A new log-periodic dipole antenna

A log-periodic antenna having triangular dipoles as its constituent elements is presented. The design criterion and its electrical properties are discussed. The proposed configuration is compared with the conventional log-periodic dipole antenna. It is shown that this configuration offers a better frequency transition, bettor gain and a reduction in the axial length over the conventional log-periodic dipole array.     

水平对数周期天线空域极化

针对水平极化对数周期天线圆阵波束合成,分析了地面上短波对数周期天线空域极化特性.根据接收天线理论,推导了新的阵列流行,阐明了水平对数周期天线圆阵的内在极化机理.依据新的阵列流行,理论和实验分析了现有采用相位加权的波束合成方法的性能.指出了对于水平对数周期天线圆阵波束合成时,需要采用相位极化联合加权,仿真结果表明联合加权方法可以有效改善波束合成的效果.     

天线阵元相位中心的一种测量方法

分析天线阵元相位差与其相位中心的数学关系,建立了阵元相位中心的目标函数模型。基于实际的天线阵列测试系统对对数周期天线阵元相位中心进行测量,并利用最小二乘法求出阵元实际相位中心。分析比较了实测与理论的相位中心差异,结果表明:在大部分工作频率上实测结果与理论计算结果较一致,但在高频实测相位中心比理论相位中心更靠近馈电点;实际测量的相位中心能够有效地表征各阵元间实际相位关系。     

Use of log-periodic feeds in corner reflectors

A log-periodic dipole array is considered as a broadband corner reflector feed. Theoretical considerations predict a rather high VSWR and a pattern performance which is frequency independent over only a limited frequency range. Experimental results bear out the predictions and help indicate the possible usefulness of this type of antenna.     

CPW-fed log-periodic dumb-bell slot antenna array

A coplanar waveguide (CPW) fed log-periodic dumb-bell slot antenna array is presented. Due to the log-periodic structure and dumb-bell slot, the proposed antenna operates as a frequency independent antenna. The antenna is printed on a substrate with a single metal layer and therefore is easily constructed. The measured return loss and radiation patterns are also included.     

Continuously scaled transmission lines with applications to log-periodic antennas

The results of several studies on network models of log-periodic structures are described. A nonuniform, continuously scaled transmission line is introduced to simulate the near-field behavior of the log-periodic dipole array. The frequency-independent performance of the continuously scaled line represents the ideal, which is approximated by using lumped elements in a log-periodic structure. It is particularly significant to note that 1) the continuously scaled model predicts the observed input impedance behavior of log-periodic dipole arrays even when the frequency is approaching the high-frequency limit of the antenna, 2) phase velocity on the transmission line model in the active region and at the input region is also found to agree with experimental data, 3) increasing theQof the loading element increases the coupling to the reflected wave, resulting in increased variations of impedance. Decreasing the angle of taper of the antenna will compensate for the increase inQ. Based on this model, it is shown that true size reduction may be achieved only at the expense of efficiency.     

Microstrip Antenna–Oscillators Integrated with a Waveguide Built in a Dielectric Substrate

The design of a microwave oscillator based on a microstrip log-periodic antenna integrated with a field effect transistor and a waveguide built in a dielectric substrate has been developed and analyzed. The waveguide geometry provides the possibility of propagation and radiation at both the fundamental frequency of the log-periodic antenna and harmonics. Computer simulation of the oscillator design in a frequency range near resonance frequencies of the log-periodic antenna is conducted. The possibility of summation of powers of several antenna–oscillators arranged ias a linear phased array is investigated.     

双对数周期偶极天线扇形阵的研究

论述了双对数周期偶极天线扇形阵的设计方法,利用IE3D软件对单个对数周期偶极天线(LPDA)和双对数周期偶极天线扇形阵进行了优化仿真分析,并研制了天线实物样机,同时对该天线的电性能进行了测量.测量结果表明,该双对数周期偶极天线扇形阵具有宽带、高增益、小型化等特点,进而说明该设计方法是行之有效的.     

Multimode propagation on radiating traveling-wave structures with glide-symmetric excitation

Standing-wave measurements on a periodic traveling-wave array of dipoles driven with glide-symmetric excitation from a coaxial transmission line show the existence of multimode propagation in certain frequency bands. This phenomenon is explianed qualitatively in terms of coupling of symmetric and antisymmetric modes of the dipole array by the excitation from an unbalanced line. It has not been found when the dipoles are driven from a balanced two-conductor line. The avoidance of such multimode phenomena is crucial to the self-balancing property of successful log-periodic dipole arrays.     

