Showing papers in "IEEE Transactions on Antennas and Propagation in 2005"
TL;DR: An overview of antenna design for passive radio frequency identification (RFID) tags is presented, which outlines a generic design process including range measurement techniques and focuses on one practical application: RFID tag for box tracking in warehouses.
Abstract: In this paper, an overview of antenna design for passive radio frequency identification (RFID) tags is presented. We discuss various requirements of such designs, outline a generic design process including range measurement techniques and concentrate on one practical application: RFID tag for box tracking in warehouses. A loaded meander antenna design for this application is described and its various practical aspects such as sensitivity to fabrication process and box content are analyzed. Modeling and simulation results are also presented which are in good agreement with measurement data.
1,268 citations
TL;DR: In this article, a planar circular disc monopole has been demonstrated to provide an ultra wide 10 dB return loss bandwidth with satisfactory radiation properties, and the parameters which affect the performance of the antenna in terms of its frequency domain characteristics are investigated.
Abstract: This paper presents a study of a novel monopole antenna for ultrawide-band (UWB) applications. Printed on a dielectric substrate and fed by a 50 /spl Omega/ microstrip line, a planar circular disc monopole has been demonstrated to provide an ultra wide 10 dB return loss bandwidth with satisfactory radiation properties. The parameters which affect the performance of the antenna in terms of its frequency domain characteristics are investigated. A good agreement is achieved between the simulation and the experiment. In addition, the time domain performance of the proposed antenna is also evaluated in simulations.
948 citations
TL;DR: In this article, a ray analysis is employed in order to give physical insight into the performance of AMCs and derive design guidelines, and the bandwidth and center frequency of AMC surfaces are investigated using full-wave analysis and the qualitative predictions of the ray model are validated.
Abstract: Planar periodic metallic arrays behave as artificial magnetic conductor (AMC) surfaces when placed on a grounded dielectric substrate and they introduce a zero degrees reflection phase shift to incident waves. In this paper the AMC operation of single-layer arrays without vias is studied using a resonant cavity model and a new application to high-gain printed antennas is presented. A ray analysis is employed in order to give physical insight into the performance of AMCs and derive design guidelines. The bandwidth and center frequency of AMC surfaces are investigated using full-wave analysis and the qualitative predictions of the ray model are validated. Planar AMC surfaces are used for the first time as the ground plane in a high-gain microstrip patch antenna with a partially reflective surface as superstrate. A significant reduction of the antenna profile is achieved. A ray theory approach is employed in order to describe the functioning of the antenna and to predict the existence of quarter wavelength resonant cavities.
907 citations
TL;DR: In this article, exact and approximate expressions for the bandwidth and Q of a general single-feed (one-port) lossy or lossless linear antenna tuned to resonance or antiresonance were derived.
Abstract: To address the need for fundamental universally valid definitions of exact bandwidth and quality factor (Q) of tuned antennas, as well as the need for efficient accurate approximate formulas for computing this bandwidth and Q, exact and approximate expressions are found for the bandwidth and Q of a general single-feed (one-port) lossy or lossless linear antenna tuned to resonance or antiresonance. The approximate expression derived for the exact bandwidth of a tuned antenna differs from previous approximate expressions in that it is inversely proportional to the magnitude |Z'/sub 0/(/spl omega//sub 0/)| of the frequency derivative of the input impedance and, for not too large a bandwidth, it is nearly equal to the exact bandwidth of the tuned antenna at every frequency /spl omega//sub 0/, that is, throughout antiresonant as well as resonant frequency bands. It is also shown that an appropriately defined exact Q of a tuned lossy or lossless antenna is approximately proportional to |Z'/sub 0/(/spl omega//sub 0/)| and thus this Q is approximately inversely proportional to the bandwidth (for not too large a bandwidth) of a simply tuned antenna at all frequencies. The exact Q of a tuned antenna is defined in terms of average internal energies that emerge naturally from Maxwell's equations applied to the tuned antenna. These internal energies, which are similar but not identical to previously defined quality-factor energies, and the associated Q are proven to increase without bound as the size of an antenna is decreased. Numerical solutions to thin straight-wire and wire-loop lossy and lossless antennas, as well as to a Yagi antenna and a straight-wire antenna embedded in a lossy dispersive dielectric, confirm the accuracy of the approximate expressions and the inverse relationship between the defined bandwidth and the defined Q over frequency ranges that cover several resonant and antiresonant frequency bands.
