Unidirectional antenna composed of dipole and loop

A new printed structure composed of a dipole and a loop antenna for achieving a unidirectional antenna is proposed. The proposed antenna demonstrates that when an electric dipole and a magnetic dipole are excited simultaneously, a unidirectional radiation pattern can be obtained. With the absence of any ground plane or reflector, this directional printed antenna with single-layer structure can be used nowadays in small directional wireless systems and some handheld devices that need to radiate in a particular direction. The antenna operates at 2.4 GHz with an impedance bandwidth of 7.4% for S₁₁ < -10 dB and a peak measured gain of around 4.3 dBi.     

On the magnetic dipole representation of small loop antenna

The use of a magnetic dipole to represent a small loop antenna is examined by comparing their field components. Particular attention is paid to the dipole approximation in the near field, and curves are presented which allow an accurate and rapid assessment to be made of the error as a function of angle and distance from the loop. The curves, which apply to any loop with a circumference between 0.0001 λ and 0.1 λ, enable the correction to the dipole field to be estimated. The difference between the loop and magnetic dipole fields is expressed algebraically for large distances from the loop, and for near-axial angles.     

Equivalent circuit of dipole antenna of arbitrary length

The purpose of this letter is to derive an equivalent circuit for a dipole of any length and to compare the input impedance versus frequency of the resulting equivalent circuit with published analytical and experimental data     

CPW fed active dipole antenna for television receivers

A coplanar waveguide fed active dipole antenna for a television receiver is fabricated on a thin dielectric film by using photoetching techniques. A transistor amplifier is integrated between the feeding point of the dipole and CPW. Actual gains of more than 8 dBd are obtained at frequencies from 470 to 770 MHz     

Asymmetric dipole antenna suitable for active RFID tags

A novel and simple antenna, which is designed for active RFID tags at 2.45 GHz, is proposed. The antenna, consisting of a short rectangle dipole and a bent 'T' shape monopole, is suitable for direct integration with electronic components such as batteries without significant antenna performance degeneration. Simulation and measurement results show that the proposed antenna provides good gain, excellent bandwidth and omndirectional radiation pattern.     

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.     

Resonant hemispherical dielectric antenna

An antenna consisting of a resonant dielectric hemisphere on top of a ground plane is investigated. Calculations of the internal and external fields are made with emphasis on the lowest-order mode that results in efficient radiation in the direction perpendicular to the ground plane. Measured input impedance data are also presented for a practical radiator.     

Symmetric electromagnetic field of a circular loop antenna over the conductive cone of finite length

The diffraction properties of the field of circular loop antenna over the conic surface of finite length have been investigated. The relationships of the radiated power as a function of the antenna position on the symmetry axis of the cone were established. The directional patterns and field distribution in the near-field zone were obtained for different geometrical parameters of the diffraction system. The results obtained were compared with similar relationships for semi-infinite cones.     

Quadrifilar loop antenna

A new quadrifilar antenna has been developed for generating circularly polarized backfire radiation. The antenna consists of two orthogonal rectangular conducting loops, each incorporating capacitive coupling and fed using either a single or two coaxial cables. Though the geometry is much simpler than a conventional quadrifilar helix antenna, the radiation pattern performance is very similar. Measured and simulated patterns are compared for two antennas with different feed arrangements. It is shown that the resonant structure can produce a cardioid pattern with a directivity of 4.5 dB (120/spl deg/ 3 dB beamwidth) and a front-to-back ratio of more than 20 dB at the center operating frequency. A 10% impedance bandwidth (VSWR<2) over which the axial ratio is less than 3 dB is demonstrated.     

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.     

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.     

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.     

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.     

对称振子阻抗特性分析

分析了求解对称振子输入阻抗的计算方法,包括近似方法(坡印廷矢量法、等效传输线法和感应电动势法)、解析方法(海伦积分法)和数值方法(矩量法),计算了不等长平行对称振子的互阻抗. 着重对等效传输线法和海伦积分法进行了分析和研究,对等效传输线法存在的不足进行了修正,推导了海伦积分法计算输入阻抗的各个参数,并将修正后的等效传输线法计算结果与海伦积分法和矩量法的计算结果进行了比较. 结果表明,修正后的计算方法适用于一般对称振子.     

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.     

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.     

Multi-circular loop monopole antenna

A novel multi-band multiple circular loop monopole antenna is presented. The three outer loops have a size ratio of 2 while the feed monopole is a disc, resulting in a quasi-log periodic performance. A method for controlling the radiation pattern, which gives better results than the circular disc monopole at higher operating frequencies, is presented. The proposed antenna performance is also compared with that of the fractal Sierpinski gasket monopole     

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