Scanning of sector and cosecant beams generated by a circular aperture

A method of scanning a one-dimensional shaped pattern generated by a circular aperture is presented. It is shown that the desired beam shape can be retained in the desired scan plane by superposing on the nonlinear phase distribution applied along and parallel to the meridian plane, a linear phase progression along the perpendicular direction. Analysis carried out using the stationary phase method of evaluating the integral reveals that the gradient of the linear phase progression is a function of position along the meridian plane of the aperture. Expressions for the phase functions are derived. Computed results on the phase distribution and the radiation pattern are presented.     

Generation of cosecant beams from circular arrays

The generation of shaped beams from circular aperture is reported by Chakraborty et al. However there is no data available on the shaped beams from circular arrays. As the circular arrays exist in practice, they are designed to produce shaped beams. A new amplitude distribution is proposed and the concept of energy relations and stationary phase are used to design the optimized phase distribution. Introducing the phase function so obtained the patterns are realized and compared with those of specified. The cosecant beams are generated from small and large circular arrays.     

A planar slot array with four independent beams

Active Doppler velocity sensors require an antenna system that generates three or more independent beams. A four-port dual-mode antenna that generates four independent beams from a single aperture is described. The signals emanating from the four ports generate four beams in space through a common aperture of crossed slot radiators. Isolation between the four signals processed through the antenna is obtained primarily by utilizing the mode isolation that exists between theTE_{10}andTE_{01}modes in square waveguide. The isolation obtained between ports was 27.5 dB or greater. The special design problems and the effect of dimensional tolerances on the port isolation are discussed. A gain of greater than 30 dB for each beam and an overall antenna efficiency of approximately 71 percent were achieved. The beam pointing directions ranged from 27 to 29 degrees from the normal to the aperture. Sidelobes of 15 dB or better were also obtained.     

A reflection array of loaded microstrip radiators

A planar reflection array consisting of a primary radiator and an array of secondary microstrip radiators such that the phases of the fields generated by these radiators are identical in the direction of radiation is considered. This identity is attained by means of a forced phase step of the reradiated field. An approximate method for calculating the phase step of the reflected field relative to the phase of the incident field that arises during reradiation of the incident signal by an element of the reflection array is proposed. The method is based on the theory of dipoles and the reciprocity theorem. Dependences of the phase step on the dimensions of the antenna and the reactive stub, as well as the capacitance of the capacitor formed by the slot cut in the antenna, are studied. The calculation method is extended to the case of a two-stack microstrip antenna. A method is proposed for setting the maximum of the radiation pattern of this reflection array in a specified direction via the use of an electric signal to control the capacitances of the capacitors in the array elements.     

An array of coupled nonradiative dielectric waveguide radiators

A novel antenna array that radiates a single mode of multiple coupled nonradiative dielectric (NRD) waveguides, is described. The array is fed by a single NRD waveguide, which is designed to propagate a wave with the same wave number as that of free-space. The individual radiators of the array are spaced at one free-space wavelength, but due to the narrow beamwidth of the individual radiators, grating lobes are effectively suppressed. An eight-element array is described and measurements presented, but the design method can be extended to any number of elements     

Infinite planar arrays of arbitrarily bent thin wire radiators

A plane wave expansion moment method is presented for computing active impedances and current distributions of infinite planar arrays of thin wire radiating elements. The array lattices can be rectangular or triangular. The excitations can be plane waves or progressively phased voltage sources. Each radiating element, including feedline, can be any collection of bent thin wires. Results are given for arrays of straight dipoles with straight feedlines, straight dipoles with bent feedlines, and swept back dipoles (arms inclined with respect to the array planes) with straight feedlines. The experimentally observed phenomenon of array blindness as a consequence of feedline scattering is verified theoretically. The absence of this effect when the dipole arms are inclined with respect to the array plane also is verified.     

高斯光束通过倾斜光学元件的变换特性

基于广义惠更斯菲涅耳衍射积分,对高斯光束通过倾斜透镜后的传输特性作了研究,推导出了它的传输方程,并与离轴高斯光束通过透镜的变换做了比较,得到一些有意义的结果,以M2因子和桶中功率为参数分析了偏轴高斯光束的光束质量。     

Experimental millimetric array using dielectric radiators fed by means of dielectric waveguide

A millimetric array is described which employs dielectric radiating elements excited by means of a dielectric waveguide. The design of the array is developed using the method of effective dielectric constants and a simple array theory. Measurements performed on a nonresonant prototype demonstrate its feasibility and its potential for frequency-scanning applications.     

A MATLAB-based visualization package for planar arrays of isotropic radiators

This article introduces a simple MATLAB antenna package (ANTEN/spl I.bar/GUI) for the visualization of the radiation patterns, beamforming, and beam-steering capabilities of user-designed planar arrays of isotropic radiators. The package can be used as an educational aid, especially in antennas and propagation lectures.     

