The effect of an offset impedance sheet on the admittance of a slot antenna

The effect of offsetting a plasma (or dielectric) from an infinite slot antenna excited with a TEM mode in a conducting plane is considered, using an impedance sheet as a model for the plasma. Results are obtained for the change in antenna admittance as a function of offset distance for several different values of plasma (dielectric) surface impedance and characteristic antenna dimensions.     

Computations of the aperture admittance of an axial slot on a dielectric coated cylinder

An extensive set of curves for the aperture admittance of a waveguide-fed axial slot on a coated metal cylinder is presented for both an underdense plasma and a Teflon coating. Examination of these curves shows that a slot on a cylinder with aKaof 2 to 3 has about the same aperture admittance as the identical slot opening onto a flat ground plane.     

X 波段加膜片式单脊波导裂缝天线的研究

等效导纳值是波导宽边纵缝天线的关键设计参数。为克服传统波导裂缝天线副瓣偏高、设计效率低下等问题,本文提出了一种单脊波导裂缝天线的改进设计方法,在传统波导裂缝阵列天线设计的基础上,利用等效导纳值对天线等效电路的影响,在裂缝单元下增加金属膜片,通过改变金属膜片的高度,优化裂缝等效导纳值,使得每个裂缝口径场分布更加接近于理论设计值,并在设计过程中使用牛顿迭代法提取导纳进一步缩短设计时间。通过设计实例表明:应用此方法设计单脊波导裂缝天线能够有效抑制副瓣电平,天线方位面副瓣电平可达到-30 dB 以下;在满足主要指标要求的前提下,设计效率显著提升。     

Improved coupling for aperture coupled microstrip antennas

An aperture shape that gives significantly improved coupling for an aperture coupled microstrip antenna is described. This 'dogbone' aperture consists of the usual rectangular slot augmented with loading slots at each end. Measured data show an increase of more than three for the resonant input impedance of an antenna using the dogbone-shaped aperture, as compared with the input impedance of the same antenna with a rectangular slot of the same overall length. The field distributions of both slots are also measured, and compared.<>     

The influence of air-gap tolerances on the admittance of a dielectric-coated slot antenna

The admittance of a TEM mode-excited parallel-plate aperture having an infinite flange and illuminating a displaced dielectric boundary is determined by the variational method. The results are applied to provide insight into the following two problems of interest: 1) the effect of an air gap on the admittance of dielectric-coated aperture antennas, and 2) the admittance of an aperture antenna coated with an underdense plasma slab. Numerical computations for the air-gap problem are verified experimentally.     

一种展宽波导缝隙阵列天线驻波带宽的新方法

辐射缝隙导纳和耦合缝隙阻抗的频率特性,是影响缝隙阵列天线驻波带宽的主要因素。以改善整个缝隙阵阻抗匹配频率特性为出发点,提出了一种展宽波导缝隙阵列天线驻波带宽的新方法,即选择合适的辐射缝隙的总导纳常数。仿真分析表明,改变后的缝隙阵列天线的驻波带宽有了较大改善,其与理论分析的结果是一致的。     

The input admittance of the rectangular cavity-backed slot antenna

The input admittance of the rectangular cavity-backed slot antenna is investigated. The slot is assumed narrow so that the voltage distribution in its aperture is sinusoidal. Equations which represent the input admittance of this slot, backed by a rectangular cavity in which a single propagating wave is assumed to exist, are given. Calculations based on these representations are compared to available measured data. As the depth of the cavity increased the resonant frequency decreased and the bandwidth became narrower. Input admittance curves as a function of electrical slot length are also presented for several size cavities.     

Calculation of external aperture admittance and radiation patternof a narrow slot cut across an edge of a sectoral cylinder in terms of aspectrum of two-dimensional solutions

A slotted triangular cylinder is a candidate for a base station antenna in mobile communications. This paper presents an analysis of the external aperture admittance and the radiation pattern of a transverse narrow slot cut across one of the wedges of a sectoral cylinder, the cross section of which approximates the actual triangular shape. Thereby, the external region can be described in terms of two canonical shapes, for which the dyadic Green's functions are obtained analytically. The aperture admittance of the slot is expressed in terms of the integrals of magnetic current over the slot aperture and the infinitely extended interface of the canonical regions. These integrals are evaluated in the spacial and spectral domains, respectively. This hybrid analysis provides good convergence of the results. The dependence of the 3-dB beamwidth and the front to back ratio of the transverse radiation pattern from the slot upon the size and the sector angle of the cylinder are also presented     

Admittance of a slot antenna following r.f. voltage breakdown

An experiment to determine the input admittance of a slot antenna after r.f. voltage breakdown outside the aperture has occurred is described. It is found that the conductance decreases and the susceptance increases with input-power level.     

Input impedance of aperture coupled hemispherical dielectric resonator antenna

A hemispherical dielectric resonator (DR) antenna fed by a microstripline through an aperture on the ground plane is investigated both theoretically and experimentally. The broadside TE/sub 111/ mode input impedance of the antenna configuration is evaluated, and reasonable agreement between theory and experiment is obtained. The effects of the slot length and the slot width on the input impedance are studied and discussed.<>     

Experimental study of the impedance of cavity-backed slot antennas

The impedance of a simple open slot antenna was measured as a function of frequency and was then compared with the theoretical values obtained through Babinet's principle from the known values of the admittance of its complementary antenna, the strip dipole. A careful experimental study was then made of the impedance of the same slot with several different cavity backings. The impedance was found both as a function of frequency and of the various parameters of the cavity, namely, the cross-sectional size of the cavity, the medium filling the cavity, and the type of termination of the cavity.     

