Showing papers in "IEEE Antennas and Propagation Magazine in 2010"
TL;DR: In this paper, the authors present a historical review of the research carried out on dielectric resonator antennas (DRAs) over the last three decades and highlight major research activities in each decade.
Abstract: This article presents a historical review of the research carried out on dielectric resonator antennas (DRAs) over the last three decades. Major research activities in each decade are highlighted. The current state of the art of dielectric-resonator-antenna technology is then reviewed. The achievable performance of dielectric resonator antennas designed for compactness, wide impedance bandwidth, low profiles, circular polarization, or high gain are illustrated. The latest developments in dielectric-resonator-antenna arrays and fabrication techniques are also examined.
494 citations
TL;DR: In this paper, the authors proposed a wideband ultra wideband (UWB) communication protocol with a low EIRP level (−41.3dBm/MHz) for unlicensed operation between 3.1 and 10.6 GHz.
Abstract: Before the emergence of ultra-wideband (UWB) radios, widely used wireless communications were based on sinusoidal carriers, and impulse technologies were employed only in specific applications (e.g. radar). In 2002, the Federal Communication Commission (FCC) allowed unlicensed operation between 3.1–10.6 GHz for UWB communication, using a wideband signal format with a low EIRP level (−41.3dBm/MHz). UWB communication systems then emerged as an alternative to narrowband systems and significant effort in this area has been invested at the regulatory, commercial, and research levels.
452 citations
TL;DR: In this article, an overview of transformation-electromagnetic device design techniques is presented, starting with electromagnetic cloaks that have spherical shell or cylindrical annular shapes, more general cloaking designs of noncircular annular geometries are treated, and the application of cloaking to RF/microwave antenna shielding is also discussed.
Abstract: The recently introduced transformation-electromagnetics techniques provide a new methodology for designing devices that possess novel wave-material interaction properties. They are based on the form invariance of Maxwell's equations under coordinate transformations. These methods provide an extremely versatile set of design tools that employ spatial-coordinate transformations, where the compression and dilation of space in different coordinate directions are interpreted as appropriate scalings of the material parameters. The most famous transformation-optics device is the cloak of invisibility. However, a wide variety of other devices are also possible, such as field concentrators, polarization rotators, beam splitters, beam collimators, and flat lenses. In this paper, an overview of transformation-electromagnetics device design techniques is presented. The paper begins by introducing the underlying design principle behind transformation electromagnetics. Several novel transformation-based device designs are then summarized, starting with electromagnetic cloaks that have spherical shell or cylindrical annular shapes, More general cloaking designs of noncircular annular geometries are treated, and the application of cloaking to RF/microwave antenna shielding is also discussed. Following this, device designs that employ transformations that have discontinuities .on the domain boundary are presented. Unlike those used for cloaks, this type of transformation is capable of modifying the fields outside of the device. Examples of this type of transformation-electromagnetics device are presented, which include flat near-field and far-field focusing lenses, wave collimators for embedded sources (e.g., antennas), polarization splitters and rotators, and right-angle beam benders.
214 citations
TL;DR: The versatility of U-slot patch antennas will be discussed, including: dual-band and tri-band operations, as well as for circular polarization applications.
Abstract: The U-slot patch antenna was originally developed as a single-layer, single-patch wideband antenna. It has recently been shown that it can also be designed to perform a number of other functions. In this paper, a comprehensive account is given on the development of this antenna. Emphasis is placed on experimental and simulation results for various U-slot topologies, illustrating the antenna's versatility in several practical applications. These include wideband, dual- and triple-band operation with small and large frequency ratios, as well as for circular-polarization applications.
158 citations
TL;DR: This paper explains how to exploit GPGPU features by examining how the computational time of the Finite-Difference Time-Domain Method can be reduced.
Abstract: The recent advent of general-purpose graphics-processing units (GPGPUs) as inexpensive arithmetic-processing units brings a relevant amount of computing power to modern desktop PCs. This thus providing an interesting pathway to the acceleration of several numerical electromagnetic methods. In this paper, we explain how to exploit GPGPU features by examining how the computational time of the Finite-Difference Time-Domain Method can be reduced. The attainable efficiency is demonstrated by providing numerical results achieved on a two-dimensional study of a human-antenna interaction problem.