Wide-angle impedance matching of a planar array antenna by a dielectric sheet

For wide-angle scanning array antennas, the magnitude of the reflection changes substantially with scan angle and wave polarization. Conventional matching techniques in the individual element feed lines cannot compensate for these changes. There is a method of wide-angle impedance matching (WAIM) which utilizes a thin, high-k, dielectric sheet spaced in front of the array. It is capable of equalizing the reflection coefficient forEandHpolarization at any specified scan angle, or for any angle in theEandHscan planes. This technique is applied to an array having element aperture windows flush with a metal face. It is adapted for the procedure of matching in a waveguide simulation of an infinite array.     

Properties of electromagnetic beams generated by ultra-widebandwidth pulse-driven arrays

Analytical bounds on the characteristics of beams generated by an arbitrary pulse-driven array are derived and supported with numerical calculations. These bounds extend the meaning of near-field distances or diffraction lengths to the situation where the array driving functions can be broad-bandwidth signals. Particular attention is given to transmitting and receiving array systems which consist of elements that are not large in comparison to the shortest wavelength of significance contained in the signals driving them. Their output signals constitute higher-order beams whose coherence properties are degraded more slowly by diffraction than lower-order beams. It is shown that for certain measures of performance involving these beam characteristics, a localized wave pulse-driven array can outperform similar continuous-wave-driven arrays. An array with independent addressable elements is required to realize these localized wave effects. The enhanced localization effects are intimately coupled to the proper spatial distribution of broad-bandwidth signals driving the array     

Near-field coherent source localization by planar array design

This paper is concerned with near-field source localization for scenarios where coherent narrowband sources exist. In this paper, we propose a new method in which we design a general planar array with a covariance matrix whose rank is not decreased by the coherence between sources. Moreover, conditions for the sensor locations in the designed planar array are derived to reach maximum effective array aperture. The proposed method uses second order statistics and features a separable range-bearing search to reduce the computational complexity. This method localizes near-field sources with a number of one-dimensional searches in two steps. In the first step, ranges of sources is estimated using one 1D search and in the second step, the bearing of each signal source is estimated using the corresponding range estimated in the first step. Simulation results show that the performance of the proposed method is comparable with the Cramer–Rao bound.

     

Compensation of spherical reflector aberrations by planar array feeds

The feasibility of correcting phase aberrations of spherical reflector antennas with planar array feeds has been investigated. This type of feed seems to be particularly attractive for applications requiring several closely spaced beams. A synthesis procedure for the array excitation has been developed which minimizes the mean-square error with respect to a prescribed reflector illumination. This method was applied to the analysis of a spherical reflector antenna with a642lambdadiameter and an effectiveFnumber of 0.9.     

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     

Four independent beams from a single linear array

This paper describes an antenna technique which combines the dual-mode operation of a radiating square waveguide transmission line with the attachment of multiple ports to produce an antenna which can generate multiple, independent beams in space. The technique can be used to simultaneously transmit or receive signals through the beams with considerable isolation (>37 dB) between several of the ports. By this technique a single, traveling-wave-operated, linear array was designed to generate four unique beams in space. The beams consisted of two pairs of image beams which were produced by the use of an even coupling function design in the aperture. Measurements made of the array model atX-band showed good agreement with theory.     

Properties of a nonisosceles triangular grid planar phased array

An array with a general triangular grid structure (not necessarily isosceles) is considered, and methods of generating such an array are described. An analysis of its properties is presented. It is shown that this array has a grating lobe of -6 dB relative to the main lobe. The necessary conditions to avoid grating lobes are presented, with the conventional rectangular and isosceles triangular grids included as special cases. Furthermore, it is shown that one of the grid dimensions can be extended as compared to that of an isosceles triangular grid. However, when this is done, the optimal, grid area is reduced.     

一种多波束面阵天线的分析与设计

介绍了二维多波束天线的特点和实现二维多波束的几种方法，针对空馈的Rotman透镜推导出了由它馈电的平面天线阵的相位计算公式及设计方法，在此基础上成功地实现了空馈透镜的平面天线阵样机，并给出了相应的测试结果。     

Mutual coupling analysis of a finite planar waveguide array

This paper deals with mutual coupling in a finite planar array antenna, composed of open-ended circular waveguides in a ground plane. The element-by-element approach is used and the problem is formulated as an integral equation, by requiring the transverse electric and magnetic fields to be continuous across the apertures. The equation is then solved by the method of moments and the mutual coupling in a 127-element array is computed. Excellent agreement with measurements and with the active reflection coefficient for the corresponding infinite array is found. The presented method of coupling analysis can be considered as a supplement to the established periodic-structure approaches for infinite arrays and may be useful for the analysis of small or nonperiodic arrays.