Synthesis of near-field patterns of arrays
TL;DR: In this article, a new technique of synthesis of near-field amplitude and phase patterns of linear, planar, of volume arrays of finite size or arrays located on a planar contour of a finite size is presented.
Abstract: A new technique of synthesis of near-field (NF) amplitude and phase patterns of linear, planar, of volume arrays of finite size or arrays located on a planar contour of finite size is presented The array could consist of point dipoles or directive elements The criterion for prescribing the NF (amplitude and phase) pattern information in the synthesis problem for unique determination of array excitation currents is also stated The proposed near-field synthesis technique is based on the potential integral solution of source currents, Nyquist sampling of the near-field data and the technique of linear least square approximation (LLSA) The NF pattern synthesis technique is illustrated to synthesize a variety of NF patterns with a number of array configurations Application of the proposed NF pattern synthesis technique to minimize distortion in far-field patterns of arrays mounted on a conducting platform and to realize array antennas with low sidelobes in the near and far field is also presented
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TL;DR: In this paper, the basic working principles and applications of the NF-focused (NFF) microwave antennas as well as the synthesis procedures suggested for the NF shaping around the focal point and the technologies currently used for their implementation are discussed.
Abstract: Focusing the electromagnetic field radiated by an antenna at a point in the antenna near-field (NF) region is a wellknown technique to increase the electromagnetic power density in a size-limited spot region close to the antenna aperture. This article encompasses the basic working principles and the applications of the NF-focused (NFF) microwave antennas as well as the synthesis procedures suggested for the NF shaping around the focal point and the technologies currently used for their implementation.
128Â citations
TL;DR: In this paper, the authors present an efficient procedure for the synthesis of planar array antennas to radiate contoured patterns in the near zone of array aperture, as desired in RFID applications.
Abstract: We present an efficient procedure for the synthesis of planar array antennas to radiate contoured patterns in the near zone of array aperture, as desired in RFID applications. It first grids the target area, and then utilizes a global basis set to span the array's excitations. Each basis's excitation of the array radiates a focused spot beam in the near zone and serves as a local basis function for representing the radiation field. The unknown coefficients of the array's basis set are then found via a minimum least square error (MLSE) technique. It is found that only a small number of basis functions are sufficient to synthesize the radiation pattern, and make the present approach very fast.
40Â citations
Cites methods from "Synthesis of near-field patterns of..."
...Also [23], [24] further utilize potential integral solution of source currents, Nyquist sampling of near-field data, and LLSA to synthesize near-field patterns for several array configurations....
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TL;DR: In this paper, a microstrip planar array antenna is presented, which is designed to have near-field focused beams, and it is capable of steering its focus on the designed focal plane.
Abstract: A microstrip planar array antenna is presented in this paper, which is designed to have near-field focused beams, and it is capable of steering its focus on the designed focal plane. The array is composed of eight series-fed linear arrays, which are able to scan the focus by frequency around 10 GHz in the H-plane, whereas, E-plane focus scan can be achieved by feeding the linear arrays with different phases. The proposed array can be used in near-field scan systems, e.g., microwave imaging system, with a faster scan rate than mechanically scanned antennas and a lower cost than array antennas with full phase control elements. Theoretical analysis is presented in this paper, and is verified by simulations and experiments.
40Â citations
TL;DR: In this paper, a subwavelength array of planar monopoles is proposed, where each element of the array is etched aperiodically with many microstructured complementary split rings, and the proposed array can perform time-reversal far-field focusing with a spatial superresolution as small as one twentieth of a wavelength.
Abstract: With the aid of specific microstructures in a subwavelength array, time-reversed electromagnetic wave can display spatial super-resolution focusing in far-field zone. A subwavelength array of planar monopoles is proposed in this paper. Each element of the array, the planar monopole, is etched aperiodically with many microstructured complementary split rings. An important property of this antenna is that if multiple such planar monopoles are placed face to face, the proposed array can perform time-reversal far-field focusing with a spatial super-resolution as small as one twentieth of a wavelength. The validity of the proposed array with super-resolution characteristics is verified by the communication experiments with a data rate of 660 Mbit/s. The proposed subwavelength array is easy-to-design and convenient for integration.
