Search

Angle of arrival (AoA) for target echo signal detection is crucial in vehicular radar systems, where the estimation of signal parameters via rotational invariance (ESPRIT) provides a high-resolution estimation. A subarray decomposition strategy is presented in this article to create two ESPRIT antenna arrays with enhanced echo signal strengths, applicable to multi-input–multioutput (MIMO) operations for creating a large virtual array. The concept intends to maximize the echo signal’s strength with minimum signal interferences by increasing the aperture sizes of the two ESPRIT antenna arrays. The decomposition produces two virtually overlapped subarrays to increase the subarray aperture sizes in the spatial or spectral representations. It is applied to the MIMO-based arrays for two-way radiation patterns for ESPRIT estimation of AoA. Numerical simulation examples are shown to validate the feasibility and demonstrate the applications. [ABSTRACT FROM AUTHOR]

This study proposes an improved method for sector nulling in the radiation pattern of rectangular phased array antennas using two different synthesis techniques; an orthogonal Discrete Fourier transform and a quasi‐orthogonal Dolph‐Tschebyscheff based technique. In traditional synthesis techniques, broad elemental beams serve as local field basis functions (FBFs) in an array. Instead, the proposed methods produce low sidelobe narrow beams as FBFs. A set of these FBFs can effectively constitute the array's radiation pattern in a confined angular region. By properly weighting these FBFs, sector pattern nulls in a designated angular range are synthesized without severely distorting the patterns outside this area. The FBFs' optimal weights can be efficiently calculated using a nonlinear minimum least squares error technique, which is later transformed into the array's elemental excitation coefficients. Along with faster convergence, this technique allows control over peak sidelobe level, null depth, and width, making it suitable for GPS anti‐jamming, 5G communications, and other applications requiring interference suppression. Key Points: Two localized beam cancellation methods for antenna pattern nulling are proposedThe theoretical formulations of a Discrete Fourier Transform and a Dolph‐Tschebyscheff based algorithm are explainedNumerical examples demonstrating the effectiveness of the algorithms are presented [ABSTRACT FROM AUTHOR]

A dual-band circularly polarized horn antenna of completely inhomogeneous corrugations is efficiently designed for simultaneous good polarization, aperture efficiency (AE), sidelobe level (SLL), and symmetric radiation pattern (SRP). The method employs two steps to integrate a mode-matching method and a genetic algorithm by introducing a modal expansion of the aperture field as an intermediate interface for optimization, where the selected modes’ weightings are first optimized to resemble the desirable far-field patterns. Afterward, the aperture distribution serves as the goal to subsequently optimize the entire corrugation structure by formatting related scattering matrices using the weighting coefficients of available modes on the aperture and inside the horn section. In the implementation of design, the developed corrugated horn comprises six and 19 completely inhomogeneous corrugations in mode conversion and radiation sections, respectively, providing sufficient design freedom. Simulated and measured results are shown to validate the optimized horn design, which simultaneously meets all above-mentioned requirements in both the K-band (19.6–21.2 GHz) and the Ka-band (29.4–31 GHz). [ABSTRACT FROM AUTHOR]

This paper presents the design of 2-D phased array of antennas to radiate collinear multiple beams properly distributed for near-field (NF) focus (NFF) applications. In the design, the 2-D array is first decomposed into single-column subarrays, where each of the subarrays is identically excited to radiate a vertically NFF beam with the focal points located at a designated distance along the boresight direction of each subarray aperture. Afterward, the NFF column subarrays become the elements of a 1-D horizontal collinearly located array to radiate horizontally NFF multiple beams. The horizontal NFF beamforming network is implemented by extending the basic concept of conventional Rotman lens beamformer for directional NFF multibeam applications. Thus, three feeding points are selected to determine the lens’s profile such that the produced phases via the modified Rotman lens can be used to feed a planar array to radiate three NFF beams when the lens is excited at the three selected points, respectively. This antenna set is realized at 2.45 GHz for radio frequency identification applications to demonstrate the implementation concept. Both the simulation and experimental measurement results are shown to validate the feasibility. [ABSTRACT FROM AUTHOR]

