Analysis of radiation from a horn with a superquadric aperture

This paper presents an analysis of radiation from a horn with a superquadric aperture, modeled using a cascade of superquadric waveguides. Electromagnetic fields within each waveguide are expressed in terms of a set of orthogonal modes derived from polynomial functions based on a Cartesian coordinate system. The scattering matrix at the horn aperture is obtained by calculating the scattering matrix at each of the waveguide junctions using mode matching, and cascading them appropriately. Radiation patterns corresponding to both x- and y-polarizations of the input excitation are then obtained by integrating the aperture field. The computed numerical results are validated by comparing them with the corresponding results obtained from measurements.     

High-frequency reflection from the aperture of a long E-planesectoral horn

The result of Yee et al. (1968) for the parallel-plane TE₁₀ -mode reflection coefficient, used in Jull's (1972) formulation for the reflection coefficient of a long E-plane sectoral horn, is replaced by the Boersma's (1974) corresponding result. At longer wavelengths, the expression that emerges displays a much better match with experiments than Jull's original expressions     

Omnidirectional s.h.f. antenna consisting of horn radiators and plane reflectors

A microwave transmitting antenna with omnidirectional pattern in the horizontal plane is described which consists of six horn radiators and six plane reflectors arranged in a hexagonal configuration. Each reflector illuminates an azimuthal sector of approximately 60°. If therefore, a sector-shaped horizontal pattern is required, less than six reflectors need to be provided.     

Reflection from the aperture of a longE-plane sectoral horn

The complex reflection coefficient of a longE-plane sectoral horn is derived using the geometrical theory of diffraction. Single diffraction alone is shown to be sufficient to describe the contribution from theE(widely separated) edges, while singly and doubly diffracted fields from theHedges are included by using an open waveguide result derived elsewhere. A relatively uncomplicated expression is obtained for the complex reflection coefficient of the horn which agrees well with experiment for horns with slant wall lengths greater than about3frac{1}{2}guide wavelengths.     

Design of rectangular horn arrays with oversized aperture elements

The possible existence of blind spots, due to forced aperture resonances, is demonstrated theoretically and experimentally at 14 GHz in rectangular grid arrays of tapered rectangular horn elements with oversized (overmoded) apertures. The dominant contributor to these blind spots is the resonance of the equivalent transverse magnetic (TM_12) waveguide mode. The numerical results based upon our approximate methods of formulation and solution of the array boundary value problem agree well with experiments. A method for eliminating the blind spots by proper taper design is presented and experimentally verified. The analytical methods used in this work could possibly be extended to conical horus and other tapered-structure arrays as well as other periodic grid geometries. New simple and accurate formulas for the zeros of Bessel and Legendre functions and their derivatives are obtained as a result of this analysis.     

Design of a plasma torch having a flame of oblong cross-section

A novel design of plasma torch is described, in which the flame cross-section has a major axis five times that of the minor axis. The ion number density has been measured and compared with that of the conventional torch with a flame of circular cross-section.     

On the fields in a conical horn having an arbitrary wall impedance

The electromagnetic fields propagating up a cone having an arbitrary wall impedance are found using an asymptotic solution. Three special cases are then considered: the smooth-metal wall, the corrugated wall, and the metal wall with a lossy-dielectric lining. The last case, in the form of an absorber-lining is then shown to behave like a corrugated horn since it too provides a highly taperedE-plane andH-plane aperture distribution. Furthermore, it does this over a much larger bandwidth, over 3:1, with negligible gain drop.     

An analysis of small aperture multimode horn as quasi-optical Gaussian beam radiator

In this paper a small aperture multimode horn is analysed by full-wave method and the coupling efficiency to Gaussian fundamental mode is calculated. The coupling efficiency of exceeding 0.98 is obtained over 4 GHz bandwidth. This horn may be used to connect waveguide with quasi-optical element in millimeter wave system and also may be used as an element in imaging array.     

Analysis of dielectrically loaded radiators using entire-domainGalerkin technique

The response of various types of dielectrically loaded radiators to a time-harmonic excitation is analyzed, by employing an integral-equation formulation in conjunction with an entire-domain Galerkin technique. Coupled integral equations are derived in the frequency domain. These are written in terms of the conductivity currents or/and the electric fields developed on the conducting surfaces or/and inside the dielectric materials, respectively. They are solved via the method-of-moments technique. In particular, an entire-domain Galerkin technique is employed, and proves very efficient, when rather specific geometries are considered and appropriate “intelligent” basis-function sets are chosen, accelerating the convergence of the method. To prove this claim, three representative antenna structures, of significant practical use, corresponding to the three types of geometries (cylindrical, spherical, and planar), are solved in the resonance region. Parallelization of the developed sequential code is employed, in order to extend the use of Galerkin technique to electrically large structures. The validity of the proposed method is checked, and numerical results are presented for several cases     

海上运动辐射源单站纯方位无源定位分析

针对海上运动辐射源单站纯方位无源定位过程中辐射源运动参数对定位性能的影响进行分析,提出利用对目标的航向分析改进定位性能的方法,分析其性能改善程度及局限性。     

复射线的平面口径辐射模型及其意义

复射线作为一种有效的数值计算方法得到了较广泛的研究和应用。但,复射线的复源点模型脱物理现实。而将复射线表示为一平面口径的辐射场,从而为复射线的发生提供了一种现实的物理模型－－平面口径辐射。在此基础上,对复射线的一些相关的问题进行了比较深入的讨论。     

Availability of a complex system having shelf-life of the components and common-cause failures

In this paper, a complex system comprised of two types of component is considered. Type I consists of N components connected in series, whereas type II consists of components connected in standby redundancy. It is assumed that a standby component may also fail in its shelf-life. Further, the system experiences two modes of failure—the first due to change in performance characteristics and the second due to a common cause. The availability of such a system is investigated using supplementary variable techniques and Laplace transforms. Finally, a number of interesting particular cases are discussed.     

