Analysis Of Radiation Patterns Research Articles

Radiation Pattern Analysis of Antenna Systems for MIMO and Diversity Configurations

Abstract. Multiple-input multiple-output (MIMO) antenna systems and antenna configurations for wideband multimode diversity rank among the emerging key technologies in next generation wireless communication systems. The analysis of such transmission systems usually neglects the influences of real antenna radiation characteristics as well as the influences of mutual coupling in a multielement antenna arrangement. Nevertheless, to achieve a detailed description of diversity gain and channel capacity by using several transmit- and receive antennas in a wireless link, it is essential to take all those effects into account. The expansion of the radiation fields in terms of spherical eigenmodes allows an analytical description of the antenna radiation characteristics and accounts for all the coupling effects in multielement antenna configurations. Therefore the radiation pattern analysis by spherical eigenmode expansion provides an efficient alternative to establish an analytical approach in the calculation of envelope correlation or channel capacity.

Aircraft antenna coupling minimization using genetic algorithms and approximations

Genetic algorithms (GAs) are used to minimize antenna coupling by optimally positioning multiple radiators. Initial GA parameters are selected using a simple cylindrical model, and the results are used to optimize antenna placement on a realistic aircraft surface model. A novel aggregate objective function incorporating surface wave coupling, variance of the coupling values, and radiation pattern analysis is used. Multiple computational and experimental data are shown to validate the methodology.

Effect of amplitude tapering and frequency-dependent phase errors on radiation characteristics of radial waveguide fed non-resonant array antenna

A high-gain low sidelobe level array antenna that is fed by a radial waveguide and designed to operate over a frequency range is considered. Assuming azimuthally symmetric excitation, the radiation pattern of the circular array is approximated by the space factor for the equivalent circular aperture and a simple and efficient tool is introduced for analysis of the array radiation pattern. The effect of the tapering, for both paraboloidal and bell-shaped aperture amplitude distributions, and the consequences of the phase errors, caused by the variation with frequency of the electrical lengths in the radial waveguide feed structure, on the gain and sidelobe level are studied in detail. Results obtained based on the proposed analysis are validated with respect to experimental data available in the literature. They are applicable to designs of arrays as well as aperture antennas.

Feed array synthesis for reflector antennas in contoured beam applications via an efficient and novel Gaussian beam technique

A relatively rapid procedure is developed, which combines a novel Gaussian beam approach for the fast analysis of reflector antenna radiation patterns with an iterative optimization method, to synthesize feed array distributions for parabolic reflectors in contoured beam applications. Here, relatively few Gaussian beams are employed as electromagnetic basis functions to represent the field radiated by the feed array in a highly efficient manner. Closed form expressions are used to find the reflection and diffraction of each of these Gaussian beams when they are incident on the parabolic reflector after they are launched from appropriate locations on the feed array plane. The coefficients (or initial launching amplitudes) of the Gaussian beams used in this expansion for the radiation from the feed array are found via an efficient iterative optimization procedure based on the method of successive projections. These coefficients are then directly related to the strengths of the array element source distributions (or array weights). Numerical examples of practical interest are presented to illustrate the utility and the speed of the present approach, which is found to be substantially faster than conventional approaches for these cases.

Analysis of Radiation Pattern of Radar Systems Based on Leaky Coaxial Cables

Theoretical and numerical analyses of the radiation directivity of a guided radar system based on leaky coaxial cable (LCC) are presented both for buried and open installations in clutter conditions. The theoretical model of fields generated by a cable buried in a lossy half-space, such as a sub-soil medium, is introduced to describe the working characteristics of such a leaky coaxial cable. The interactions of two modes, external and internal, which determine the coupling effect between an LCC and the environment, is analysed to predict the overall sensitivity and field pattern of such a radar system. It is shown that the coupling is the measure of the signal accessibility at a given radial distance outside the cable and it is very dependent on the particular installation and environmental aspects. A numerical technique, which describes various kinds of LCC installations and can predict the effective characteristics of a radar system based on an LCC with the required parameters including its directional properties, is proposed to analyze the clutter effects and to optimize the sensitivity of such a radar system both for open and buried installations. The distribution of radiation around the cable is examined numerically for the LCC buried at depth d in a sub-soil medium, as well as for an open installation near different kinds of wall. The radiation pattern of such a radar system across the cable system for both kinds of installation is investigated.

