析与回归拟合验证假设正确性;最后实验验证使用该方法进行...     

基于多项式的弯折偶极子射频识别标签天线阻抗预测研究

在解决射频识别(RFID)标签天线设计中阻抗计算速度慢的问题的过程中,针对其中较为复杂的阻抗耦合情况,该文提出一种基于多项式的弯折偶极子RFID标签天线阻抗预测方法.首先使用基于天线尺寸的阻抗变换与线性化假设建立模型假设;然后在具体的天线结构中收集数据并进行相关性分析与回归拟合验证假设正确性;最后实验验证使用该方法进行的阻抗预测相对于计算机仿真的准确性、高效性与普适性.试验结果表明,使用该方法替代计算机进行弯折偶极子RFID标签天线阻抗计算时,其预测阻抗相对于计算机仿真结果在保持较高预测准确率的同时极大地缩短了阻抗计算时间,同时该方法在中国应用频段上针对不同弯折次数的弯折偶极子RFID标签天线仍然适用.     

The signal produced in a monopole antenna by the gamma flux from a nuclear explosion

A monopole antenna is considered to be bombarded by a flux of gamma rays propagating normally to the axis of the antenna. As a result of this bombardment, electrons are scattered from the antenna, thus charging the antenna positively. This induces a current in the load impedance of the antenna-appearing as if the antenna were receiving a transient RF signal. An expression for the time dependent voltage across the load impedance of the antenna is obtained by considering that every electron scattered from the antenna never returns and that the antenna impedance and capacitance are their free-space values.     

扫频仪测圆环天线输入阻抗值的可行性研究

用扫频仪测量天线的输入阻抗时，在同轴传输线与天线间应按平衡—不平衡变换器。针对圆环天线的输入阻抗为复阻抗，提出了一种新的四分之一波长平衡一不平衡变换器，得到了实验结果，并进行了讨论。     

折叠偶极子天线的设计

射频识别(RFID)应用中的天线设计需考虑的最重要因素是低价位、小剖面和小型化,而为了最大功率传输,天线的输出阻抗必须和其后的芯片的输入阻抗匹配。本文介绍一种新颖的简单结构折叠偶极子天线,所需的输入阻抗能通过选择合适的几何参数轻易获得,这对设计特殊阻抗的天线非常有用。     

基于阻尼振荡法的甚低频天线阻抗测量

为了准确测量甚低频发射天线在实际工作环境和工作频点上的输入阻抗,本文提出了一种基于RLC阻尼振荡法的阻抗测量方法,并推导了天线阻抗、电容、电感和电阻的测量公式;该测量方法可通过提高测量电压来提高测量信噪比和测量精度;测量系统谐振于被测天线的工作频点或其附近,使甚低频发射天线输入阻抗的测量值更接近天线在实际工况下的真实值.试验表明,本文提出的测量方法简单可行,具有较高的精度和稳定性,可实现甚低频发射天线输入阻抗的现场测量.     

The terminal voltage of a receiving dipole antenna

The terminal voltage of a receiving dipole antenna is dependent on the antenna current distribution which in turn is dependent on its feed-point load impedance. Computed results of the terminal voltage are presented for dipole antenna half-lengths up to1.0 lambda. Representative values of the antenna load impedance, resistive, inductive and capacitive, are used to show their effects on the terminal voltage.     

Planar inverted-F antenna for radio frequency identification

A small and low-cost antenna solution for radio frequency identification (RFID) tags is presented. The impedance of the antenna is designed to match directly to the impedance of the RFID microchip. Also, the impedance of the antenna is immune to the platform. Thus, the antenna is applicable in many different environments. The design and measurement results are reported and discussed.     

Impedance and large signal excitation of satellite-borne antennas in the ionosphere

The input impedance of a spacecraft-borne electric antenna operating below approximately 30 kHz in the ionosphere is investigated with emphasis on sheath effects. The impedance concept is generalized to be applicable to nonlinear antenna-magnetoplasma systems. Explicit formulas are obtained for the generalized impedance of a near cylindrical antenna taking into account the effects of large signal excitation, induced electromotive forces due to antenna motion across the Earth's magnetic field, the influence of the ion collection surface of the space vehicle, and of dc bias between antenna and vehicle. Comparison is made of the pertinent part of the theory and LOFTI-IIA satellite data.     

The traveling-wave linear antenna with nondissipative loading

An approximate theory for a doubly impedance loaded, traveling-wave linear antenna is presented. The distribution of current on the thin, cylindrical antenna is determined approximately in terms of its dimensions and the impedance and position of the lumped impedance loading. From this result, the optimum loading required to excite an outward traveling current wave along most of the cylinder is determined. Significantly, it is indicated that a purely reactive loading may be utilized if its location is properly chosen. Expressions for the input impedance and radiation fields of the traveling-wave antenna are presented. An experimental study is made of a traveling-wave cylindrical antenna utilizing a purely nondissipative loading. Numerical results from the theory are compared with experimental data, and an excellent agreement is noted. The technique described may be utilized to realize a high-efficiency traveling-wave antenna.     