111 citations
TL;DR: In this article, a circularly polarized probe-fed single-layer microstrip-patch antenna with a wideband axial ratio is proposed, which is a modified form of the conventional E-shaped patch, used to broaden the impedance bandwidth of a basic patch antenna.
Abstract: A new technique to achieve a circularly polarized probe-fed single-layer microstrip-patch antenna with a wideband axial ratio is proposed. The antenna is a modified form of the conventional E-shaped patch, used to broaden the impedance bandwidth of a basic patch antenna. By letting the two parallel slots of the E patch be unequal, asymmetry is introduced. This leads to two orthogonal currents on the patch and, hence, circularly polarized fields are excited. The proposed technique exhibits the advantage of the simplicity of the E-shaped patch design, which requires only the slot lengths, widths, and position parameters to be determined. Investigations of the effect of various dimensions of the antenna have been carried out via parametric analysis. Based on these investigations, a design procedure for a circularly polarized E-shaped patch was developed. A prototype has been designed, following the suggested procedure for the IEEE 802.11big WLAN band. The performance of the fabricated antenna was measured and compared with simulation results. Various examples with different substrate thicknesses and material types are presented and compared with the recently proposed circularly polarized U-slot patch antennas.
100 citations
TL;DR: In this paper, the authors investigated the antenna proximity effects for both talk and data modes in mobile phones using an FDTD code and found that the position of the fingers on the handset was more important when close to the antenna, and the palm-handset gap and the index-finger location were the main factors for both absorption and mismatch loss.
Abstract: Based on a recent study of the ways a phone is held (a grip study), CAD models of the human hand have been generated, and antenna proximity effects for both talk and data modes in mobile phones have been investigated using an FDTD code. The simulation results showed that the hand, and especially the index finger, exhibited a major contribution in determining the total loss when compared to the upper torso alone. The influence of the position of the fingers on the handset was found to be more important when close to the antenna. The palm-handset gap and the index-finger location were the main factors for both absorption and mismatch loss. Different data-mode hand phantoms and configurations were investigated, showing that both “overlapped” and “interlaced” grip styles similarly influenced the antenna's communication performance.
77 citations
TL;DR: In this article, the performance properties of several fundamental small-antenna designs are compared as a function of overall length and size (ka), where the antennas operate at or very near the same frequency.
Abstract: In this paper, the performance properties of several fundamental small-antenna designs are compared as a function of overall length and size (ka), where the antennas operate at or very near the same frequency. The objective of this work is to determine which basic design approach or configuration, if any, offers the best performance in terms of: achieving an impedance match; the radiation-pattern shape; the radiation efficiency; the half-power bandwidth; and the 2:1 VSWR bandwidth. The fundamental antenna designs studied here include the spherical folded helix, the cylindrical folded helix, the matched disk-loaded dipole, the matched spherical-cap dipole, and the multi-arm spherical resonator. In addition to discussing the different antenna designs, the fundamental approaches used in impedance matching and optimizing the bandwidth of these small antennas are described. Both numerical simulations and measured results are presented.
70 citations
TL;DR: This paper combines and extends two of the previous works to provide a more complete solution for the GPU acceleration of the Method of Moments, using CUDA by NVIDIA, and serves as a guide for the implementation of other GPU-accelerated computational electromagnetic routines.
Abstract: In this paper, we combine and extend two of our previous works to provide a more complete solution for the GPU acceleration of the Method of Moments, using CUDA by NVIDIA. To this end, the formulations of the original 1982 Rao-Wilton-Glisson paper are revisited, and the scattering analysis of a square PEC plate is considered as a simple example. One of the primary contributions of the paper is to serve as a guide for the implementation of other GPU-accelerated computational electromagnetic routines. As such, this provides a background on general-purpose GPU computation, as well as insight into the finer details of the implementation. The results computed compared well with reference values. From a performance point of view, the GPU implementation was found to be significantly faster. The fastest measured speedup for one of the phases of the Method of Moments computations was more than a factor of 140. This translated into a speedup of about a factor of 45, when the entire Method of Moments solution process for the problem was considered.
