Impulse responses of two-dimensional antennas

On the basis of the equation of the Fresnel-Kirchhoff scalar diffraction field, the impulse responses of parallel-fed and series-fed rectangular antennas with separable aperture distributions and the impulse responses of parallel-fed and center-series-fed circular antennas with circularly symmetric distributions are derived—all of them can be expressed in the aperture amplitude distributions.     

Design of dual-reflector antennas with arbitrary phase and amplitude distributions

A synthesis method based on geometrical optics for designing a dual-reflector antenna system with an arbitrary phase and amplitude distribution in the aperture of the second reflector is presented. The first reflector may be illuminated by a pattern with an arbitrarily curved phase front. A pair of first-order ordinary nonlinear differential equations of the formdy/dx=f(x, y)are developed for the system. Questions concerning uniqueness, existence and bounds for the solutions can be answered. Calculations and numerical results for the design of a uniform amplitude and phase dual-reflector system are presented.     

Fast synthesis of aperture distributions for contoured beam reflector antennas

The use of a gradient function method to optimise aperture fields for contoured beam reflector antennas is shown to be efficient when compared with other approaches. A key feature of the method is that an analytical expression is used to modify the aperture distributions in each iteration.<>     

Reflector antennas with superquadric aperture boundaries

A unified treatment for reflector antennas with elliptical (circular) or rounded-rectangular (rounded-square) aperture boundaries utilizing superquadric functions is presented. Reflector antennas with superquadric aperture boundaries possess unique properties. To reveal these properties and properly implement them in diffraction analysis formulation, important geometrical features of the superquadric aperture, including a closed-form expression for the area, are presented. Parametric representations of the superquadric aperture are investigated, and a superior parameterization is introduced for evaluating the diffraction integrals. Representative results of physical optics (PO) analysis for superquadric reflector antennas are presented, and key features of the radiation pattern characteristics are summarized. Although the focus of this work is on reflector antennas, the main feature of superquadric aperture characteristics and its parametric representations are generally applicable to any aperture type antennas     

Synthesis of offset dual shaped subreflector antennas for control of Cassegrain aperture distributions

Many existing large ground reflector antennas have been designed as Cassegrain systems-i.e., paraboloid/hyperboloid combinations. Other large ground antennas are simply paraboloid designs. Upgrading the gain of these systems to a gain comparable to that obtainable with a dual shaped reflector antenna system has been an important and costly objective of many such ground stations. A potentially economic method for such an antenna upgrade is presented herein. It involves a redesign of only the subreflector portion of a Cassegrain antenna or the introduction of a subreflector feed system for a parabaloid. A pair of offset subreflectors are synthesized which will give a controllable high gain amplitude distribution in the aperture of the large paraboloid. The synthesis method that is used is based on an approximate formulation for an offset dual shaped high gain antenna that was first presented by Galindo-Israel and Mittra in 1977. In that approximate formulation, the geometrical optics (GO) energy was scattered from a subreflector and then from a second large reflector which reflected a uniform phase distribution. In the present offset dual shaped subreflector (DSS) antenna, the second reflection is from a smaller (sub) reflector and it scatters a spherical wave that feeds a hyperboloid or feeds a large paraboloid directly. Excellent results are shown for the approximate synthesis of the DSS.     

Multimode network analysis for dielectric leaky-wave antennas consisting of multilayer periodic structure with arbitrary dielectric distributions

The multimode network method is used to analyze the radiation characteristics of the leaky-wave antenna consisting of multilayer dielectric periodic structure with arbitrary dielectric distributions in each layer. The eigenfunction of each periodic layer is determined by Floquet theorem; and the mode matching combining with generalized transverse resonant method are used to derive the dispersion equation of the leaky-wave antenna. The complex transmission constant is calculated by Newton iterative method and the radiation characteristics of the antenna are obtained. Some antenna structures are analyzed and useful guidelines for design of the leaky-wave antennas are suggested.     