831 citations
TL;DR: This paper describes the synthesis method of linear array geometry with minimum sidelobe level and null control using the particle swarm optimization (PSO) algorithm, a newly discovered, high-performance evolutionary algorithm capable of solving general N-dimensional, linear and nonlinear optimization problems.
Abstract: This paper describes the synthesis method of linear array geometry with minimum sidelobe level and null control using the particle swarm optimization (PSO) algorithm. The PSO algorithm is a newly discovered, high-performance evolutionary algorithm capable of solving general N-dimensional, linear and nonlinear optimization problems. Compared to other evolutionary methods such as genetic algorithms and simulated annealing, the PSO algorithm is much easier to understand and implement and requires the least of mathematical preprocessing. The array geometry synthesis is first formulated as an optimization problem with the goal of sidelobe level (SLL) suppression and/or null placement in certain directions, and then solved by the PSO algorithm for the optimum element locations. Three design examples are presented that illustrate the use of the PSO algorithm, and the optimization goal in each example is easily achieved. The results of the PSO algorithm are validated by comparing with results obtained using the quadratic programming method (QPM).
634 citations
TL;DR: In this article, the fundamental properties of dipole transmitting antennas formed by carbon nanotubes are investigated, and the input impedance, current profile, and efficiency are presented, as well as possible applications.
Abstract: Fundamental properties of dipole transmitting antennas formed by carbon nanotubes are investigated. Since carbon nanotubes can be grown to centimeter lengths, and since they can be metallic, the properties of carbon nanotubes as antenna elements are of fundamental interest. In this paper, dipole carbon nanotube antennas are investigated via a classical Hallen's-type integral equation, based on a quantum mechanical conductivity. The input impedance, current profile, and efficiency are presented, and the radiation pattern is discussed, as are possible applications.
432 citations
TL;DR: In this article, a single-fed resonant slot loaded with a series of PIN diode switches constitutes the fundamental structure of the antenna and the antenna tuning is realized by changing its effective electrical length, which is controlled by the bias voltages of the solid state shunt switches along the slot antenna.
Abstract: In this paper the design of a compact, efficient and electronically tunable antenna is presented. A single-fed resonant slot loaded with a series of PIN diode switches constitute the fundamental structure of the antenna. The antenna tuning is realized by changing its effective electrical length, which is controlled by the bias voltages of the solid state shunt switches along the slot antenna. Although the design is based on a resonant configuration, an effective bandwidth of 1.7:1 is obtained through this tuning without requiring a reconfigurable matching network. Four resonant frequencies from 540-890 MHz are selected in this bandwidth and very good matching is achieved for all resonant frequencies. Theoretical and experimental behavior of the antenna parameters is presented and it is demonstrated that the radiation pattern, efficiency and polarization state of the antenna remain essentially unaffected by the frequency tuning
397 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
TL;DR: A new secret key generation and agreement scheme that uses the fluctuation of channel characteristics with an electronically steerable parasitic array radiator (ESPAR) antenna and has the ability to generate secret keys from the received signal strength indicator (RSSI) profile with sufficient independence is proposed.
Abstract: We describe a secure communication scheme that uses the random fluctuation of the natural environment of communication channels. Only the transmitter and the receiver share the communication channel characteristics. From reciprocity between a transmitter and a receiver, it is possible for them to share one-time information of their fluctuating channel. This can provide a secret key agreement scheme without key management and key distribution processes. In this paper, we propose a new secret key generation and agreement scheme that uses the fluctuation of channel characteristics with an electronically steerable parasitic array radiator (ESPAR) antenna. This antenna, which has been proposed and prototyped, is a smart antenna designed for consumers. Using the beam-forming technique of the ESPAR antenna, we can increase the fluctuation of the channel characteristics. From experimental results, we conclude that the proposed scheme has the ability to generate secret keys from the received signal strength indicator (RSSI) profile with sufficient independence.
348 citations
TL;DR: This paper presents a novel evolutionary optimization methodology for multiband and wide-band patch antenna designs that combines the particle swarm optimization and the finite-difference time-domain to achieve the optimum antenna satisfying a certain design criterion.
