Wideband Near-Field Correction of a Fabry–Perot Resonator Antenna
07 Jan 2019-IEEE Transactions on Antennas and Propagation (Institute of Electrical and Electronics Engineers (IEEE))-Vol. 67, Iss: 3, pp 1975-1980
TL;DR: In this paper, an approach to correcting electric near-field phase and magnitude over a wideband for Fabry-Perot resonator antennas (FPRAs) is presented, where a time-average Poynting vector in conjunction with a phase gradient analysis is utilized to suggest the initial configuration of the NFCS for wideband performance.
Abstract: A systematic approach to correcting electric near-field phase and magnitude over a wideband for Fabry–Perot resonator antennas (FPRAs) is presented. Unlike all other unit-cell-based near-field correction techniques for FPRAs, which merely focus on phase correction at a single frequency, this method delivers a compact near-field correcting structure (NFCS) with a wide operational bandwidth of 40%. In this novel approach, a time-average Poynting vector in conjunction with a phase gradient analysis is utilized to suggest the initial configuration of the NFCS for wideband performance. A simulation-driven optimization algorithm is then implemented to find the thickness of each correcting region, defined by the gradient analysis, to complete the NFCS design. According to the predicted and measured results, the phase and magnitude distributions of the electric near field have been greatly improved, resulting in a high aperture efficiency of 70%. The antenna under NFCS loading has a peak measured directivity of 21.6 dB, a 3 dB directivity bandwidth of 41% and a 10 dB return loss bandwidth of 46%, which covers the directivity bandwidth. The diameter of the proposed NFCS is $3.8\lambda _{0c}$ , which is around half that of all the other unit-cell-based phase-correcting structures, where $\lambda _{0c}$ is the free-space wavelength at the central frequency of the NFCS (13.09 GHz).
Citations
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TL;DR: In this paper, a hybrid topology of fully metallic spatial phase shifters is developed for the AMPCS, resulting in an extremely lower prototyping cost as that of other state-of-the-art substrate-based PCSs.
Abstract: This article addresses a critical issue, which has been overlooked, in relation to the design of phase-correcting structures (PCSs) for electromagnetic bandgap (EBG) resonator antennas (ERAs). All the previously proposed PCSs for ERAs are made using either several expensive radio frequency (RF) dielectric laminates or thick and heavy dielectric materials, contributing to very high fabrication cost, posing an industrial impediment to the application of ERAs. This article presents a new industrial-friendly generation of PCS, in which dielectrics, known as the main cause of high manufacturing cost, are removed from the PCS configuration, introducing an all-metallic PCS (AMPCS). Unlike existing PCSs, a hybrid topology of fully metallic spatial phase shifters are developed for the AMPCS, resulting in an extremely lower prototyping cost as that of other state-of-the-art substrate-based PCSs. The APMCS was fabricated using laser technology and tested with an ERA to verify its predicted performance. The results show that the phase uniformity of the ERA aperture has been remarkably improved, resulting in 8.4 dB improvement in the peak gain of the antenna and improved sidelobe levels (SLLs). The antenna system including APMCS has a peak gain of 19.42 dB with a 1 dB gain bandwidth of around 6%.
72 citations
Cites background from "Wideband Near-Field Correction of a..."
...manipulate the local aperture-phase values for phase-error minimization at the operating frequency [9]–[11]....
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66 citations
Cites methods from "Wideband Near-Field Correction of a..."
...Recently, CI methods have been used to model and simulate numerous types of dynamic systems, which can be varied from cognitive science, industrial robotics(2,3) to electromagnetics and microwave components.(4-13) Such evolutionary algorithms can be incorporated into the design procedure for either optimizing a suboptimal structure or realizing a nonintuitive configuration....
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TL;DR: An intelligent design methodology of microstrip filters in which a dynamic neural network model based on Bayesian Regularization Back-Propagation (BRBP) learning algorithm is used, suggesting an excellent in and out-of-band performance.