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…     

Analysis of cavity-backed aperture antennas with a dielectricoverlay

A full-wave analysis of cavity-backed aperture antennas with a dielectric overlay is presented. The theoretical approach uses a closed-form dyadic Green's function in the spectral domain. The aperture equivalent magnetic currents are obtained using the surface equivalence theorem and an integral equation is obtained by matching the fields across the aperture. The moment method applied in spectral domain analysis is employed to solve the integral equation for the equivalent magnetic currents with proper combination of subdomain or entire domain expansion functions. Numerical results include the aperture field distribution and antenna parameters such as input impedance, bandwidth, and efficiency. A set of measurements data is compared with results based on the theoretical work     

Phased array antennas with dielectric fin aperture loading

Planar waveguide array structures in which some form of dielectric matching is introduced, either in the form of a continuous sheet above the array face or dielectric plugs in the apertures, have received considerable attention in the literature. An alternative construction has one central dielectric fin or two edge dielectric fins in each rectangular waveguide aperture. Schaedla [2] has given a theoretical analysis for the first type of phased array but does not quote numerical results. In this paper computed results are compared with experimental measurements for simulated array faces of both types. Some conclusions are given regarding the comparative match-scan performance of fin-loaded, fully loaded, and empty waveguides. These results suggest certain advantages for the fin-loaded array configuration.     

Digital computer analysis of aperture antennas

Digital computer predictions of aperture antenna patterns are shown to be far more complete, in terms of information concerning the field vectors over virtually unrestricted angular sectors and even at short distances, when vector rather than scalar diffraction theory is applied.     

Transient field calculation of aperture antennas

The method of transient field calculation for large aperture antennas is proposed. It is shown that in the time domain, the calculation of the transient field is relatively simple for all points in the half-space in front of the aperture. The basic properties of the transient field are discussed     

Modal analysis of waveguide antennas with arbitrary cross sections

An approach is given to analyze the modal coupling of open-ended waveguides with arbitrary cross sections located in a conducting screen. The presented theory enables the determination of reflection characteristics of a single waveguide, as well as the analysis of mutual coupling between elements in waveguide antenna arrays. The field inside each waveguide is expressed as a sum of the transverse-electric and transverse-magnetic modes and expressions for the mutual admittances of modes excited at the aperture are obtained using a direct integration method. From these expressions, the mode reflection and conversion coefficients are determined. Computed and measured results are presented. Furthermore, this approach has been used to design a new type of horn antenna with high return loss and equal radiation patterns in the two principle planes     

天线孔径共用技术研究

提出了一种新的天线孔径共用的方法。在低频单圆锥天线的辐射非敏感区上加载高频段微带天线阵,可以将两个不同频段和极化的天线集成为一个天线孔径,该天线的体积质量与原低频段天线相当,天线的两个馈电端口集成在原单圆锥天线的地板上。利用电磁仿真软件HFSS分析了该共用孔径天线的性能,在双频段0.7~1.3 GHz和4.1~4.2 GHz内反射系数均小于–10 dB,两个端口之间的隔离度大于31 dB,辐射方向图低频段为全向,高频段为定向,4.15 GHz增益达到11 dBi,仿真结果验证了该孔径共用方法的可行性。     

Realisability of uniform aperture distributions

Physical realisability of uniform aperture distributions in planar-aperture antennas has been discussed in the light of Rhodes' interpretation of the volume integrals in the complex Poynting theorem.     

Improved coupling for aperture coupled microstrip antennas

Aperture shape and size are the crucial parameters for the aperture coupled microstrip antennas (ACMSA). A systematic comparision of various aperture shapes for the aperture coupled rectangular microstrip antenna has been carried out. An optimum “hour glass”-shaped aperture configuration has been proposed for maximum coupling     

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.<>     

Chiral slab polarization transformer for aperture antennas

The cross polarization of large aperture antennas can be eliminated by a chiral slab transformer in front of the aperture to obtain a more efficient field pattern. The inhomogeneous chirality distribution required can easily be achieved by using a mixture of right- and left-hand helices so that the total density of the helices is constant inside the slab. Reflection from the slab can be eliminated by a proper design     

Gaussian field expansions for large aperture antennas

An approximate theory of large aperture antennas is developed where aperture, Fresnel, and far fields are expressed in the form of Ganssian field expansions. First, aperture fields, i.e., aperture distributions, are expanded in orthogonal Hermite-Ganssian and Laguerre-Gaussian functions for antennas with rectangular and circular geometries, respectively. Then solution of the Fresnel-Kirchoff diffraction integrals yields the Fresnel and far field expansions. Care is taken to assure the direct transformability of the aperture fields. Optimal scale factors contained in the aperture field expansions are derived and lead to structured field distributions where sidelobes are added sequentially as more terms in the expansions are used in the computations. Tables of optimal scale factors and series coefficients are provided for cosine, truncated Ganssian and Taylor aperture distributions. Several examples are provided that demonstrate the usefulness of the formulas.