机载天线方向图回归研究

利用工程软件建立无人机及其天线的一体化仿真模型,综合考虑飞行姿态、机载天线对地面接收天线的极化匹配和方向性等因素,研究了机载天线对地面目标的干扰方向图.采用遗传算法,结合机载天线仿真的数值结果,设计适应度函数,进行方向图回归研究,得到了便于实际应用的解析公式.     

Multiple-frequency computer analysis of the log-periodic dipole antenna

Matrix methods for analysis of dipole antenna arrays have been applied to general computer programs but often require large amounts of computation time for multiple-frequency analysis of electrically long arrays, since most of the computations must be repeated for each frequency. It is shown how the special geometry of a leg-periodic dipole antenna may be exploited within the general framework of matrix methods to permit multiple-frequency analysis without the need to repeat all computations for each frequency. The computation of antenna currents at one frequency is made use of in solving for currents at a different frequency; the time consuming matrix inversion step is required only once.     

机载短波天线间隔离度的全波分析

对飞机等复杂形体及机载短波天线进行全波ＦＤＴＤ数值模拟所需的数学建模方法的介绍,研究了机载短波天线间隔离度的分析计算方法,并以波音７０７－３２０Ｂ飞机为例计算了机上４付短波天线间隔离度。所用方法及所得结果可作为飞机电磁兼容分析与设计的手段和依据。     

Unidirectional dipole antenna

A new small unidirectional wire antenna, useful for an indoor television receiving antenna, has been developed for use in the v.h.f. band. This antenna consists of two closely spaced dipoles. This letter describes the principle involved and introduces the equations for input impedance and gain. Experimental results show fairly close agreement with the theory.     

Compact size dipole antenna

A novel wideband planar dipole antenna is proposed. This antenna has a simple structure and compact size. For verification, the newly proposed structure was fabricated and measured. It is shown that the return loss of the antenna between 3.0 and 7.5 GHz is better than 2 10 dB. The radiation performance is good over the whole frequency band.     

Wiener-Hopf type analysis of dielectric-coated dipole antenna inrelatively dense medium

The problem of dielectric-coated dipole antennas in a relatively dense medium is solved using the Wiener-Hopf technique. The analysis is done for a perfectly conducting dipole antenna coated by a low-loss dielectric and embedded in a lossy medium of a wavenumber larger than that of the lossy coating. Analytic expression are derived for the input admittance and the current distribution along the dipole which is excited at the center across a nonzero width feed gap. Results are compared with available literature data for different antenna lengths embedded in an ambient medium with a loss tangent of σ/ω∈. The numerical work involves only the determination of certain integrals using standard integration routines     

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.     

Multi-band printed sleeve dipole antenna

A multi-band printed sleeve dipole is developed by using different strip pairs to compose various frequency resonances. The measured results of an example implemented for dual-band wireless LAN reveals its multi-band characteristic. The dipole-like radiation pattern and its compact dimension show that the design can satisfy the requirements of general communication.     

Low profile planar dipole antenna

The design and experimental results of a low profile planar dipole antenna with effective channel bandwidth are presented. The matching network of the design with a wider bandwidth tapered microstrip line to overlap the coplanar stripline transition that only provided unbalance to the balanced line created balanced equal power output and phase difference characteristics for the balanced feed dipole element.     

Analysis of a microstrip dipole antenna

Assuming a quasi-TEM mode of wave propagation and using a conformal transformation technique, accurate and simple analytic expressions for the characteristic wave resistance and the effective dielectric constant of the microstrip dipole antenna in the mixed dielectric medium have been derived. The theoretical values are in close agreement with the experimental results.     

Efficiency of resistive vee dipole antenna

The efficiency of the resistive vee dipole antenna, the arms of which are loaded with surface-mount chip resistors according to the modified Wu-King profile, is obtained numerically. The numerical model is based on the method of moments and validated by a set of reflection measurements. The numerical model is used to obtain the radiation efficiency and the power dissipated in each chip resistor. Results show that the antenna has low radiation efficiency because the chip resistors dissipate a significant portion of input power. The results may be used to determine the amount of input power that can be handled by the antenna or the resistor types that can handle the power required for a desired application.     