Abstract: This paper presents an intelligent design methodology of microstrip filters in which a dynamic neural network model based on Bayesian Regularization Back-Propagation (BRBP) learning algorithm is used. In this approach, a Low-Pass Filter (LPF) composed of multiple open stubs, and stepped impedance resonators is initially designed for which an Artificial Neural Network (ANN) is trained to improve the performance of the filter. The predicted and measured results of the filter verify the effectiveness of the presented method, suggesting an excellent in and out-of-band performance. According to the measurement, the filter has a very small transition band from 2.087 to 2.399 GHz with 3 and 40 dB attenuation points, respectively, leading to a sharp roll-off rate of 118.6 dB/GHz. In addition the optimized filter has an ultra-wide stopband, extending from 2.399 to 15.01 GHz with attenuation level of 22 dB are The overall size of the fabricated filter is only 0.190 λ g × 0.094 λ g , where λ g is the guided wavelength at 3 dB cut-off frequency (2.087 GHz). A performance comparison with some of the recent published LPFs presented, showing the superiority of the proposed filter.
56 citations
TL;DR: In this paper, the authors proposed a method to reduce the number of dominant grating lobes by optimizing a supercell using Floquet analysis and multi-objective particle swarm optimization.
Abstract: High-directivity antenna systems that provide 2-D beam steering by rotating a pair of phase-gradient metasurfaces (PGMs) in the near field of a fixed-beam antenna, hereafter referred to as near-field meta-steering systems, are efficient, planar, simple, short, require less power to operate, and do not require antenna tilting. However, when steering the beam, such systems generate undesirable dominant grating lobes, which substantially limit their applications. Optimizing a pair of these metasurfaces to minimize the grating lobes using standard methods is nearly impossible due to their large electrical size and thousands of small features leading to high computational costs. This article addresses this challenge as follows. First, it presents a method to efficiently reduce the strength of “offending” grating lobes by optimizing a supercell using Floquet analysis and multi-objective particle swarm optimization. Second, it investigates the effects of the transmission phase gradient of PGMs on radiation-pattern quality. It is shown that the number of dominant unwanted lobes in a 2-D beam-steering antenna system and their levels can be reduced substantially by increasing the transmission phase gradient of the two PGMs. This knowledge is then extended to 2-D beam-steering systems, where we demonstrate how to substantially reduce all grating lobes to a level below −20 dB for all beam directions, without applying any amplitude tapering to the aperture field. When steering the beam of two meta-steering systems with peak directivities of 30.5 and 31.4 dBi, within a conical volume with an apex angle of 96°, the variation in directivity is 2.4 and 3.2 dB, respectively. We also demonstrate that beam-steering systems with steeper gradient PGMs can steer the beam in a wider range of directions, require less mechanical rotation of metasurfaces to obtain a given scan range, and their beam steering is faster. The gap between the two metasurfaces in a near-field meta-steering system can be reduced to one-eighth of a wavelength with no significant effect on pattern quality.
50 citations
Cites background from "Wideband Near-Field Correction of a..."
...of resonant cavity antennas, a microstrip patch array or a metasurface antenna [33]–[36]....
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TL;DR: The AMPS has remarkably improved the radiation performance of ERA by increasing its far-field directivity from 12.67 dB to 21.12 dB and reducing side-lobe level from −7.3 dB to −17.2 dB.
Abstract: Additively manufactured perforated superstrate (AMPS) is presented to realize directive radio frequency (RF) front-end antennas. The superstrate comprises spatially distributed dielectric unit-cell elements with square perforations, which creates a pre-defined transmission phase delay pattern in the propagating electric field. The proposed square perforation has superior transmission phase characteristics compared to traditionally machined circular perforations and full-wave simulations based parametric analysis has been performed to highlight this supremacy. The AMPS is used with a classical electromagnetic-bandgap resonator antenna (ERA) to improve its directive radiation characteristics. A prototype is developed using the most common, low-cost and easily accessible Acrylonitrile Butadiene Styrene (ABS) filament. The prototype was rapidly fabricated in less than five hours and weighs 139.3 g., which corresponds to the material cost of only 2.1 USD. The AMPS has remarkably improved the radiation performance of ERA by increasing its far-field directivity from 12.67 dB to 21.12 dB and reducing side-lobe level from -7.3 dB to -17.2 dB.
38 citations
Cites background from "Wideband Near-Field Correction of a..."
...It is reported that a non-uniform aperture phase distribution in the electric near-field restricts the far-field directivity of classical ERAs despite having a large lateral size [36], [37]....
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TL;DR: In this paper, the authors investigated the effect of placing a partially reflecting sheet in front of an antenna with a reflecting screen at a wavelength of 3.2 cm and showed that large arrays produce considerably greater directivity but their efficiency is poor.
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977 citations
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