64 citations
TL;DR: In this paper, the authors present a review of all known classes of soft and hard hybrid-mode horns, based on the use of a low-index metamaterial liner on the wall.
Abstract: This paper is divided into three parts. Part one gives an overview of the early history of the design and implementation of hard horn antennas, and of the concept formulation of soft and hard electromagnetic surfaces. Part two presents a review of all known classes of soft and hard hybrid-mode horns. Part three presents a new class of hybrid-mode horns, based on the use of a low-index metamaterial liner on the wall. Moment-Method analysis of both soft and hard metamaterial horns indicates that it may be feasible to realize these horns with very large bandwidth. This is because the desired (analyzed) metamaterial dispersion is similar to the Drude dispersion curve (monotonically increasing permittivity as a function of frequency), which represents typical electromagnetic dispersion in dense media. A successful implementation of these horns depends on whether low-index metamaterials can be implemented with polarization-independent boundary impedance, favorable dispersion characteristics, and reasonable loss, mass, and production cost.
62 citations
TL;DR: In this article, the authors revisited the loss phenomenon for a microstrip patch in reflectarray mode, and discussed the reflection characteristics (magnitude and phase) for a reflectarray element with low and high-loss substrates.
Abstract: This paper revisits the loss phenomenon (particularly, the dielectric loss) for a microstrip patch in reflectarray mode, and discusses the reflection characteristics (magnitude and phase) for a reflectarray element with low- and high-loss substrates. First, the dielectric losses that occur in a lossy slab backed by a perfect electric conductor are both analytically and numerically investigated. Using similar numerical analysis, the reflectarray element (a patch on top of a slab backed by a conductor) is characterized, based on dielectric losses and reflection behavior. It is observed that for low-loss substrates, the dielectric loss decreases with increasing substrate thickness (as previously suggested in the literature). More importantly, for high-loss substrates, the dielectric loss no longer follows the expected trend (decreasing loss with increasing substrate thickness). The dielectric loss becomes a complex phenomenon, involving the dielectric loss tangent and substrate thickness. It is therefore noted that it is important to recognize the well-behaved and misbehaved phase-swing region for high-loss substrates for a reflectarray element. A simple circuit-model representation is provided for the reflectarray element. The anomalous phase behavior observed for high-loss substrates is explained using pole-zero analysis. Waveguide measurements are performed to quantify these reflectarray losses for low- and high-loss substrates. Finally, the loss mechanisms in a patch reflectarray (scattering mode) are compared to a patch antenna (radiation mode), using parameters such as reflection power and radiation efficiency, and similar loss mechanisms for both structures are apparent.
TL;DR: The IEEE Antennas and Propagation Society (IAPS) as mentioned in this paper is devoted to the rapid publication of new theoretical and experimental results in all areas of interest to the IEEE.
Abstract: This archival journal is devoted to the rapid publication of new theoretical and experimental results in all areas of interest to the IEEE Antennas and Propagation Society, such as antennas and arrays, wireless propagation, scattering, electromagnetic theory, biomedical applications, electronic properties of materials, high- and low-frequency methods, and numerical techniques in electromagnetics.
TL;DR: The parabolic equation represents one-way propagation, and is widely used in two-dimensional (20) groundwave propagation modeling as mentioned in this paper, taking the Earth's curvature, the atmospheric refractivity variations, non-flat terrain scattering, and the boundary losses into account.
Abstract: Powerful propagation-prediction tools, based on the split-step Fourier-transform and the Finite-Element-Method (FEM) solutions of the parabolic equation (PE) are discussed. The parabolic equation represents one-way propagation, and is widely used in two-dimensional (20) groundwave propagation modeling. It takes the Earth's curvature, the atmospheric refractivity variations, non-flat terrain scattering, and the boundary losses into account. MA TLAB-based numerical split-step parabolic-equation and Finite-Element-Method parabolic-equation routines were developed. These were used in canonical tests and comparisons to illustrate that the parabolic equation accounts for all of these effects. Both tools were calibrated against an analytical exact solution.