Abstract: This paper presents a novel evolutionary optimization methodology for multiband and wide-band patch antenna designs. The particle swarm optimization (PSO) and the finite-difference time-domain (FDTD) are combined to achieve the optimum antenna satisfying a certain design criterion. The antenna geometric parameters are extracted to be optimized by PSO, and a fitness function is evaluated by FDTD simulations to represent the performance of each candidate design. The optimization process is implemented on parallel clusters to reduce the computational time introduced by full-wave analysis. Two examples are investigated in the paper: first, the design of rectangular patch antennas is presented as a test of the parallel PSO/FDTD algorithm. The optimizer is then applied to design E-shaped patch antennas. It is observed that by using different fitness functions, both dual-frequency and wide-band antennas with desired performance are obtained by the optimization. The optimized E-shaped patch antennas are analyzed, fabricated, and measured to validate the robustness of the algorithm. The measured less than - 18 dB return loss (for dual-frequency antenna) and 30.5% bandwidth (for wide-band antenna) exhibit the prospect of the parallel PSO/FDTD algorithm in practical patch antenna designs.
306 citations
TL;DR: In this paper, a reduced size microstrip monopole slot antennas with different slot shapes-straight, L and inverted T, and placed on a small ground plane, are investigated.
Abstract: Reduced size microstrip monopole slot antennas with different slot shapes-straight, L and inverted T, and placed on a small ground plane, are investigated. The ground plane size is 50 mm/spl times/80 mm, which is about the size of a typical PC Wireless card. Detailed simulation and experimental investigations are conducted to understand their behavior and optimize for broadband operation. It is shown that, the variation in the slot shape, from straight to L and T shapes, helps in generating additional resonances, which when coupled to the original resonances of the slot, further increases impedance bandwidths. The bent shapes of the L and T slots reduce their height and provide more space on the ground plane for electronics. A mirror image dual L-slot antenna, placed at two adjacent corners of the ground plane, is also investigated and optimized for the polarization diversity. They provide an impedance bandwidth of 87%, with near orthogonal radiation characteristics. The measured impedance bandwidths (S/sub 11/=-10 dB) of up to 60%, 84%, and 80% are achieved for these straight, L and inverted T slots respectively, by suitably selecting their design parameters. The simulation results are in good agreement with the experimental data considering several practical issues.
TL;DR: In this article, the authors employed one or two L-shape arrays to remove the problem of pair matching between the 2-D azimuth and elevation angle estimation in the propagator method.
Abstract: It is known that computational loads of the propagator method (PM) can be significantly smaller, e.g., one or two order, than those of MUSIC and ESPRIT because the PM does not require any eigenvalue decomposition (EVD) of the cross-correlation matrix and singular value decomposition (SVD) of the received data. However, the PM of the parallel shape array has nonnegligible drawbacks such as 1) requirement of pair matching between the 2-D azimuth and elevation angle estimation which is an exhaustive search and 2) estimation failure problems when elevation angles are between 70/spl deg/ and 90/spl deg/. The purpose of this paper is to show a way to remove these problems in the PM without additional computational loads. This paper will employ one or two L-shape arrays because the parallel shape used in the PM may cause the aforesaid problems. Simulation results verify that the PM with one or two L-shape configurations can remove these problems and improve the performance of the PM significantly, e.g., almost 5 dB in signal to noise ratio for the parameters used in this paper.
TL;DR: In this article, a rectangular waveguide filled with anisotropic uniaxial metamaterial with transversal negative effective permeability was investigated both theoretically and experimentally, and it was shown that such a waveguide supports propagation of the backward wave below the cutoff frequency, thus it can be considered as a dual of the ordinary waveguide.
Abstract: A rectangular waveguide filled with anisotropic uniaxial metamaterial with transversal negative effective permeability is investigated both theoretically and experimentally. It is shown that such a waveguide supports propagation of the backward wave below the cutoff frequency, thus, it can be considered as a dual of the ordinary waveguide. The transversal dimension of this waveguide can be arbitrarily smaller than half of a wavelength in the filling material, provided that the transversal permeability is negative. This peculiar behavior may be used for fabrication of miniaturized rectangular waveguides. Several experimental miniaturized waveguides loaded with double ring resonators in 7 GHz frequency band have been designed, fabricated and tested. The measured results revealed backward-wave passband located below the cutoff frequency. Furthermore, it was experimentally shown that the increase of the physical length of the waveguide caused the decrease of the electrical length. This is a direct proof of the backward-wave propagation since the phase of the backward wave increases along the waveguide.