34Â citations
TL;DR: In this article, a microstrip patch array antenna with a steepest descent method (SDM) was proposed to synthesize the excitation phases of the array such that the radiation has an optimum near-field pattern in the desired area.
Abstract: We present the design and realization of a microstrip patch array antenna, which is operated at 24 GHz band, and can be used in the applications of vital-sign detection with a higher resolution. The design uses the steepest descent method (SDM) to synthesize the excitation phases of the array such that the radiation has an optimum near-field pattern in the desired area. Both theoretical development of SDM formulations and experimental validations over the antenna prototype are presented.
28Â citations
Cites background or methods from "Synthesis of near-field patterns of..."
...In contrast to previous works [10], [11] focusing on investigating sophisticated theories of array synthesis, this paper presents relatively simple models and synthesis procedure based on steepest descent method (SDM) [8], and further realize a design of microstrip array antenna operated at 24 GHz band for the potential applications of vital-sign detection with a higher resolution....
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...This technique had been proved to be very effective in the applications of far-field satellite communications [8], [9], and can be similarly adopted in the current applications [10], [11]....
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References
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TL;DR: This paper considers stable numerical methods for handling linear least squares problems that frequently involve large quantities of data, and they are ill-conditioned by their very nature.
Abstract: A common problem in a Computer Laboratory is that of finding linear least squares solutions. These problems arise in a variety of areas and in a variety of contexts. Linear least squares problems are particularly difficult to solve because they frequently involve large quantities of data, and they are ill-conditioned by their very nature. In this paper, we shall consider stable numerical methods for handling these problems. Our basic tool is a matrix decomposition based on orthogonal Householder transformations.
764Â citations
TL;DR: Mathematical and numerical least squares solution of linear equations, using Householder algorithm as mentioned in this paper, using Household algorithm for least square solutions of linear equation, using least square solution.
Abstract: Mathematical and numerical least squares solution of linear equations, using Householder algorithm
142Â citations
TL;DR: In this article, a numerically stable algorithm for solving linear least-squares problems with linear equalities and inequalities as additional constraints is presented, which is related to Rosen's gradient projection method.
Abstract: This article presents a numerically stable algorithm for solving linear least-squares problems with linear equalities and inequalities as additional constraints. The method proposed is a method of feasible directions and is related to Rosen’s gradient projection method. Moreover, together with a discussion of possible extensions a simplified version of the basic algorithm for solving linear programming problems is described.
88Â citations
TL;DR: An exact analysis for deriving closed-form expressions for the coefficients of free-space spherical modes radiated by typical linear, array, and aperture type of antennas is presented in this article.
Abstract: An exact analysis for deriving closed-form expressions for the coefficients of free-space spherical modes radiated by typical linear, array, and aperture type of antennas is presented. This analysis is employed to determine the number of spherical modes required to reconstruct the near/ far fields (NF/FF) with a prescribed accuracy. The analysis developed together with the theory of probe-compensated spherical scanning is also employed to arrive at a criterion for the minimum distance of separation between the probe and test antenna which will enable accurate nonprobe corrected spherical scanning possible.
15Â citations
TL;DR: In this paper, a unified approach for synthesizing the near or far-field radiation patterns of an array of uniformly or non-uniformly spaced point sources or directive elements located on a planar contour of arbitrary shape is presented.
Abstract: A unified approach for synthesizing the near- or far-field radiation patterns of an array of uniformly or nonuniformly spaced point sources or directive elements located on a planar contour of arbitrary shape is presented. The synthesis problem is formulated employing the free-space Green's dyadic as well as the translational and rotational addition theorems for spherical vector wave functions. A similar unified approach for synthesizing the near- or far-field radiation patterns of a uniformly or nonuniformly spaced linear array of point dipoles is also presented. The validity of the technique presented is established with several typical numerical illustrations.
7Â citations