TL;DR: In this paper, an analysis of ultra-wideband (UWB) printed planar quasi-monopole antennas using the theory of characteristic modes is presented, and it is shown that the modal voltage-standing-wave ratio, mode current distribution, and modal significance provide deeper physical insight into the operating mechanisms of these popular types of antennas.
Abstract: This paper presents an analysis of ultra-wideband (UWB) printed planar quasi-monopole antennas using the theory of characteristic modes. It is shown that the modal voltage-standing-wave ratio, mode current distribution, and modal significance provide deeper physical insight into the operating mechanisms of these popular types of antennas. Using the printed planar bevel-shaped quasi-monopole antenna as an example, we characterize the antenna's performance. It is found that there are only a few significant modes excited. The dominant mode controls the antenna's behavior over the lower band, while the higher-order modes control the behavior over the upper band. The ground-plane size affects the mode properties. The ground-plane height should be taller than a quarter and shorter or equal to a half-guided-wavelength. The width should be equal to a half-guided-wavelength at the lower-frequency edge. We also examine the notched-frequency characteristics of the antenna by embedding a slot in the monopole. We point out the potential self-interference for the first time. Furthermore, we investigate the miniaturization of the antenna by simply chopping off half of the antenna's structure. We explain why the miniaturized antenna exhibits a wider impedance bandwidth and higher cross-polar radiation at higher frequencies.
TL;DR: In this paper, a comprehensive review of the implementation of these concepts is given, along with performance limits, challenges, mitigation techniques, and open issues in cognitive-radio systems for accurate characterization of operational environments.
Abstract: In order to perform reliable communications, a system needs to have sufficient information about its operational environment, such as spectral resources and propagation characteristics. Cognitive-radio technology has capabilities for acquiring accurate spectrum, location, and environmental information, due to its unique features such as spectrum, location, and environmental awareness. The goal of this paper is to give a comprehensive review of the implementation of these concepts. In addition, the dynamic nature of cognitive-radio systems - including dynamic spectrum utilization, transmission, the propagation channel, and reception - is discussed, along with performance limits, challenges, mitigation techniques, and open issues. The capabilities of cognitive-radio systems for accurate characterization of operational environments are emphasized. These are crucial for efficient communications, localization, and radar systems.
TL;DR: In this paper, a MATLAB-based split-step parabolic-equation (SSPE) propagation package is introduced for the prediction of electromagnetic surface-wave attenuation along multiple mixed irregular and lossy paths.
Abstract: A novel MATLAB™-based split-step parabolic-equation (SSPE) propagation package is introduced for the prediction of electromagnetic surface-wave attenuation along multiple mixed irregular and lossy paths. The impedance boundary condition is implemented via the discrete mixed Fourier transform (DMFT). Irregular terrain modeling is handled via coordinate transformation. Tests are performed along sea paths including smooth and hilly islands. Comparisons with ITU Recommendations and a Finite-Element-Method (FEM) based numerical propagator are given.
TL;DR: In this paper, the generalized Zenneck wave was studied in terms of phase and attenuation properties of different materials (dielectric, epsilon-near-zero, negative-permittivity plasmonic), backward-wave regimes, polarization properties, and singularities that take place when the ratio of the permittivities of the two media is -1.
Abstract: Due to the broad spectrum and versatility of electromagnetics, progress and new discoveries in this field have not made a uniform history. The same and similar phenomena are reinvented by researchers whose interests center on different frequency ranges. Surface waves make an illustrating example. Starting from the works of Sommerfeld and Zenneck, the theory of radio waves over ground was developed during the early and mid-20th century. In the latter part of the century, surface waves were independently studied from the point of view of localization of radiation, in connection with the optical properties of metals. The most-recent development of the present century is that plasmonics and terahertz applications meet microwave studies in the framework of the new discipline of metamaterials. The present article tries to bridge the gaps of surface waves over the various spectral ranges. The paper discusses the properties of the generalized Zenneck wave, including phase and attenuation characteristics of structures with different materials (dielectric, epsilon-near-zero, negative-permittivity plasmonic), backward-wave regimes, polarization properties, and singularities that take place when the ratio of the permittivities of the two media is -1.
