Dual-loop slot array antenna radiating circularly polarised wave

An array antenna consisting of dual-loop slot elements with a simple feeding system is realised. Each dual-loop element has two loop slots that are simultaneously fed by a single triplate transmission line. A narrowed beam, of circular polarisation, with an axial ratio of less than 3 dB, is obtained over a 3% bandwidth. The measured radiation pattern agrees well with a pattern calculated using array theory.<>     

Equivalent-circuit representation and characteristics of a radiating cylinder driven through a circumferential slot

The problem of an infinitely long coaxial cylinder with a single circumferential slot in the sheath is investigated analytically. When the slot width is small compared with the radius of the outer cylinder, an exact integral equation for the aperture field is formulated and subsequently solved by a quasi-static technique. Equivalent circuit representation of the coupling between the outside antenna and the inside coaxial line is obtained in closed form. Due to the highly localized nature of the coupling, the result thus obtained is applicable to finite cylindrical antenna with multiple feed slots.     

Miniaturisation of microstrip patch antenna using perturbation of radiating slot

A highly miniaturised rectangular microstrip patch antenna using deformation of the patch structure has been designed and fabricated at a frequency of 1.575 GHz (GPS). The fabricated antenna has a patch with an overall rectangular shape and depressed at its four corners (corner depressed microstrip patch antenna, CDMPA). In the linear polarisation, at a fixed rate of 1.2 of width/length (W/L), the CDMPA (53/spl times/63.6 mm) is reduced to 43.9% of the general plane type microstrip patch antenna (MPA, 80/spl times/96 mm) in patch size. The gain is 4.3 dBd which is lower than that of the general MPA (8 dBd) by 3.7 dB. In the circular polarisation, the patch size of the CDMPA (54.2/spl times/61.5 mm) is reduced to 52.8% of that of the MPA (76/spl times/83 mm). The axial ratio (AR) and axial ratio band width (ARBW) within 2 dB are 1.5 dB and 20 MHz (1.27%), respectively. The gain is 2.5 dBd, which is lower than that (4.2 dBd) of the general MPA by 1.7 dB.     

Admittance of a half-wavelength slot antenna radiating into a warm lossy two-layer plasma

The admittance of a half-wavelength slot antenna in a two-layer lossy plasma is shown to be greatly affected by moderate electron temperatures (T_{e} leq 1 eV) when the plasma is overdense. The effects of slot width and electron collision frequency upon the slot admittance also are investigated.     

Axial slot antenna on dielectric-coated elliptic cylinder

The radiation properties of an axial slot antenna on a conducting elliptic cylinder with a homogeneous dielectric coating are investigated. In the dielectric coating and in the exterior free-space region the field is expanded in elliptic waves using the Mathieu functions. The Mathieu angular functions are employed as basis and testing functions to enforce the boundary conditions at the interface between the dielectric and the free-space regions. The equations of continuity at the boundary are solved by Galerkin's method. Numerical results are presented in graphical form for the transverse electric (TE) and transverse magnetic (TM) polarizations to illustrate the far-field radiation patterns, the gain versus coating thickness, and the aperture conductance versus coating thickness     

The equivalent parameters for the radiating slot on a sectoralwaveguide

Formulas for the field components of the TE_pq, mode and the dominant mode TE₁₁ in a sectoral waveguide are given. Using the equivalence principle, the electric field distribution on the aperture surface of a narrow longitudinal slot cut in the curved broad wall of a sectoral waveguide is solved by the moment method (Galerkin's method). Important results such as the scattering parameters, the equivalent shunt admittance, and the resonant conductance and length are studied. The method used in this paper has good precision and has been adopted in the design of a linear slot array     

Effect of ground plane absorption coefficient on the admittance of a slot antenna radiating into a warm lossy plasma

The effects of the ground plane electron absorption coefficient on the admittance of a half-wavelength slot antenna radiating into a warm lossy plasma are examined for a range of plasma conditions and slot widths. The ground plane absorption coefficient is observed to have significant effects on the admittance of a thin slot when the plasma is greatly overdense, even when the plasma is only mildly warm (T_{e} leq 1 eV).     

Characterization and optimization of linearly tapered slot antenna pattern

A parametric study of linearly tapered slot antenna (LTSA) in air and a method for optimization of its pattern are presented. A method of moments code is utilized to investigate the behavior of LTSA’s as the length, height and the taper angle varies. It is shown that the antenna pattern can be improved using a top layer of dielectric material with varying permittivity.     

Multi-disk radiating structure with flat-topped element pattern forplanar array antenna

The results of numerical simulation and experimental modelling of a multi-disk slowing structure excited by a two-dimensional planar array antenna of circular waveguides are presented. The geometrical parameters of the array structure with the flat-topped element pattern, required to suppress the array grating lobes when beam scanning, are also determined     

Waveguide slot antenna with a coupled dipole above the slot

The effect of a parasitic dipole above a waveguide slot antenna is shown analytically and verified experimentally. The E-plane radiation pattern is shown to be rather sensitive to the change of dipole length, and an equalised E- and H-plane pattern is obtained by choosing a proper length of dipole.     