超宽带多极化跟踪天线及馈源的设计

随着空间技术的快速发展,对目标飞行器的跟踪与信息截获变得越来越重要。为了实现对目标飞行器的跟踪和信息截获,文中设计了一种超宽带、多极化、高增益的跟踪天线及馈源,采用基于印制板设计的对数周期天线作为单元,并使用八个单元组成圆环阵作为反射面天线的馈源,对结构和馈电幅相进行设计,从而实现线极化比幅跟踪、左旋圆极化接收、右旋圆极化接收三种工作方式。仿真结果表明:单元天线驻波小于2的相对带宽达到147%,次级方向图的圆极化轴比小于4 dB,交叉波束的交叉电平基本稳定在-3 dB~-8 dB。对该跟踪天线进行加工,并进行天线系统测试,实际测试结果与仿真吻合很好。     

Bandwidth limitations of log-periodic microstrip patch antenna arrays

Results are presented for the frequency dependence of the propagation constant of uniform microstrip patch arrays that allow the bandwidth limitations of log-periodic patch arrays to be deduced. It is found that direct coupling of the patch to the feed line limits the log-periodic bandwidth to about a 2:1 frequency range. However, the introduction of series reactance into the equivalent circuit such as by the use of overlaid patches indicate that log-periodic action over a very wide bandwidth is possible which will then be limited by the uniform substrate and production tolerances.     

Helical log-periodic array

A helical log-periodic array is designed considering the same parameters as those used in an existing log-periodic dipole array. The impedance and radiation characteristics are measured for both arrays. It is observed that the arrays have similar characteristics. Moreover, the advantage of the helical array is that its transverse dimension becomes much smaller.     

Log-Periodic Transmission Line Circuits--Part I: One-Port Circuits

A theoretical study of one-port log-periodic circuits consisting of a transmission line shunt loaded with open-circuit transmisson lines is reported. The objective was to determine the conditions under which the phase of the input reflection coefficient varies linearly with the logarithm of the frequency. Precise definitions and general analytical techniques for log-periodic circuits are given. Results of extensive numerical calculations are presented to illustrate the dependence of the input reflection coefficient on the various design parameters. It was found that phase deviations from linear on the order of one degree are quite easily achieved.     

Near-field investigation of uniform periodic monopole arrays

Measurements of amplitude and phase of the fields close to a number of driven periodic arrays of monopoles have been made to determine frequency dependence of the propagation constant for such structures. The results have been analyzed, where possible, in terms of a single traveling wave along the structure, and dispersion curves are given which include attenuation as well as phase shift. These curves clearly illustrate the possibility of obtaining leading phase shift along the periodic structure that will produce backfire radiation. Experimental radiation patterns corroborate the near-field results. A simple theory is given for the backfire phasing in terms of the space-harmonic content of a Fourier series expansion for the fields of periodic structures. This theory predicts beam scanning for the periodic structures which is readily observed in the experimental models. The measured data are approximately applicable to tapered versions of the periodic structures which have log-periodic geometry. Examples of periodic structures that have frequency independent log-periodic counterparts as well as some that do not are discussed.     

对数周期偶极天线扇形阵的分析

采用矩量法对对数周期偶极天线扇形阵进行理论分析，在计算广义阻抗矩阵元素时，利用矩阵的互易性、天线阵的结构对称性和对数周期天线的工作原理进行了算法简化，从而在保证计算精度的前提下，大大提高了计算速度。     

Design of a stripline log-periodic dipole antenna

A procedure is given for designing a two-layer stripline log-periodic dipole (LPD) antenna array. Measured input impedance and far-field characteristics are demonstrated for a 12-element array for 1-2 GHz operation that are in good agreement with design specifications.     

短波水平极化测向中的交叉极化波

通过对水平偶极子和定向天线的计算,分析了水平天线对主极化波和交叉极化渡不同的幅相响应特性,并讨论了到达接收点的两个正交极化波之间的相关性和相干性,进而讨论了交叉极化波对水平极化测向精确度的影响.     

Mutual coupling between log-periodic antennas

Numerical techniques are used for the analysis of mutual coupling in arrays of log-periodic dipole antennas. The analysis is formulated in terms of impedance and admittance matrices for the dipole and transmission line networks. Approximations are made to allow the solution for moderately sized arrays to be practical with the existing generation of computers. Antenna patterns for the array are expressed in terms of the current incident on each log-periodic antenna. Results are presented for systems of one, two, and three log-periodic antennas.     

New wideband microstrip antenna using log-periodic technique

A novel wideband microstrip antenna using a series-fed linear array of patch resonators in a log-periodic arrangement is described. A 9-element example gives good input v.s.w.r. and radiation control over a 30% bandwidth with better than 70% efficiency. The new array configuration gives wider bandwidth than single-layer or stacked microstrip patches combined with better efficiency than patches on lossy substrates or microstrip spirals.