Antenna radiation pattern analysis using spherical near fields and the uniform geometrical theory of diffraction

A new method is developed for antenna radiation pattern analysis using spherical near fields and the uniform geometrical theory of diffraction (UTD). The spherically scanned tangential electric near field is transformed to the present one to more efficiently obtain the far-field antenna pattern by employing UTD. Examples illustrating the accuracy and speed of the method presented in this paper for large antennas are presented. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 21: 390–392, 1999.

Antenna radiation pattern analysis using spherical near fields and the uniform geometrical theory of diffraction

Antenna radiation pattern analysis using spherical near fields and the uniform geometrical theory of diffraction

Antenna radiation pattern analysis using spherical near fields and the uniform geometrical theory of diffraction

Antenna radiation pattern analysis using spherical near fields and the uniform geometrical theory of diffraction

Effect of Fracture Dynamics in Thin Plate on the Waveform and Radiation Pattern of the Lamb Waves

Since the acoustic emission (AE) due to fractures in thin-wall structures is monitored as Lamb waves, advanced signal analyses are required for evaluation. The present study aims to estimate the fracture kinematics (crack normal and displacement discontinuity vectors) in thin plates by radiation pattern analysis of the zeroth-order symmetric Lamb waves (S0-Lamb). We monitored in-plane profiles of the S0-amplitudes and polarities produced by six types of surface and buried Mode-I, II and mixed-mode fractures simulated with a line pulse laser and slender piezo-elactric Pb(Zr-Ti)O3 (PZT) elements. The Mode-I fracture showed an elliptical amplitude profile with the largest amplitude in the crack-opening direction, while the mixed-mode fracture as well the Mode-II fracture showed a connected rugby-ball-shaped pattern, or a two-quadrant profile of S0-polarities with the largest amplitude in the displacement discontinuity direction. The radiation pattern was demonstrated to be utilizable for estimating the fracture kinematics. For studying the fracture kinetic or crack generation velocity, we determined the overall transfer function of the system by the Gauss-Zeidel deconvolution of the wave generated by PZT elements whose out-of-plane displacement was measured using a laser interferometer. The source dynamics (kinematics and kinetics) of hydrogen-induced blistering (HIB) in a ferritic steel plate was estimated by radiation pattern analysis and source simulation. HIB was found to be caused by surface-normal cleavage fracture with source rise times from 0.6 to 1.0 µs. The estimated crack size agreed fairly well with the postmortem blister size.

Computer aided design algorithm for singly fed circularly polarized rectangular microstrip patch antennas

Based on a resonant cavity model, this work presents an effective computer aided design (CAD) algorithm to design singly fed circularly polarized (CP) rectangular microstrip patch antennas. The CAD algorithm allows precise prediction of the antenna performance. The analysis of radiation pattern, input impedance, and axial ratio parameters confirm the success of the design. The experimental results from a manufactured prototype operating at 2.25 GHz are in good agreement with the CAD predictions. ©1999 John Wiley & Sons, Inc. Int J RF and Microwave CAE 9: 32–41, 1999.

Design and analysis of multiple-beam reflector antennas

Simplified design and analysis equations are presented for multiple-beam reflector antennas based on the Gaussian-beam analysis of the primary and secondary patterns. The derived equations are useful for the quick design and performance analysis in terms of the coverage-area directivity and the inter-beam isolation of multiple-beam antenna systems. Results of the analysis given in this paper agree well with rigorous computations based on physical-optics analysis of the reflector-antenna radiation patterns. Extension of the analysis to multiple-beam lens antennas, and to shaped/contoured-beam antennas, is also presented.