TL;DR: In this paper, a planar dipole-based antenna with a small inductive coil was used for mass-retail UHF RFID tag antenna, which is able to work when directly mounted on different materials.
Abstract: This paper presents a novel UHF RFID tag antenna for mass-retailed products. The tag is realized on low-cost material. The antenna is composed of two elements: a planar dipole-based antenna, matched with a small inductive coil. In particular, it is able to work when directly mounted on different materials. When the permittivity or the thickness of the material on which it is mounted changes, the antenna's impedance varies around a fixed impedance on the Smith chart. This impedance is close to the conjugate of the RFID chip's input impedance. The different mounting materials tested were cardboard, a paper block, plastic, wood, a bottle of tap water, and a glass bottle. The measurement results indicated a maximum range of eight meters for materials with a low permittivity, and a maximum range close to two meters for denser materials or materials with a higher permittivity.
TL;DR: In this article, it was shown that the far field region of antennas radiating with either polarizations located over a ground plane starts at a distance 2H2/λ (here, H ≫ L), where L is the effective size of the antenna, and λ is the wavelength.
Abstract: In this paper, we look at the characterization of the far-field regions of antennas located over a ground plane. For antennas radiating in free space, the far field starts at a distance 2L2/λ, where L is' the effective size of the antenna, and λ is the wavelength. The question now is if this same radiating antenna is placed at a height H over a ground plane, then where does the far field of that antenna start? The goal of this paper is to demonstrate that for antennas radiating with either polarizations located over a ground plane, the far field starts at a distance 2H2/λ (here, H ≫ L). We illustrate the validity of some rules of thumb through numerical simulations, and by using the definition of the far field as the region where the radial component of the field is negligible compared to the other components, and for regions where the ratio of the electric field to the magnetic field is characterized by η, the characteristic impedance of free space. We also look at the validity of this rule of thumb when antennas are located over an imperfect ground plane. Finally, we examine the phenomenon of height-gain in wireless cellular communications. We illustrate that under the current operating scenarios, where the base-station antennas are deployed over a tall tower, the field strength actually decreases with the height of the antenna over a realistic ground, and there is no height gain. Therefore, to obtain a scientifically meaningful operational environment, the vertically polarized base-station antennas should be deployed closer to the ground. When deploying antennas over tall towers, it may be more advantageous to use horizontally polarized antennas than vertically polarized antennas for communication in cellular environments. Numerical examples are presented to illustrate these cases.
TL;DR: In this article, an estimation of the gain enhancement of a microstrip patch that occurs when a standard PTFE substrate is replaced by air is presented, and the theory is verified for a wide range of antenna dimensions, using some measured and simulated data, indicating very close agreement amongst the data.
Abstract: An easy estimation of the gain enhancement of a microstrip patch that occurs when a standard PTFE substrate is replaced by air is presented. The theory is verified for a wide range of antenna dimensions, using some measured and simulated data, indicating very close agreement amongst the data. This approach should be very handy and useful to a designer dealing with air-substrate microstrip antennas.
TL;DR: In this article, the authors present simulations and measurements of a reflector system that can rapidly scan a terahertz beam for a high-resolution standoff-imaging application, without compromising the beam quality.
Abstract: In this contribution. we present simulations and measurements of a reflector system that can rapidly scan a terahertz beam for a high-resolution standoff-imaging application, without compromising the beam quality. The antenna system utilizes a Gregorian confocal-reflector geometry, with a small mechanical rotating mirror. The system has been successfully fabricated and tested, with THz imagery of targets at a 25 m standoff range being obtained In five seconds. for the current configuration. We also describe how frame rates exceeding 2 Hz can be achieved using a heterodyne array of just a few elements, with or without a multiplexing technique.
TL;DR: In this paper, the design, analysis, and development of waveguide-fed planar slot arrays to achieve low-average-sidelobe specifications, as may arise in radiometer applications, are discussed.