TL;DR: In this article, a printed wide-slot antenna fed by a microstrip line with a rotated slot for bandwidth enhancement is proposed and experimentally studied, and the measured impedance bandwidth, defined by 10 dB return loss, can reach an operating bandwidth of 2.2 GHz at operating frequencies around 4.5 GHz.
Abstract: In this paper, a printed wide-slot antenna fed by a microstrip line with a rotated slot for bandwidth enhancement is proposed and experimentally studied. Impedance, radiation, and gain characteristics of this antenna are presented and discussed. From experimental results, the measured impedance bandwidth, defined by 10 dB return loss, can reach an operating bandwidth of 2.2 GHz at operating frequencies around 4.5 GHz, which is about four times that of a conventional microstrip-line-fed printed wide-slot antenna. Also, the antenna gain within the operating band is measured and studied, and a 2-dB gain bandwidth of at least 1 GHz is achieved.
TL;DR: It is shown that the singular vectors of the K matrix together with knowledge of the Green function of the background medium in which the targets are embedded lead directly to classical time-reversal based images of the target locations as well as super-resolution images based on a generalized Multiple-Signal-Classification algorithm recently developed for use with the K Matrix.
Abstract: The methods employed in time-reversal imaging are applied to radar imaging problems using multistatic data collected from sparse and unstructured phased array antenna systems. The theory is especially suitable to problems involving the detection and tracking (locating) of moving ground targets (MGT) from satellite based phased array antenna systems and locating buried or obscured targets from multistatic data collected from phased array antenna systems mounted on unmanned aerial vehicles (UAV). The theory is based on the singular value decomposition (SVD) of the multistatic data matrix K and applies to general phased array antenna systems whose elements are arbitrarily located in space. It is shown that the singular vectors of the K matrix together with knowledge of the Green function of the background medium in which the targets are embedded lead directly to classical time-reversal based images of the target locations as well as super-resolution images based on a generalized Multiple-Signal-Classification algorithm recently developed for use with the K matrix. The theory is applied in a computer simulation study of the TechSat project whose goal is the location of MGTs from an unstructured and sparse phased array of freely orbiting antennas located above the ionosphere.
TL;DR: In this paper, a simple and efficient numerical procedure using a singularity cancellation scheme was presented for evaluating singular and near-singular potential integrals with 1/R singularities.
Abstract: A simple and efficient numerical procedure using a singularity cancellation scheme is presented for evaluating singular and near-singular potential integrals with 1/R singularities. The procedure not only has several advantages over singularity subtraction methods, but also improves on some aspects of other singularity cancellation methods such as polar and Duffy transformations. A theoretical analysis is presented for triangles, quadrilaterals, tetrahedrons, bricks, and prisms, and numerical results are presented for triangles and prisms.
TL;DR: In this paper, two different defects, one introduced by the ground plane of the antenna and the other produced by a row of defect rods with different dielectric constants in the EBG structure, are simultaneously used as key controllers of directivity enhancement.
Abstract: We present some applications of an electromagnetic bandgap (EBG) superstrate as a spatial angular filter for filtering undesired radiation by sharpening the radiation pattern. Two different defects, one introduced by the ground plane of the antenna and the other produced by a row of defect rods with different dielectric constants in the EBG structure, are simultaneously used as key controllers of directivity enhancement. Initially, we study the unit cell of the EBG structures by varying several parameters, in order to understand how they influence the locations of the bandgap and defect frequencies. Next, the defect frequencies of the unit cell of the EBG cover, and those with high directivity for the EBG antenna composite, are compared to validate the proposed design scheme. Finally, we introduce some interesting applications of EBG superstrates for various types of patch antennas as spatial angular filters, such as a dual-band orthogonally-polarized antenna, a wide-band directive antenna, and an array antenna with grating lobes.