Synthesis of a slot radiator with a given radiation pattern

Synthesis of a slot cylindrical radiator with a given radiation pattern is studied. For a Gaussian pattern, the phenomenon of superdirectivity is analyzed and the parameters of the radiator providing for the optimal spread in the orders of the amplitudes of the currents on slots are estimated.     

Analysis of a slot microstrip antenna

The slot microstrip antenna is used as a folded slot dipole symmetrically fed across a gap by means of a strip line. A theoretical model equivalent to several lossy transmission lines had been described previously to explain the bandwidth and the radiation admittance. The theory is improved when coupling between the two equivalent radiating lines of every slot is taken into account, and explains a fourth resonance near the third one, which had been measured on several models. Theoretical results and experiments are in good agreement. They are radiation admittance in a wide frequency band, current distribution along each slot and radiation patterns.     

Analysis of a wide radiating slot in the ground plane of amicrostrip line

An analysis of a wide rectangular radiating slot excited by a microstrip line is described. Coupled integral equations are formulated to find the electric current distribution on the feed line and the electric field in the aperture. The solution is based on the method of moments and using the space domain Sommerfeld-type Green's function. The information about the input impedance or reflection coefficient is extracted from the electric current distribution on the microstrip line utilizing the matrix pencil technique. The theoretical analysis is described and data are presented and compared with other theoretical and experimental results     

一种小型宽频带缝隙天线的设计

设计一种结构新颖紧凑的小型宽频带(带宽10 GHz)微带天线。以24 mm×23 mm×1.6 mm的FR4为基底,在基底接地面中心位置设计一个正六边形和一个对称的十字交叉型贴片组成的缝隙来增大工作带宽,基底另一侧是一条微带线。用电磁仿真软件Ansoft HFSS对该天线进行模型仿真和结构优化,并进行加工和测试。结果显示该天线工作频段覆盖3.6～13.6 GHz,阻抗带宽为116%,辐射特性良好,给出了反射损失曲线和辐射方向图,测试结果与仿真结果基本相同,为宽频带无线通信的研究提供了一定的参考。     

非均匀网格FDTD分析波导宽边辐射缝隙特性

波导宽边辐射缝隙被广泛应用于波导缝隙阵列中，为了比较准确地对波导缝隙进行建模，同时考虑到计算资源限制，本文引入一种采用非均匀网格的时域有限差分方法对其S参数特性进行了计算。数值结果表明该方法分析波导辐射缝隙特性问题的有效性。     

A reflection cancelling slot set in a linearly polarized radialline slot antenna

A radial line slot antenna (RLSA) is a high-gain and high-efficiency planar antenna. A linearly polarized RLSA (LP-RLSA) is attractive for applications of various subscriber radio systems. However, the slot arrangement for linear polarization gives rise to serious reflection from slots, which disturbs the normal antenna operation. A new LP-RLSA slot design is presented where reflection canceling slots are added to the conventional ones; four slots form one slot set as a unit radiator of linear polarization. The experiments confirm the design: the antenna return-loss is improved from -2 to -10 dB. Antenna efficiencies of 48 and 54% are measured for 400 and 600-mmφ antennas, respectively. This is the first report of the normal operation of LP-RLSAs     

Iterative FEM for characterising radiating slot in broad wall ofrectangular waveguide

It is shown that the iterative finite element method with the radiation-type boundary condition can give an efficient and accurate solution to the radiation problem. The proposed method is applied to the characterisation of a radiating slot on the broad wall of a rectangular waveguide. The result is compared with those of other conventional methods, and shows a good agreement     

Analysis of the tapered slot antenna

A method for calculating the radiation pattern of end-fire tapered slot antennas with or without dielectric substrate is presented. The method involves a two-step procedure: 1) determine the field distribution of a traveling wave along the tapered slot, and 2) compute the radiation from this slot field by using the half-plane Green's function to account for termination effects. Acceptable estimates of the slot field usually can be obtained from a stepped approximation to the tapered geometry. The method has been verified by comparisons to measured patterns for various dielectric substrates and antenna dimensions. However, the effect of lateral truncation has not yet been successfully modeled. Experimental patterns showing this effect are presented.     

Analysis of a circular patch antenna radiating in a parallel-plateradial guide

This paper investigates the use of a coaxially fed patch as a feeding element in a single-layer radial line slot antenna (RLSA) array. A field matching method is described to analyze a recessed circular cavity radiating into a radial waveguide. Using the wall impedance approach, the analysis is divided into two separate problems of the cavity and its external environment. Based on this analysis, a computer algorithm is developed for determining wall admittances as seen at the edge of the patch in the cavity, the radial admittance matrix for the two-probe feed arrangement, and the input impedance as observed from the coaxial line feeding the cavity. This algorithm is tested against the general-purpose Hewlett-Packard finite-element high frequency structure simulator as well as against measured results. Good agreement in all considered cases is noted     

An equivalent circuit for the tee-fed slot antenna

In this paper an equivalent circuit is developed for a tee-fed slot antenna, and the equation describing its input impedance is derived. The input impedance for several antennas is computed and compared with experimentally obtained data.