Pulse response of linear dipole antenna

Applications of transient electromagnetics include nonnuclear electromagnetic pulse (EMP) effects on electronic systems to evaluate system vulnerability. A basic component used in the mathematical modeling of systems for EMP vulnerability is the linear dipole antenna. Wu has derived an approximate analytical solution for the pulse reflected from the feed point of a linear dipole antenna for an incident ideal step function of current. The solution does not include the part associated with the very high frequency components because of an approximation used in evaluating the integral describing the reflected pulse. The approximation is eliminated and a simple analytical solution is given that describes that portion of the step function response associated with the very high frequency components. Numerical evaluation of the solution demonstrates convergence with Wu's approximate solution.     

Diode-loaded dipole antenna modeling and design

A circuit model for a diode-loaded dipole electric field measurement probe which is valid for frequencies below 10 GHz is presented. Assumptions are made to allow linear analysis based on the Laplace transform method. Optimized design criteria for the probe are then developed, with the major considerations being large bandwidth, independence of temperature, and maximum output. Experimental measurements on a probe designed for operation between 1 and 1000 MHz and comparison with the theoretical results are presented     

偶极子天线矩量法分析

基于矩量法对细直天线的电流分布及输入阻抗进行了分析，并与理论计算进行比较，结果表明：矩量法在计算较细的半波振子天线时，有较好的计算结果，对粗振子的结果误差比较大。     

Very wideband printed dipole antenna array

The design and experimental results of a very wideband small printed dipole antenna array are presented. The impedance bandwidth (VSWR ⩽1.7) of the antenna, centred at 780 MHz, is 47%. In the frequency band 610-960 MHz, the designed antenna has a gain of 9.5-11.9 dBi, sidelobe level <-16 dB and front-to-back ratio <30 dB. The main features of the design are the use of parasitic elements to expand the frequency band and the application of a mesh frame to decrease the sidelobe level     

Feed for dual-band printed dipole antenna

A dual-band printed dipole antenna is proposed for WLAN applications in the 2.4 and 5.2 GHz bands. A spur line was etched on the arms of the printed dipole to achieve the dual-band operation. The printed dipole antenna with a simplified matching network is proposed. The novel simplified feed structure consists of a pair of parallel metal strips printed on the opposite sides of the dielectric substrate and connected to a 50 /spl Omega/ microstrip line with a truncated ground plane. This feeding network does not require additional transition devices, such as a T-junction, power divider, tuning stub or microstrip-to-coplanar stripline balun.     

Ultra-wideband microstrip-fed planar elliptical dipole antenna

A small planar elliptical dipole antenna designed for ultra-wideband applications is proposed. With trimmed elliptical radiation patches and microstrip-coupled feeding structure, it exhibits excellent broadband behaviours and radiation patterns similar to those of a conventional dipole antenna. The simulated and measured results are in good agreement.     

FM wide band panel dipole antenna

It is very common that when a broadcaster needs to install an FM transmitting antenna within a large metropolitan area he places it on the tallest structure or building available. When the rooftop is already occupied by a large number of other types of transmitting and receiving antennas, the panel dipole antenna should be chosen. This antenna is secured to the side walls of the upper floors with the panel oriented to obtain full coverage of the most desirable areas of the city. For the Buenos Aires area this orientation avoids radiating toward Uruguay and specifically toward Montevideo, some 140 miles away. A wide band antenna operation permits placing the station on the air and at the same time allows future stations to share it without the installation of new antennas. Details of model and full model impedance and radiation pattern measurements during the antenna development are presented in order to show its technical characteristics. The radiation patterns were measured on a scale model in an anechoic chamber. The full scaled model was measured in an outdoor antenna range. Both E and H plane radiation patterns were measured along the FM band in order to observe pattern variations on both planes. Practically no difference in a panel radiation beamwidth from 88 to 108 MHz was observed and at the same time good input impedance was maintained. A really wide band antenna in pattern and VSWR is obtained. Power division for the antenna system is obtained designing an eight port power divider using the microstrip line technique. In this case, however due to high power operation the ground plane and strip are contained in a sealed metallic box and are separated by high pressure dry air like into the 3" feeding coaxial line.     

Electromagnetically coupled coaxial dipole array antenna

A new type of collinear antenna called electromagnetically coupled coaxial dipole array antenna is proposed. The antenna has an advantage of structural simplicity due to a novel use of an electromagnetically coupled feed structure for the radiating element. An analysis of the radiating element is presented and compared with experimental results. Fabrication and measurement of a prototype array antenna are also presented     

Transverse current on strip dipole antenna

The distribution of the current flow transverse to the axis of a small strip dipole antenna is evaluated numerically.