Effect of Glass Fiber/Matrix Interfacial Quality on the Dynamics of Microfractures in GFRP. (1st Reports, AE Source Simulation Method and Acoustic Properties of UD-GFRP.)

With the aim of studying the effect of glass fiber/matrix interfacial quality on the dynamics of microfractures in GFRP, we propose a new source simulation of dissipative elastic waves. We measured the out-of-plane displacements by the longitudinal wave(P-wave)using a developed AE monitoring system and computed them by the convolution integral of assumed fracture dynamics with the analytical transfer function of the medium(Green' function of the second kind), by taking into account both the orientation dependence of velocity and attenuation of the P-wave. We also propose a new computer algorithm for estimating the source locations and fracture modes by using the arrival time and radiation pattern analysis of the P-wave. The first report introduces the proposed AE source characterization algorithm and acoustic properties of an unidirectional GFRP. Macroscopic elastic properties of UD-GFRPs with different interfacial qualities prepared by adding a small amount of paraffin wax are also reported in this paper.

Cylindrical Transform Technique for Radiation Pattern Analysis of Wraparound Microstrip Antenna on Cylindrical Body

The paper describes radiation characteristics of wraparound microstrip antennas on dielectric coated conducting cylinder. The effects of the finite length and radius of conducting cylinder, permittivity and thickness of the dielectric substrate and frequency on the radiation pattern are investigated. Initially the radiated near-fields are determined from the equivalent magnetic ring current sources, which arise due to fringing Fields at the edges of the patch. These fields are determined from the cavity model. The presence of the dielectric layer, strip conductor and the metallic body are taken into account in the radiation pattern analysis by the use of three dimensional cylindrical wave transform of the radiated nearfields.

Nonparaxial analysis of the far-field radiation patterns of double-heterostructure lasers

Previous analytical approximations for the far-field radiation patterns of a double-heterostructure laser have been restricted by TE-mode propagation in slab waveguides. A model that is applicable to both TE- and TM-mode propagation either in a slab waveguide or in a multiple-quantum-well structure is developed. Results of computations agree with the measured irradiance profiles of visible diode lasers of wavelengths from 635 to 670 nm. A process for deriving far-field expressions in terms of the diode-laser parameters listed in data books is suggested. Astigmatic aberration present in the wave front is determined, and the final result is expressed in a form convenient for diffraction analysis of truncated focused (or collimated) diode-laser beams.

アコースティック・エミッションの放射形式計測によるアングルプライＣＦＲＰ積層板の微視割れモード評価

A new acoustic emission (AE) analysis method for fiber reinforced composite material was developed. Phase combinations of first arrival quasi-longitudinal wave of AE in plate (Lamb wave) was analyzed based on AE spherical radiation pattern in infinite homogeneous medium, plate wave propagation properties and detection properties of piezoelectric AE sensor. Angle ply carbon fiber/epoxy composites were prepared to the AE and Ultrasonic C-scope tests to evaluate the fracture processes of delamination. Three stages characterized both the compliance and the AE properties were observed during tensile tests. The spherical AE radiation pattern analysis could distinguish into three types of fracture mode for detected AE events, such as tensile fracture, shear fracture and mixture fracture of tensile and shear. By analyzing the AE spherical pattern events, C-scope, surface and fracture surface observation, fracture processes of the angle ply CFRP were proved. At stage I of which is linear load-strain region, debondings occurred at notch tip along the fiber orientation of each layer as shear fracture. At stage II of which is transient region between stage I and III, coalescence of the debonding in each layer occurred as tensile fracture. At stage III of which is heavy increase of the compliance and the AE counts region, the debonding and the coalescence occurred at the same time along the fiber orientation.