This letter presents a practical measurement scheme to characterize the radiation of electrically large phased arrays of antennas with high-power excitations. In particular, the proposed scheme is applicable to conduct the measurement in an ordinary anechoic chamber with limited power supply to simulate the radiation scenario of realistic high-power phased array antennas. This scheme first decomposes the original large array into virtually overlapped subarrays whose radiation patterns are used to compose the original radiation pattern. In addition, the subarrays’ radiation patterns may serve as field basis functions to synthesize a desired pattern anticipated in the original phased array of antennas for radiation calibration. [ABSTRACT FROM AUTHOR]

This communication presents a shaped reflector antenna for radiating five quasi-orthogonal beams for radio coverage of mobile communication at 38 GHz. The feeds are miniaturized by replacing the horn section of the waveguide with a lens structure to avoid an over-crowded accommodation. This configuration has the advantages of subdividing the coverage area and radiating dual-polarized fields to enhance the communication capacity by using a single set of antennas. The overlapped pattern spans an angular coverage of 51° with an efficiency of 88%, which is particularly suitable for mobile cell networks. The numerical and measurement results in terms of radiation patterns and the subsequent results of network modeling are discussed to demonstrate the characteristics of radiation and beam orthogonality. [ABSTRACT FROM AUTHOR]

This article presents an investigation into the radiation characteristics of broadband, all-metallic reflectarray antennas with nonresonant convex elements for directional beam applications. The metallic reflecting elements demonstrate advantages over conventional elements that are realized on printed circuit board (PCB)-type dielectric substrates because of the superiority in energy efficiency of these metal elements. The use of the metallic elements results in more radiation power to compensate for the energy loss that occurs during propagation in air. These radiation characteristics cause the antennas to radiate a broader beam with a smaller physical size and with the same gain achievement as that of a PCB-based antenna, resulting in better coverage. [ABSTRACT FROM AUTHOR]

In this paper, we present the design of metallic reflectarray antennas consisting of convex nonresonant elements to radiate multiple beams with optimum radiation gains and relatively orthogonal overlapping. In particular, an antenna is realized at 38 GHz to provide sufficient gains and beam widths for simultaneous link-budget and radio coverage satisfaction in the applications of fifth-generation mobile communications. The pattern optimization employs the steepest decent method (SDM) to optimize the phases of reflecting elements for gain tradeoff. The SDM procedure is very efficient because relatively simple formulations of analysis in closed form are developed to subsequently update the phases in each iteration. This procedure avoids the cumbersome and numerous full-wave numerical simulations of scattering fields. Design examples and their radiation characteristics are presented to demonstrate the concepts and validate the feasibility. [ABSTRACT FROM AUTHOR]

This communication examines how to improve the squinted radiation patterns produced by the balanced antipodal Vivaldi antenna (BAVA) while retaining its cross-polarization levels. In particular, we propose discarding the redundant substrate between the metal flares of the BAVA and implementing dual-scale slotted edges to improve the radiation characteristics. The gain at both the lower and the higher end of the band is significantly enhanced without increasing the antenna size. Moreover, significant reduction in the beam squint relative to the conventional BAVA designs is achieved. A microstrip-to-stripline transition is also introduced to improve low-end matching. The final design operates over 10–40 GHz with return loss <−10 dB, providing sufficient bandwidth and match for a variety of applications at millimeter-wave frequencies. Numerical and experimental assessments to validate the proposed antenna design are conducted. [ABSTRACT FROM AUTHOR]

The radiation characteristics of reflector antenna are investigated when its aperture field is grated by using a nonperiodic Fresnel-zone plate lens (FZPL). The focus of study intends to develop a theoretic foundation such that the radiating slot rings can be adjusted to reduce the sidelobes. In particular, the results of slot ring radiation may reduce to the radiation of a 1-D unequally spaced radiating sources. This reduction allows one to employ the conventional array theories of unequally spaced elements to determine the configuration of FZPL. Theoretic formulation as well as demonstrating examples is presented to validate the concept. [ABSTRACT FROM PUBLISHER]