Implementation and investigation of U-shaped aperture UWB antenna with dual band-notched characteristics

The design and analysis of an ultra-wideband (UWB) aperture antenna with dual band-notched characteristics are presented. The antenna consists of a circular exciting stub on the front side and a U-shaped aperture on the back ground plane. By inserting a slot and a parasitic strip to the antenna, dual notched frequency bands are achieved. A conceptual circuit model, which is based on the measured impedance of the proposed antenna, is also shown to investigate the dual band-notched characteristics. The measured impedance bandwidth defined by VSWR , 2 of 9.0 GHz (2.2?11.2 GHz), with the dual bands of 3.25?4.25 and 5.0?6.05 GHz notched, is obtained.     

Rectangular and zonal slots on a sphere with a backing shell: theory and experiment

A rectangular slot antenna on a spherical cavity with a conducting backing shell is investigated rigorously. The Green's function approach is used to formulate an integral equation for the magnetic slot current, which is solved using the moment method. Two previously developed methods to evaluate the admittance integrals are used and compared with each other. Both methods use recurrence formulas and analytical integration to speed the computation. The slot and cavity resonances of the structure are studied. In particular, two simple formulas for the first two natural resonances of the cavity structure are given. The effects of the shell size, slot length, and cavity dielectric constant on the input impedance are discussed. Measurements were carried out to verify the theory, and very good agreement between theory and experiment is obtained. In addition, the zonal slot antenna on a spherical cavity with a conducting backing shell is studied. The effect of the shell radius on the input impedance is investigated and, again, very good agreement between theory and experiment is found.     

一种小型陷波多用途超宽带天线

提出了一种小型陷波多用途超宽带微带天线。该天线与一般的宽缝隙微带天线类似,通过在矩形调谐支节上开V形缝隙获得了陷波特性。通过数值仿真和实验测量,对天线的阻抗特性、方向图和增益进行了研究。结果显示该天线在2.4到11GHz频段内驻波比小于2,在5.15~5.95 GHz范围内具有陷波特性。同时该天线还可覆盖2.4GHz无线局域网(WLAN)频段,在整个工作频段内有良好的辐射方向特性。     

Analysis of dielectric-resonator antennas with emphasis onhemispherical structures

An overview is given for the development of dielectric-resonator antennas. A detailed analysis and study of the hemispherical structure, excited by a coaxial probe or a slot aperture, is then given, using the dyadic Green's functions pertaining to an electric-current source or a magnetic-current source, located in a dielectric sphere. The integral equation for a hemispherical dielectric-resonator antenna (DRA), excited by either a coaxial probe or a slot aperture, is obtained. The integral equation is solved using the method of moments. The antenna characteristics, such as input impedance, radiation patterns, directivity, and efficiency, are computed numerically, around the resonant frequency of the TE₁₁₁ mode (the HEM₁₁ mode for cylindrical coordinates). The computed input impedance is compared with numerical and experimental data available in the literature     

Analysis of aperture-coupled microstrip antenna using thesegmentation method

The authors present an original analysis of an aperture-coupled microstrip antenna. The theory is based on the segmentation method, which considers the patch as a multiport network whose impedance matrix is deduced from a hybrid matrix, and the use of analytical expressions of the cavity admittance at the slot centre. The theory is presented for the first time, and the theoretical results are in good agreement with previous published measurements     

波导平板裂缝天线阵的设计

利用商业软件HFSS的S参数仿真结果,采用等效网络法对矩形波导宽边纵缝进行互耦环境下的导纳计算;并利用天线远场幅度、相位方向图仿真结果,采用口径场反演方法,对阵中辐射缝参数进行修正。通过设计实例,验证了该方法非常适合于平板裂缝天线阵的设计,有效地提高了设计效率。     

Dipole and slot elements and arrays on semi-infinite substrates

The printed dipole or slot antenna on a semi-infinite substrate and infinite phased arrays of these elements are investigated. The solution is based on the moment method in the Fourier transform domain. The generalized impedance or admittance matrix can be expressed in rapidly converging infinite-integral or infinite-summation forms, allowing the accurate determination of the current distributions. Using the present formulation, the input impedance, resonant length, and radiation pattern for the isolated antennas, and the reflection coefficient for infinite phased arrays, are calculated.     

The admittance of a parallel-plate waveguide aperture illuminating a metal sheet

The admittance of a parallel-plate waveguide aperture having an infinite flange and illuminating a metal sheet is determined by two separate methods: 1) wedge diffraction theory; 2) an integral transform solution. Numerical computations obtained by either method are in excellent agreement and are verified experimentally. A Smith chart is employed to show that, for a given aperture width, the admittance locus coalesces about the half-space value as the metal sheet recedes to infinity. A strong interaction between the aperture and the metal sheet occurs for distances in the vicinity of integral multiples of one half-wavelength. The interaction becomes much more localized with respect to distance as the distance to the sheet is increased; however, the admittance is always infinite at these distances.     

Flush mounted rectangular cavity slot antennas--Theory and design

The loaded rectangular cavity slot antenna is analyzed using variational methods in conjunction with simplified equivalent circuit techniques to derive accurate design guides for efficiency, bandwidth, and resonant frequency. The aperture admittance is computed and the effects of a compound aperture plane iris and of material loading are analyzed. The aperture admittance of all such loaded cavity antennas is proportional tomu_{r},sqrt{mu_{r}/epsilon_{r}}, or1/epsilon_{r}, which characteristic lends to a common method of optimization of|T|^{2}(transmission cofficient). Experimental results include: 1) measurements of aperture field; 2) a comparison of theoretical and experimental value of bandwidth, efficiency, resonant frequency, and beam pattern for several experimental models; and 3) the measurement of the effect of applied dc magnetic field.