E-plane analysis of a modified horn antenna with suppressed far-out sidelobe level

It is shown that the far-out sidelobes of a horn antenna can be suppressed by curving the edges in the aperture. A three-dimensional uniform geometrical theory of diffraction (UTD) analysis of the E-plane radiation pattern of the modified horn antenna was performed and compared with straight edges. This analysis indicates that the curvature of the edges does indeed influence the sidelobes to the effect that the modified horn antenna has significantly lower far-out sidelobes. The radiation patterns for modified horns were measured and compared with the calculated patterns and were found to be in good agreement.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

ACOUSTIC EMISSION EVALUATION OF FIBER REINFORCED PLASTICS (FRP) COMPOSITE The In-plane Statistical Radiation Pattern Analysis

Abstract The in-plain statistical acoustic emission radiation pattern analysis on fiber reinfected composite material is successfully developed. The method is based on both the analysis of the displacement field of Lamb wave and evaluation for the sensitivity of piezo-electric device properties. The sample of the test used is angle ply CFRP. The acoustic emission signal detected using special six piezo-electric resonant sensors developed in our laboratory. Signals from the sensors are acquired using two different systems, PAC 3000/3104 AE analyzer and Dynamic Crack Microscope, which is a six channel acoustic emission source characterization system developed in our laboratory. The fracture mechanisms of this sample consists of Mode I, which corresponds to the delamination, Mode II which corresponds to debonding, and Mode I and Mode II combined mode which corresponds to a continuous delamination.

Radiation pattern analysis of arbitrary wire antennas using spherical mode expansions with vector coefficients

A spherical mode expansion with Cartesian vector coefficients is presented for the study of the radiation patterns of arbitrary wire antennas. Coefficients are obtained by using a spherical harmonic series for the free space Green's function in conjunction with the current distribution obtained with the method of moments. Transverse components of the far field are ultimately obtained yielding a compact pattern representation suitable for rapid retrieval and display. The length of the expansion is shown to be related to the precision specified for the pattern; i.e., more precision requires more terms. A useful truncation criterion is proposed and verified by comparing results obtained for several typical wire antennas. >

Radiation pattern analysis of an antenna mounted on a finite ground plane with a dielectric coating

AbstractThe airborne antenna may be considered to be small since it is mounted on a conductor which is large compared to the wavelength and its radiation pattern has to include the diffracted fields from the conductor. Moreover, thick dielectric coating on the body, which is used as insulating material, causes a serious distortion of the radiation pattern; and this is confirmed through measurements that the effect is quite large.This paper proposes a method of analysis where the effect of dielectric material on the radiation pattern is estimated analytically using a simple plane conductor model. Analysis is based on the excitation of the surface wave which propagates inside the dielectric sheet and making assumptions about the radiation mechanism, its diffracted field is calculated by the uniform theory of diffraction (UTD) method. The availability of this method of analysis was confirmed by comparing the measured results of this model with the calculated values. From the measured and analytical results, it was confirmed that a large effect is produced in the axially back direction of the rocket due to dielectric coating on the body.

Geometrical theory of diffraction including corner diffractions with application to radiation pattern analysis of major angle corner reflector antenna

AbstractThe major angle corner reflector antenna is characterized by a large half‐power value width in the magnetic plane and a large front‐to‐back ratio. This antenna is considered a candidate for the fixed‐state antenna for radio communication within a limited space being studied by the authors. The analysis of radiation patterns of antennas of this type traditionally has been carried out by the induced electromotive force (EMF) method. In such calculations, the errors in the sidelobes have been substantial.In the analysis of the radiation pattern in this paper, the corner diffraction formula derived previously and the approximate corner diffraction formula for a hollow wedge corner which is newly derived by an asymptotic calculation from the equivalent edge electric and magnetic currents in the UTD are included in the application of the GTD (Geometric Theory of Diffraction). It is shown that by this approach an accurate analysis can be performed in both the E‐ and H‐planes. It is confirmed that the results by the GTD, by the MM (moment method), and by the experiments agree well.