Abstract: This paper discusses the design, analysis, and development of waveguide-fed planar slot arrays to achieve low-average-sidelobe specifications, as may arise in radiometer applications. Such antennas may be required to meet strict average sidelobe levels in different angular regions, and low average return loss over a specified bandwidth. In addition to Elliott's design technique, we used a Moment-Method analysis program, Ansoft's HFSS code, and results of tolerance studies using Monte Carlo simulations to meet the design objectives. Comparisons of simulated results and experimental results are also presented.
TL;DR: It is shown that for the best performance, non-planar GPS antennas should have a convex surface, a large curvature, and as many elements as possible.
Abstract: The effects of various design parameters (e.g., the curvature, number of elements, and element distribution) on the anti-jamming (AJ) performance of non-planar GPS antenna arrays are discussed. It is shown that for the best performance, non-planar GPS antennas should have a convex surface, a large curvature, and as many elements as possible. The antenna elements should also be distributed to fill the available surface. Using these guidelines, a six-inch-high. non-planar GPS antenna containing seven elements was designed, and an experimental model of the antenna was built. The anti-jamming performance of the experimental antenna is presented.
TL;DR: An accurate simulation of the radiation performance of a commercial CAD-oriented slide mobile phone, taking into account the influence of the SAM (specific anthropomorphic mannequin) head and hand is presented.
Abstract: An accurate simulation of the radiation performance of a commercial CAD-oriented slide mobile phone, taking into account the influence of the SAM (specific anthropomorphic mannequin) head and hand, is presented. The simulation was performed using the commercial software SEMCAD, which is based on the Finite-Difference Time-Domain (FDTD) Method. The radiation effect on the SAM head and hand close to the phone was also investigated. Throughout the numerical simulations, the return loss, the radiation efficiency, and the near-field distribution of the mobile phone could be obtained, and thus the impact on the human body could be estimated. The slide phone was measured under different conditions. Numerical results were compared with the measurement data, and good agreement was obtained.
TL;DR: In this article, the authors provide an overview of two such designs: linear polyfractal arrays and planar arrays of aperiodic tilings, and show that the benefits of these methodologies are amplified when applied to larger sized array designs (Le., arrays with larger element counts).
Abstract: Over the past few decades, much research has been invested in the exploration of wideband and ultra-wideband (UWB) antenna arrays. The goals of such array designs are to determine the best element arrangements, which yield radiation patterns possessing the highest degrees of side lobe suppression, and no grating lobes over the largest possible operating bandwidths. It has been recently shown that nature-inspired array-design methodologies can provide solutions that exhibit these ultra-wideband characteristics. This article provides an overview of two such designs: linear polyfractal arrays, and planar arrays of aperiodic tilings. Robust nature-inspired genetic-algorithm optimization techniques were utilized in the design of both types of arrays in order to obtain the best-possible UWB performance. This article also discusses the fabrication and experimental validation of two 32-element linear polyfractal array-design prototypes, which exhibited close agreement to the radiation performance predicted by simulation. These experimentally validated arrays possessed wide bandwidths with suppressed grating lobes and relatively low sidelobes for their size (-16.3 dB at f0 and -5.39 dB at f0)Additional simulations discussed in this paper showed that the benefits of these methodologies are amplified when applied to larger sized array designs (Le., arrays with larger element counts). One example exhibited a peak sidelobe level less than -19.34 dB over a 40:1 bandwidth.
TL;DR: In this article, a triple-band rectangular microstrip antennas using combinations of an open-circuit nearly-quarter-wavelength stub, a resonant U-slot, and a pair of rectangular slots are proposed.
Abstract: Triple-band rectangular microstrip antennas using combinations of an open-circuit nearly-quarter-wavelength stub, a resonant U-slot, and a pair of rectangular slots are proposed. A new configuration for a tour-band antenna has been realized by cutting two half U-slots inside a stub-loaded rectangular microstrip patch. The multi-port network models for these antennas are also proposed, which help in analyzing the mode distributions at various frequencies. The multi-band response has been experimentally verified, and close agreement was obtained among the simulated, measured, and theoretical results.