Novel design of broad-band stacked patch antenna

A novel broadband stacked E-shaped patch antenna is proposed in this paper. The proposed antenna has an input impedance bandwidth of about 38.41%, better than the conventional E-shaped microstrip patch antenna, which has an input impedance bandwidth of 33.8%. Through the use of the washer on the probe of the stacked patch antenna, the input impedance bandwidth is improved further to 44.9%. The radiation patterns are found to be relatively constant throughout the whole band. Comparisons of these antennas are presented in this paper.     

New exponential TEM horn antenna with binomial impedance taper

In this paper a new ultra wide band exponential transverse electro-magnetic (TEM) horn antenna with binomial impedance taper is presented. The binomial distribution is used for the impedance taper along the length of the proposed antenna. Using binomial distribution for the impedance taper causes the antenna to have minimum VSWR and flat gain in a wide frequency band. The proposed antenna was manufactured and its performance was compared with the antennas of the same size with exponential, Klopfenstein and triangular impedance tapers. Measurements show that the antenna has VSWR less than 2 in the frequency band from 3 to 15 GHz and less than 2.5 from 2 to 16.3 GHz. Having very good directional pattern and flat gain in a wide frequency band are significant characteristics of this new proposed antenna.     

柱形等离子体天线阻抗及辐射特性实验研究

借助天线测试系统,实验研究了柱形等离子体天线的阻抗特性和辐射特性。实验结果发现:该柱形等离子体天线与相同构造和尺寸的金属天线相比,具有较好的宽带阻抗特性;柱形等离子体天线的相对增益在50～260MHz频带范围内与金属天线相差不大;等离子体发射天线相对增益略高于等离子体接收天线。     

射频识别系统微带二元天线阵的设计

本文介绍了目前常用的一些射频识别系统天线,并简要分析矩形微带天线的工作原理,在此基础上,设计出一种工作在2.45GHz的微带二元天线阵,同时在同相侧馈的馈电网络中进行天线的阻抗匹配。最后测得天线的驻波比、输入阻抗、增益和方向图。结果表明,二元阵天线的增益明显优于普通贴片天线,适合作为射频识别系统天线使用。     

对平面螺旋天线阻抗变化方式及其性能的优化

提出一种新的平面等角螺旋天线的阻抗变换方式,在此基础上设计并优化了一个工作于860MHz～960MHz的等角平面螺旋天线,使得天线在该频段上实现VSWR<1.4的性能。仿真显示在天线尺寸有限制的情况下,提出的新的馈电方式的天线设计实现了小型化的同时能取得较好的性能。     

Bounds of Uncertain Interference Between Closely Located Antennas

The uncertainty in the characteristics of two antennas located close together and operating at different frequencies is considered. The formulations of antenna performance indexes on one antenna by admittance parameters are obtained with respect to the load impedance at the feed point of the other antenna. All the antenna performance indexes obtained here are expressed as the ratio of quadratic functions of the load impedance, and exact formulas are derived for the quick calculation of their bounds with respect to the load impedance which is uncertain and changes with frequency.     

反射面相控馈源阵的动态阻抗匹配

对于相控阵馈源,其前端低噪放的噪声系数直接影响系统整体性能,在技术途径上,减小系统前端噪声系数的关键之一就是改善阵元与有源前端的匹配,即阻抗匹配。对于单个天线,阻抗匹配就是使得天线的输入阻抗等于低噪放的最佳源阻抗。但是对于相控阵,阵列的动态阻抗依赖于波束形成系数并且随着波束指向的变化而变化,阻抗匹配是比较复杂的。针对反射面相控馈源阵系统,采用HFSS鄄MATLAB 联合仿真的方法,设计了馈源天线和低噪放,自动完成天线参数和低噪放最佳源阻抗的优化实现动态阻抗匹配和多波束平均最优阻抗匹配,最后系统仿真进行了验证。     

带有开口谐振环引向器的新型端射天线设计

设计一种带有开口谐振环(SRRs)引向器的新型端射天线。天线由反射板、地板、辐射单极子和开口谐振环组成。天线的反射板结构使天线在低频处阻抗匹配,有效地提高了天线带宽;用六对开口谐振环结构作为天线的引向器,很好地实现了天线的高增益。仿真和实测结果表明,天线阻抗带宽达到73.7%(2～4.21 GHz),增益为4.3～10.3 dB;在天线的带宽内,天线的辐射方向图稳定,设计的天线满足S波段无线通信领域的需求。