TL;DR: In this paper, a volumetric metamaterial realization of an artificial magnetic conductor (AMC) is presented, and the performance of a dipole antenna radiating in the presence of this metammaterial AMC is quantified numerically.
Abstract: The design, fabrication and measurement of a volumetric metamaterial realization of an artificial magnetic conductor (AMC) is presented. In contrast to most current realizations of AMCs, such as the mushroom and the uniplanar compact photonic bandgap surfaces, the present design has no perfect electric conductor ground plane. The perfect magnetic conductor properties were designed with capacitively loaded loops for X band operation at 10 GHz. Very good agreement between the numerical and experimental scattering results was achieved. The performance of a dipole antenna radiating in the presence of this volumetric metamaterial AMC is quantified numerically. Resonant interactions of the antenna and metamaterial structure lead to a significant enhancement of the radiated field amplitudes and isolation measured as the front-to-back ratio.
TL;DR: In this paper, a novel approach to realize uniform amplitude time modulated linear arrays with both suppressed sidelobes and sidebands is proposed, which utilizes the direct optimization of the "switch-on" time sequence of each array element via the simple genetic algorithm (SGA).
Abstract: A novel approach to realize uniform amplitude time modulated linear arrays with both suppressed sidelobes and sidebands is proposed. The approach utilizes the direct optimization of the "switch-on" time sequence of each array element via the simple genetic algorithm (SGA). As compared to previous time modulated linear arrays, the new array has the advantages of having low sidelobe level (SLL), low sideband level (SBL) and uniform excitations simultaneously. Experimental results on an experimental prototype of a 16-element printed dipole linear array with the SGA optimized time sequences verified the approach.
TL;DR: In this article, a trident-shaped feeding strip was used to feed a square planar metal-plate monopole antenna with a very wide impedance bandwidth of about 10 GHz (about 1.4-11.4 GHz, bandwidth ratio about 1:8.3).
Abstract: A square planar metal-plate monopole antenna fed by using a novel trident-shaped feeding strip is presented. With the use of the proposed feeding strip, the square planar monopole antenna studied shows a very wide impedance bandwidth of about 10 GHz (about 1.4-11.4 GHz, bandwidth ratio about 1:8.3), which is larger than three times the bandwidth obtained using a simple feeding strip (about 1.5-3.3 GHz, bandwidth ratio about 1:2.3). In addition, the proposed feeding strip can be integrated with the square planar monopole, that is, the feeding strip and the square planar monopole together can be easily fabricated using a single metal plate, making the proposed antenna easy to construct at a low cost. Details of the experimental and simulation results for the proposed planar monopole antenna are presented and analyzed.
TL;DR: In this paper, a slot antenna and a dielectric resonator antenna (DRA) were combined to improve the available bandwidth of a miniaturized antenna without compromising miniaturization or efficiency.
Abstract: The goal of this study is to improve the bandwidth of a miniaturized antenna. The proposed technique combines a slot antenna and a dielectric resonator antenna (DRA) to effectively double the available bandwidth without compromising miniaturization or efficiency. With proper design it is observed that the resonance of the slot and that of the dielectric structure itself may be merged to achieve extremely wide bandwidth over which the antenna polarization and radiation pattern are preserved. In addition, using the DRA, a volumetric source, improves the radiation power factor of the radiating slot. A miniaturized antenna figure of merit (MAFM) is defined to simultaneously quantify aspects of miniaturized antenna performance including the degree of miniaturization, efficiency, and bandwidth. Figures for various common types of antennas are given and compared with that of the proposed structures. In order to determine the effects of varying design parameters on bandwidth and matching, sensitivity analysis is carried out using the finite-difference time-domain method. Numerous designs for miniaturized slot-fed dielectric resonator antennas are simulated and bandwidths exceeding 25% are achieved. Two 2.4 GHz antennas are built, characterized, and the results compared with theory.
Abstract: A novel planar tapered-slot-fed annular slot antenna is proposed in this paper. The antenna utilizes a unique tapered-slot feeding structure and simultaneously possesses ultrawide bandwidth, almost uniform radiation patterns, and low profile. It is, hence, adequate for ultrawide-band (UWB) applications. By means of a normalized antenna transfer function, both frequency domain and time domain characteristics of the antenna are carefully investigated. Two measures, the uniformity related to the radiation patterns and the fidelity associated with the transient behaviors, are used to quantitatively describe the performance of an antenna over such an ultrawide bandwidth. Effects of varying the antenna's geometric parameters on the performance are then investigated. Finally, the influence of minimizing the antenna dimension is discussed at the end of the paper.