A multilevel subarray RF modularization technique is presented to construct a hierarchical beamforming network (BFN) for phased array of antennas. In contrast to the conventional BFN architecture, which feeds each antenna element by using individual set of RF devices, the restructured RF modules may simplify the BFN architecture. They may dramatically reduce the cost without significantly sacrificing the radiation performance. In this technique, the RF devices to feed antenna elements are subdivided into groups for modularization. Each module is formed by very few elements of RF devices to form a multilevel BFN, where the number of RF elements in each module are the integer factors of array size. Each module at the same layer consists of identical RF structures to minimize the mass manufacture cost. In this paper, the theoretical foundation is developed to provide design guidelines. Examination of radiation discrepancy is also investigated to demonstrate the feasibility and validate the proposed technique. [ABSTRACT FROM AUTHOR]

This communication presents the design of a dual-band hybrid antenna for digital television (DTV) and wireless local area network (WLAN) applications. Radiations are produced with spatial diversity for WLAN applications to realize multiple-input–multiple-output functionality and omnidirectional coverage. The structure embeds two slots into an ultrawideband monopole body for high- and low-frequency operations, which are excited by three ports of DTV and WLAN. The resultant frequency bandwidth covers most of the global DTV frequencies and the free WLAN band at 2.45 GHz. The radiations exhibit omnidirectional patterns for all three cases. Numerical and measurement results are presented to demonstrate the characteristics of radiation. [ABSTRACT FROM AUTHOR]

This paper presents an effective optimization procedure to calibrate the deviations of beam patterns radiated from phased arrays of antennas. The pattern distortions occur from the discretization of the radio-frequency (RF) components’ output and the residue errors in amplitudes and phases from manufacturing discrepancies. This technique implements a genetic algorithm (GA) with an antenna measurement facility, and allows one to optimize the radiation patterns by using the actual phase and amplitude states of the RF components. The optimization variables are the control codes of the RF components, which are more direct and applicable to the GA as binary codes, rather than the phases and amplitudes of the elemental excitations. The systematic procedure and demonstration examples are presented to validate the feasibility. [ABSTRACT FROM PUBLISHER]

This paper presents the design methodology of phased array antennas to radiate multiple beams, where each beam is equipped with an I/O port to allow independent uses. The potential applications include multicoverages in the mobile communications and multisatellite signal receptions using a single set of antennas. In particular, the beam-forming circuits employ Butler matrix (BM) as the core. Both the beam-forming mechanisms and the implementation of BM are presented. The uniqueness of this paper is that the coverage domain can be relatively arbitrarily defined, within which the beams will uniformly distributed. The beamwidth can be further flexibly controlled to provide an appropriate beam overlapping, which is important for the isolation of coverages. Numerical examples are presented to investigate the characteristics of this method and also demonstrate the feasibility. [ABSTRACT FROM PUBLISHER]

This communication presents a calibration technique to suppress multipath signals by using the measured data of a single frequency in a hybrid antenna measurement chamber. The technique employs the matrix pencil method to diagnose the multipath characteristics, and results in a calibration factor by using a reference antenna. The radiation pattern of the antenna under test (AUT) is then recovered from the measurement by incorporating this calibration factor without the need to perform multiple measurements over the AUT. Examples are presented to demonstrate the feasibility and utilization of this technique. [ABSTRACT FROM AUTHOR]

A time-domain (TD) analysis of ellipsoidal reflector antennas is presented to predict the transient scattered fields when it is illuminated by a cosine-tapered and transient-step feed radiation whose phase center is located at the nearby focus. A transient-step function of the feed's radiation is considered because it will produce an impulsive response near the second focus of the reflector as interested in the applications of impulse-radiating antennas. This TD solution is in a closed form and remains valid both near and far from the reflector, and can be used via the convolution theorem to efficiently obtain the early time transient fields generated by the same ellipsoidal reflector antenna when it is illuminated by a realistic finite-energy pulse which emanates as a spherical wave from the focus. Numerical results are presented for the transient fields both near and far from the reflector. [ABSTRACT FROM PUBLISHER]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A broadband antenna designed to radiate high directive circularly polarized radiations is presented. This design utilizes spiral arms to achieve a broad frequency bandwidth and radiates circularly polarized fields. To enhance the directivity, the spiral arms are axially elevated to have a radiation beamwidth narrower than that radiated from an analogous spiral antenna in the upward direction. This antenna is suitable for many microwave applications. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 303–305, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24040 [ABSTRACT FROM AUTHOR]