TL;DR: In this article, a near-field/far-field (NFFF) transformation approach is proposed for characterizing planar aperture antennas from planepolar scanning data, where the radial and azimuthal field sampling spacings are chosen to provide the minimum number of nearfield samples, optimizing the singular-value dynamics of the relevant linear operator connecting unknowns and data.
Abstract: We develop a near-field/far-field (NFFF) transformation approach for characterizing planar aperture antennas from planepolar scanning data The radial and azimuthal field-sampling spacings are chosen to provide the minimum number of nearfield samples, optimizing the singular-value dynamics of the relevant linear operator connecting unknowns and data A numerical and experimental analysis is provided, showing how the approach is capable of significantly reducing both the number of required samples and the number of measurement rings, as compared to the advanced sampling techniques available in the literature
TL;DR: In this article, the photonic probe allows AUT-probe distances of less than one wavelength, which drastically reduces test-range and scanner dimensions, improves the signalto-clutter ratio and the signal-to-noise ratio, and reduces the scanning area and time.
Abstract: We present innovative near-field test ranges, named compact-near-field (CNF) and very-near-field (VNF). These use photonic probes, and advanced near-field far-field (NFFF) transformations from amplitude and phase (complex) or phaseless measurements. The photonic probe allows AUT-probe distances of less than one wavelength. This drastically reduces test-range and scanner dimensions, improves the signal-to-clutter ratio and the signal-to-noise ratio, and reduces the scanning area and time. In both the cases of complex and phaseless measurements, the neat-field-to-far-field transformation problem is properly formulated to further improve the rejection of clutter, noise, and truncation error. The advantages of the compact-near-field and very-near-field test ranges are discussed and numerically analyzed. Experimental results are presented for both planar and cylindrical scanning geometries.
TL;DR: The requirements for a GPS landing system reference antenna are reviewed, the design principles for the ARL-1900 antenna are presented, its implementation is described, and performance data is presented.
Abstract: The GPS landing system (GLS) is a reality today, and will undoubtedly become the workhorse system in the future. GPS aircraft navigation is currently utilized for aircraft en-route, terminal, and initial-approach navigation. It is expected that in 2009, a Category I GPS landing system will start its initial phase of a worldwide deployment. The ARL-1900 antenna was designed specifically to satisfy the stringent requirements for the Category I, II, and III GPS landing system reference-receiver stations. A difficult problem for a Category I, II, and III GPS landing systems is the mitigation of ground-reflected multipath effects. The antenna must provide coverage of the upper hemisphere while suppressing ground-reflected multipath. In addition, the antenna must operate at the L1, L2, and L5 GPS frequencies, have right-hand circular polarization, and ideally have constant carrier and code (group) delay throughout the coverage region. Over a period of 15 years, BAE Systems has developed the ARL-1900 antenna, a unique antenna with near-ideal performance that satisfies the stringent requirements for a Category I, II, and III GPS landing systems. This paper reviews the requirements for a GPS landing system reference antenna, presents the design principles for the ARL-1900 antenna, describes its implementation, and presents performance data.
TL;DR: In this article, the authors introduced the concept of the time-reversal electromagnetic chamber (TREC), a new facility for creating coherent wavefronts within a reverberation chamber, which is shown to also be a useful tool for the characterization of the field radiated by an antenna under test (AUT).
Abstract: In a recent paper, we introduced the concept of the time-reversal electromagnetic chamber (TREC), a new facility for creating coherent wavefronts within a reverberation chamber. This facility, based on the use of time-reversal techniques in a reverberating environment, is shown here to also be a useful tool for the characterization of the field radiated by an antenna under test (AUT). The time-reversal electromagnetic chamber has proven to be capable of providing real-time measurements, with accuracy typically better than 1 dB over the main Iobes, while using a limited number of static probe antennas. This performance is made possible by taking advantage of the reflections over the chamber's walls in order to gain access to the field radiated along all directions, with no need to mechanically displace the probes, or to have a full range of electronically switched probes. A two-dimensional numerical validation supported this approach, proving that the proposed procedure allows the retrieval of the free-space radiation pattern of the AUT.