TL;DR: In this article, the far-field radiation characteristics of a two-dimensional (2D) periodic leaky-wave antenna (LWA) constructed from a periodic array of metal patches on a grounded dielectric substrate is investigated.
Abstract: The far-field radiation characteristics of a two-dimensional (2-D) periodic leaky-wave antenna (LWA) constructed from a periodic array of metal patches on a grounded dielectric substrate is investigated. A simple dipole source is used as the excitation. Reciprocity together with a periodic spectral-domain method of moments is used to calculate the far-field pattern. Design rules for the scan angle, the substrate dielectric constant, and the periodicity are provided. Finally, a comparison of the 2-D periodic LWA and a dielectric-layer LWA is given to show the similar performance of the two antennas.
TL;DR: In this paper, a method for the efficient derivation of the dispersion equation associated with EBG structures composed by lossless frequency selective surfaces (FSS) printed on stratified dielectric media is presented, valid for the range of frequency where a single propagating Floquet mode occurs.
Abstract: A method is presented, for the efficient derivation of the dispersion equation associated with electromagnetic bandgap (EBG) structures composed by lossless frequency selective surfaces (FSS) printed on stratified dielectric media The method, valid for the range of frequency where a single propagating Floquet mode occurs, is based on Foster's reactance theorem applied to an equivalent transmission line network This theorem implies that the admittance functions of frequency which represent the FSS satisfy the pole-zero analytical properties of the driving point LC admittance functions By these basic properties and by the full-wave identification of the FSS resonances, an analytical form of the dispersion equation is obtained This equation is next solved for both surface wave and leaky wave modes by a conventional numerical technique The results are successfully compared with those from a full-wave analysis
TL;DR: Combined field integral equation (CFIE) is applied for computing electromagnetic scattering by arbitrarily shaped three dimensional dielectric and composite objects in this paper, where the authors present a CFIE formulation which can be used in the analysis of piecewise dielectrics and composite metallic objects with junctions, and properly choosing the coupling coefficients of the equations the conditioning of the discretized matrix equation can be essentially improved and rapidly converging iterative solutions can be obtained even without preconditioning.
Abstract: Combined field integral equation (CFIE) is applied for computing electromagnetic scattering by arbitrarily shaped three dimensional dielectric and composite objects. The objectives of this paper are as follows. First, to present a CFIE formulation which can be used in the analysis of piecewise dielectric and composite metallic and dielectric objects with junctions. Second, to show that properly choosing the coupling coefficients of the equations the conditioning of the discretized matrix equation can be essentially improved and rapidly converging iterative solutions can be obtained even without preconditioning.
TL;DR: In this paper, a half U-slot patch antenna with shorting wall was proposed to reduce the size of the E-shaped patch and showed that the impedance bandwidth, radiation patterns, radiation efficiencies and gains of the half-structures are comparable to the corresponding full structures.
Abstract: The U-slot patch antenna, a single-layer single-patch antenna on a relatively thick substrate (/spl sim/0.08/spl lambda//sub 0/), is a wide-band antenna with an impedance bandwidth in a range of 20%-30%, which is about an order of magnitude larger than that of the regular patch antenna. Recently, it was shown that a half U-slot patch antenna, with half of one of the dimensions of the U-slot patch, maintains similar wide-band behavior. The half-structure was also successfully applied to the U-slot with shorting wall. In this paper, new results on half structures, not previously published, are presented. First, the shorting pin technique is used to reduce the size of the half U-slot patch antenna. By both simulation and experimental studies, it is concluded that the impedance bandwidths, radiation patterns, radiation efficiencies and gains of the half-structures are comparable to the corresponding full structures. Bandwidth of 28.6% and radiation efficiencies exceeding 90% are obtained for the half U-slot patch with shorting pin. Radiation patterns are stable across the matching band. Second, it is shown that a structure obtained from halving the E-shaped patch, which is a derivative of the U-slot patch, also maintains its wide-band behavior.
