Two-dimensional beam steering using an electrically tunable impedance surface
TL;DR: In this article, a periodic surface texture is used to alter the electromagnetic properties of a metal ground plane by covering the surface with varactor diodes, and a tunable impedance surface is built, in which an applied bias voltage controls the resonance frequency and the reflection phase.
Abstract: By covering a metal ground plane with a periodic surface texture, we can alter its electromagnetic properties. The impedance of this metasurface can be modeled as a parallel resonant circuit, with sheet inductance L, and sheet capacitance C. The reflection phase varies with frequency from +/spl pi/ to -/spl pi/, and crosses through 0 at the LC resonance frequency, where the surface behaves as an artificial magnetic conductor. By incorporating varactor diodes into the texture, we have built a tunable impedance surface, in which an applied bias voltage controls the resonance frequency, and the reflection phase. We can program the surface to create a tunable phase gradient, which can electronically steer a reflected beam over +/- 40/spl deg/ in two dimensions, for both polarizations. We have also found that this type of resonant surface texture can provide greater bandwidth than conventional reflectarray structures. This new electronically steerable reflector offers a low-cost alternative to a conventional phased array.
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TL;DR: In this article, the basic physics and applications of planar metamaterials, often called metasurfaces, which are composed of optically thin and densely packed planar arrays of resonant or nearly resonant subwavelength elements, are reviewed.
1,047 citations
TL;DR: In this paper, simple analytical formulas are introduced for the grid impedance of electrically dense arrays of square patches and for the surface impedance of high-impedance surfaces based on the dense array of metal strips or square patches over ground planes.
Abstract: Simple analytical formulas are introduced for the grid impedance of electrically dense arrays of square patches and for the surface impedance of high-impedance surfaces based on the dense arrays of metal strips or square patches over ground planes. Emphasis is on the oblique-incidence excitation. The approach is based on the known analytical models for strip grids combined with the approximate Babinet principle for planar grids located at a dielectric interface. Analytical expressions for the surface impedance and reflection coefficient resulting from our analysis are thoroughly verified by full-wave simulations and compared with available data in open literature for particular cases. The results can be used in the design of various antennas and microwave or millimeter wave devices which use artificial impedance surfaces and artificial magnetic conductors (reflect-array antennas, tunable phase shifters, etc.), as well as for the derivation of accurate higher-order impedance boundary conditions for artificial (high-) impedance surfaces. As an example, the propagation properties of surface waves along the high-impedance surfaces are studied.
636 citations
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24 Nov 2008TL;DR: In this paper, the FDTD method for periodic structure analysis is used for periodic structures analysis of EBG surfaces and low profile wire antennas are used for EBG surface wave antennas.
Abstract: Preface 1. Introduction 2. FDTD Method for periodic structure analysis 3. EBG Characterizations and classifications 4. Design and optimizations of EBG structures 5. Patch antennas with EBG structures 6. Low profile wire antennas on EBG surfaces 7. Surface wave antennas Appendix: EBG literature review.
634 citations
TL;DR: In this article, the authors introduce several different design methodologies for multiband artificial magnetic conducting (AMC) surfaces, based on the introduction of FSS screens that have fractal or nearly fractal unit cell geometries.
Abstract: This paper introduces several different design methodologies for multiband artificial magnetic conducting (AMC) surfaces. The paper begins by investigating the multiband properties exhibited by a conventional electromagnetic bandgap (EBG) AMC that consists of a frequency selective surface (FSS) on top of a thin dielectric substrate with a PEC back plane. The higher-order resonances associated with these surfaces have not been discussed in detail to date, as previous research has been concerned only with exploiting the primary resonant frequency. However, it will be shown that by understanding and making appropriate use of these higher order resonances, it is possible to design multiband AMC surfaces that work for nearly any desired combination of operating frequencies. The first multiband AMC design approach that will be considered is based on the introduction of FSS screens that have fractal or nearly fractal unit cell geometries. This is followed by a more general and robust genetic algorithm (GA) technique for the synthesis of optimal multiband AMC surfaces. In this case, a GA is used to evolve multiband AMC surface designs by simultaneously optimizing the geometry and size of the FSS unit cell as well as the thickness and dielectric constant of the substrate material. Finally, several examples of multiband AMC surfaces are presented, including some practical dual-band and tri-band designs genetically evolved for operation at GPS and cellular frequencies, as well as an example illustrating the success in creating a multiband AMC surface with angular stability.
384 citations
Cites methods from "Two-dimensional beam steering using..."
...By periodically loading an EBG structure with these tunable capacitors, it is possible to utilize the EBG surface to steer a reflected beam and provide greater bandwidth than conventional reflectarray structures [23]....
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TL;DR: In this paper, the progress in some materials and structures for electromagnetic applications, such as microwave absorption, electric shielding and antenna designs, which have been developed in recent years are summarized.
Abstract: This review aims to summarise the progress in some materials and structures for electromagnetic applications, such as microwave absorption, electric shielding and antenna designs, which have been developed in recent years. Composites with spherical powders for microwave absorption focus mainly on those based on ferrites (especially hexagonal), carbonyl iron and related alloys and various newly emerged nanosized materials. Composites with long conductive fibres as fillers will be summarised, with speical attentions to prediction, measurment and evaluation of their performances. Metamaterials include structures for microwave absorbing applications, tunable materials or structures with reflection or transmission coefficients that are tunable by external magnetic or electric fields, and specially designed structures for microwave absorbing applications, with thickness much smaller than that of conventional composite materials and performances that can be optimised by the physical properties of substra...