Analysis of an infinite periodic array of slot radiators withdielectric loading

An efficient numerical procedure for determining the radiation characteristics of an infinite periodic array of slots in a conducting screen is presented. The procedure employs a novel mixed-potential integral equation formulation and is solved by the method of moments. Subdomain-type basis functions are used to provide the flexibility to model arbitrarily shaped slots. Analysis is carried out to account for dielectric layers, ground planes, or cavities placed on either side of the slot. Series acceleration techniques are employed to reduce significantly the computation time required to sum the series representing the periodic Green's function. The numerical scheme developed is applied to obtain quantities such as the slot field distribution and input admittance as a function of the array scan angle. Where possible, numerical results obtained are compared with data available in the literature. Data for the half-space case are found to agree with those of A.Y. Grinev et al. (1978) except for the case of multilayer dielectric loading     

A novel horn radiator with high aperture efficiency and low cross-polarization and applications in arrays and multibeam reflector antennas

A step horn structure is presented that yields about 90% aperture efficiency with low cross-polar radiation. It is found that for obtaining high aperture efficiency, the horn aperture should consist of only the TE/sub z/ type of modes in appropriate amplitudes and phases. The desired TE/sub z/ modes are produced using multiple steps in the horn walls. The distances between the steps are critical to suppress the undesired TM/sub z/ modes. Radiation characteristics of high efficiency circular and square horns are presented and potential applications of such high efficiency horns are discussed.     

Hankel transform domain analysis of complex resonant frequencies of double-tuned circular disc microstrip resonators/radiators

An exact analysis of double-tuned circular disc resonators/radiators is described. This method is based on the Hankel transform domain analysis and is numerically quite efficient. Several numerical examples are compared with available experimental data.     

Analysis of electric quadrupole radiation in the time domain: application to large-current radiators

In this paper, the fields created by a hertzian electric quadrupole fed by a non-sinusoidal signal are analysed in the time domain. The results are compared with those obtained for an electric dipole and are applied to the study of the field created by the practical antenna, the large-current radiator.     

Fields of linear radiators in the near-field zone

The mutual effect of electric dipoles that are close to each other is analyzed in the near-field zone. The input impedances, currents and fields of the radiators are calculated. The method for the calculation of the system of two radiators is based on the theory of folded dipoles. The fields of application of the closely lying radiators are presented.     

Domain decomposition FDTD algorithm for the analysis of a new type of E-plane sectorial horn with aperture field distribution optimization

In this paper, a universal and efficient approach of domain decomposition finite-difference time-domain FDTD (DD-FDTD) is presented for the analysis of a new type of horn antenna-E-plane sectorial horn with field amplitude taper and phase correction in the aperture. The power fed into the horn is redistributed to achieve the optimal field amplitude distribution in the aperture, and meanwhile the field phase is corrected by metal lens. Compared with conventional E-plane sectorial horns, the new horn antenna takes the advantages of low sidelobe level, short physical length and wide flare angle etc. Moreover, the most important property of this horn is the weak coupling with each other when it is used as the element of a phased array antenna. The field analysis of such a horn antenna is an extremely complicated three-dimensional EM boundary value problem. The domain decomposition FDTD method is presented in this paper to break through the drawback. The whole horn is decomposed into several subdomains and the meshes are created in local coordinates. In the iteration procedure of FDTD, the data are exchanged between adjacent subdomains with overlapped meshes. The aperture field distribution, voltage standing-wave ratio and pattern calculated by the DD-FDTD method are in good agreement with the experimental data.     

Analytical form of EM fields radiated by circular aperture antennas of various current distributions

~~Analytical form of EM fields radiated by circular aperture antennas of various current distributions[1] Schelkunoff S. A., Advanced Antenna Theory, John Wiley &Sons, 1952. [2] E|liott R.S., Antenna Theory and Design, Prentice-Hall, Engie-wood Cliffs, N J, 1981. [3] R.W.P. King and G.S. Smith, Antennas in Matter: fundamen-tals, Theory and Applications, MIT Press, Cambirdge, MA,1981. [4] W.L. Stutzman and G.A. Thiele, Antenna Theory and Desigrn,John Wiley & S…     

相干编码成像分析及其仿真研究

相干编码成像技术是近年来受到广泛关注的一项主动成像技术.它利用直线下涉条纹对目标的频谱进行提取,并利用相位闭合技术消除随机相位,最终获取远距离目标的高分辨率图像.文章对傅里叶望远术的基本理论进行了推导,详细阐述了相位闭合实现方法,并对各个过程进行了计算机模拟,使得能在实验条件不太成熟的情况下对它的理论进行实践.仿真实现了对两个目标的频谱扫描并重建了它们的二维灰度图像,充分验证了傅里叶望远术的正确性和可行性.