TL;DR: In this article, a resonator antenna made from a complex artificial surface and a metallic ground plane is described, which is realized using a woodpile electromagnetic bandgap (EBG) material, and the antenna has a frequency dependent reflection plane location.
Abstract: A resonator antenna made from a complex artificial surface and a metallic ground plane is described. The complex surface is realized using a woodpile electromagnetic bandgap (EBG) material, which is shown to have a frequency dependent reflection plane location. A highly directive radiation pattern is created due to the angle-dependent attenuation of the resonator antenna coupling to free space. The antenna has the advantages of low height, low loss, and low sidelobes. It is shown that the directivity can be varied over a fixed range by changing the aperture size of the device, with the maximum directivity determined by both the feed element and EBG material properties. The complete bandgap for the woodpile EBG material is confirmed from a band diagram, and its properties as a complex surface are investigated through transmission calculation and measurement. The design of the antenna is described, and two means of exciting the resonator, a microstrip patch and a double slot, are investigated. Theoretical results for these two antennas are calculated the using finite-difference time-domain and are shown to be in good agreement with measured results.
TL;DR: In this paper, a self-resonant, electrically small electric dipole antenna is presented that exhibits an impedance near 50 Ohms, an efficiency in excess of 95% and a quality factor that is within 1.5 times the fundamental lower bound at a value of less than 0.27.
Abstract: Electrically small antennas are generally presumed to exhibit high impedance mismatch (high VSWR), low efficiency, high quality factor (Q); and, therefore, narrow operating bandwidth. For an electric or magnetic dipole antenna, there is a fundamental lower bound for the quality factor that is determined as a function of the antenna's occupied physical volume. In this paper, the quality factor of a resonant, electrically small electric dipole is minimized by allowing the antenna geometry to utilize the occupied spherical volume to the greatest extent possible. A self-resonant, electrically small electric dipole antenna is presented that exhibits an impedance near 50 Ohms, an efficiency in excess of 95% and a quality factor that is within 1.5 times the fundamental lower bound at a value of ka less than 0.27. Through an arrangement of the antenna's wire geometry, the electrically small dipole's polarization is converted from linear to elliptical (with an axial ratio of 3 dB), resulting in a further reduction in the quality factor. The elliptically polarized, electrically small antenna exhibits an impedance near 50 Ohms, an efficiency in excess of 95% and it has an omnidirectional, figure-eight radiation pattern.
TL;DR: In this article, a small-size directional antenna design for ultrawide-band wireless body area networks/wireless personal area networks applications is presented, which is based on a typical slot antenna structure with an added reflector in order to achieve directionality.
Abstract: This paper presents a novel small-size directional antenna design for ultrawide-band wireless body area networks/wireless personal area networks applications. The design is based on a typical slot antenna structure with an added reflector in order to achieve directionality. The effects of different antenna parameters and human body proximity on the radiation characteristics are analyzed. Antenna measurements with an optic RF setup were performed in order to characterize the small-size antenna far field radiation pattern. The different structural antenna parameters were optimized via extensive numerical simulations. Results show that for frequencies above 3.5 GHz, where the power front-to-back ratio of the directional antenna is greater than 10 dB, its impedance is nearly the same as in the free space. It is not the case neither for the omnidirectional slot antenna nor the monopole antenna next to the body. Between 3 and 6 GHz performance of the novel directional antenna, in terms of radiation efficiency and SAR values, is significantly improved compared to omnidirectional antenna designs.
TL;DR: In this article, a theoretical study on frequency selective surfaces (FSS) with application to artificial magnetic conductors or high-impedance surfaces (HIS) is presented, where a stable resonance was found for the case of series-resonance grids without vias in the slab.
Abstract: The work presented in this paper concerns a theoretical study on frequency selective surfaces (FSS) with application to artificial magnetic conductors or high-impedance surfaces (HIS). Current realizations of HIS are based on a planar FSS at the interface of a metal-backed dielectric slab either including vertical vias or not. A stable resonance was found for the case of series-resonance grids without vias in the slab. The resonance turns out to be unique in theory for all angles of incidence and both polarizations of plane waves illuminating the HIS. It was shown that vias destroy the stabilization effect and introduce a frequency shift. The analytical model was validated by HFSS simulations.