378 citations
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TL;DR: In this paper, a new type of metallic structure has been developed that is characterized by having high surface impedance, which is analogous to a corrugated metal surface in which the corrugations have been folded up into lumped-circuit elements and distributed in a two-dimensional lattice.
Abstract: A new type of metallic electromagnetic structure has been developed that is characterized by having high surface impedance. Although it is made of continuous metal, and conducts dc currents, it does not conduct ac currents within a forbidden frequency band. Unlike normal conductors, this new surface does not support propagating surface waves, and its image currents are not phase reversed. The geometry is analogous to a corrugated metal surface in which the corrugations have been folded up into lumped-circuit elements, and distributed in a two-dimensional lattice. The surface can be described using solid-state band theory concepts, even though the periodicity is much less than the free-space wavelength. This unique material is applicable to a variety of electromagnetic problems, including new kinds of low-profile antennas.
4,264 citations
"Two-dimensional beam steering using..." refers background in this paper
...The surface wave properties of these materials are described in greater detail elsewhere [9], [10]....
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...The reduction in thickness is achieved by capacitive loading, such as by using closely spaced mushroom-shaped metal protrusions, or overlapping thumbtack-like structures [9], [10]....
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TL;DR: In this paper, the physical limitations of omni-directional antennas are considered and the potentiality of a broad band width of an antenna with the maximum dimension of 2a has been shown.
Abstract: The physical limitations of omni‐directional antennas are considered. With the use of the spherical wave functions to describe the field, the directivity gain G and the Q of an unspecified antenna are calculated under idealized conditions. To obtain the optimum performance, three criteria are used, (1) maximum gain for a given complexity of the antenna structure, (2) minimum Q, (3) maximum ratio of G/Q. It is found that an antenna of which the maximum dimension is 2a has the potentiality of a broad band width provided that the gain is equal to or less than 4a/λ. To obtain a gain higher than this value, the Q of the antenna increases at an astronomical rate. The antenna which has potentially the broadest band width of all omni‐directional antennas is one which has a radiation pattern corresponding to that of an infinitesimally small dipole.
1,954 citations
01 Dec 1947
TL;DR: In this paper, a simple formula for the more fundamental properties of small antennas and their behavior in a simple circuit is given for 1-Mc operation in typical circuits, which indicates a loss of about 35 db for the I.R.E. standard capacitive antenna, 43 db for a large loop occupying a volume of 1 meter square by 0.5 meter axial length, and 64 db for an antenna loop of 1/5 these dimensions.
Abstract: A capacitor or inductor operating as a small antenna is theoretically capable of intercepting a certain amount of power, independent of its size, on the assumption of tuning without circuit loss. The practical efficiency relative to this ideal is limited by the "radiation power factor" of the antenna as compared with the power factor and bandwidth of the antenna tuning. The radiation power factor of either kind of antenna is somewhat greater than (1/6π) (Ab/l2) in which Ab is the cylindrical volume occupied by the antenna, and l is the radianlength (defined as 1/2π wavelength) at the operating frequency. The efficiency is further limited by the closeness of coupling of the antenna with its tuner. Other simple formulas are given for the more fundamental properties of small antennas and their behavior in a simple circuit. Examples for 1-Mc. operation in typical circuits indicate a loss of about 35 db for the I.R.E. standard capacitive antenna, 43 db for a large loop occupying a volume of 1 meter square by 0.5 meter axial length, and 64 db for a loop of 1/5 these dimensions.
1,249 citations
"Two-dimensional beam steering using..." refers background in this paper
...[25] L. Chu, “Physical limitations of Omni-directional antennas,”J. Appl....
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...We recognize as the radian length in (7) [24]....
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...The field distribution within a resonant textured surface affects its bandwidth in much the same way as for a small resonant antenna, as first described by Wheeler and Chu [24]–[26]....
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TL;DR: In this paper, the theoretical modeling and practical design of millimeter wave reflectarrays using microstrip patch elements of variable size is discussed and a full-wave treatment of plane wave reflection from a uniform infinite array of microstrip patches is described and used to generate the required patch-design data and to calculate the radiation patterns of the reflectarray.
Abstract: This paper discusses the theoretical modeling and practical design of millimeter wave reflectarrays using microstrip patch elements of variable size. A full-wave treatment of plane wave reflection from a uniform infinite array of microstrip patches is described and used to generate the required patch-design data and to calculate the radiation patterns of the reflectarray. The critical parameters of millimeter wave reflectarray design, such as aperture efficiency, phase errors, losses, and bandwidth are also discussed. Several reflectarray feeding techniques are described, and measurements from four reflectarray design examples at 28 and 77 GHz are presented.
1,142 citations
"Two-dimensional beam steering using..." refers background in this paper
...It is known that the geometry of the resonant elements can have a significant effect on the performance of reflectarrays [16], [17], so we examined the effect of the plate geometry on the properties of our textured surface....
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...Indeed, similar trends in bandwidth are seen for traditional reflectarrays [16], [17]....
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TL;DR: In this paper, an exact method for the calculation of the minimum radiation Q of a general antenna was derived, which is more straightforward than those previously published, and has implications on both the bandwidth and efficiency of antennas which fall into this category.
Abstract: An exact method, which is more straightforward than those previously published, is derived for the calculation of the minimum radiation Q of a general antenna. This expression agrees with the previously published and widely cited approximate expression in the extreme lower limit of electrical size. However, for the upper end of the range of electrical size which is considered electrically small, the exact expression given here is significantly different from the approximate expression. This result has implications on both the bandwidth and efficiency limitations of antennas which fall into this category.
978 citations