Showing papers in "IEEE Antennas and Propagation Magazine in 2020"

Rectennas for Radio-Frequency Energy Harvesting and Wireless Power Transfer: A Review of Antenna Design [Antenna Applications Corner]

Abstract: Radio-frequency (RF) energy harvesting (RFEH) and radiative wireless power transfer (WPT) have attracted significant interest as methods of enabling battery-free sustainable wireless networks. Rectifying antennas (rectennas) are the cornerstone of WPT and RFEH systems and critically affect the amount of dc power delivered to the load. The antenna element of the rectenna directly impacts the radiation-to-ac harvesting efficiency, which can vary the harvested power by orders of magnitude. In this article, antenna designs employed in WPT and ambient RFEH applications are reviewed. Reported rectennas are categorized based on two main criteria: the antenna-rectifier impedance bandwidth and the antenna's radiation properties. For each criterion, the figure of merit (FoM) is identified for different applications and reviewed comparatively.

Electromagnetic Chirality, Part 1: The Microscopic Perspective [Electromagnetic Perspectives]

Abstract: This article is the first in a two part article (the second part [1] will be published in an upcoming issue of IEEE Antennas and Propagation Magazine ) that presents a bottom-up description of electromagnetic chirality, which occurs in materials composed of particles with structural handedness (see "Side Note 1").

Wireless Passive Sensors for Food Quality Monitoring: Improving the Safety of Food Products

Abstract: Food waste amounts to roughly one-third of its total production every year. There is an unprecedented demand to improve long-term storage of food products while preserving quality and safety in every stage of its processing, from postharvesting to preconsumption. Different technologies, such as total viable count (TVC), metal-oxide-semiconductor sensors, fluorescence spectroscopy, dye and polymer-based colorimetric sensors as well as radio-frequency identification (RFID), are currently applied for monitoring food products. This article provides an overview of current developments in near-field and ultrahigh frequency (UHF) wireless passive sensors for monitoring of food quality indices and food spoilage indicators. Solutions based on coupled-coil resonator and UHF chipless RFID sensors with application to bacterial-count detection, volatile gas concentration, humidity, and pH monitoring are highlighted.

Noninvasive Inline Food Inspection via Microwave Imaging Technology: An Application Example in the Food Industry

Abstract: Contamination with foreign objects is one of the main causes of customers? complaints against food manufacturers. Although different technologies are used for food and beverage inline monitoring, cases of contaminated food products still reach the market, many of which involve plastic and glass fragments. In this article, we propose the use of a microwave imaging (MWI) technology to monitor packaged foods along production lines. In this framework, MWI exploits the differences in dielectric properties between the food and the contaminant as well as the differences between faulty and unaltered items. A dedicated MWI system is designed and validated through numerical simulations. Then the prototype device is assessed experimentally, both in controlled laboratory conditions and on an industrial production line. The results of this study show the capabilities of this technology for food safety and security.

A Compact CubeSat Antenna With Beamsteering Capability and Polarization Agility: Characteristic Modes Theory for Breakthrough Antenna Design

Abstract: In this article, we propose a novel compact radiating system for a 1 U CubeSat. The designed antenna benefits from characteristic modes theory (CMT), which provides guidelines to advantageously exploit the hosting platform as part of the radiating system. The effect of the small satellite on the resonance frequency and pattern shape is therefore intrinsically taken into account. The employed inductive-coupling exciters are nonresonant half-loops that offer a huge saving in terms of space and weight requests. Additionally, the proposed S-band antenna provides the remarkable feature of scan-beam capability, in circular polarization (CP) as well as linear polarization (LP), which is not found in any other compact radiator. The overall angular coverage spans more than 90d with an axial ratio (AR) lower than 3 dB and within the half-power beamwidth (HPBW), and therefore a 360d angular coverage is guaranteed if four of these minimally invasive radiators are placed on the small satellite. Measurements are in positive agreement with simulations and confirm the estimated good performance of this innovative solution.

Absorptive Frequency-Selective Reflection/Transmission Structures: A Review and Future Perspectives

Abstract: Absorptive frequency-selective reflection/transmission (AFSR/T) structures, which have been recently described in the literature, are different from traditional frequency-selective structures (FSS) due to their unique responses. The AFSR structure has a reflection band with one- or two-sided absorption bands, while the AFST structure has a transmission band within a wide absorption band. In this article, we present a comprehensive literature review, demonstrate new designs, and propose future perspectives. The review of AFSR structures is divided into several parts: structures with single and multiple reflection bands, structures that use lumped resistors and commercial absorbers, and structures integrated with an antenna to achieve an antenna system with a low out-of-band radar cross section (RCS). For AFST structures, the review is mainly concerned about their response through the use of one-sided upper/lower absorption bands, two-sided absorption bands, and a tunable design. In addition, the techniques used in the literature to bypass losses are mentioned. The limitations of the reported structures are listed, and future perspectives are provided at the end of this article.

Wearable Chipless Radio-Frequency Identification Tags for Biomedical Applications: A Review [Antenna Applications Corner]

Abstract: Wearable sensing technology and body-centric wireless systems have received widespread attention due to their tremendous prospective in e-health, the Internet of Things (IoT), and smart cities. Low-cost textile antennas for body-centric radio-frequency identification (RFID) sensing technology are the future for such wearable sensing systems. The antennas can sustain bending and stretching and offer a maintenance-free communication link with the human body, environment, and IoT infrastructure. Its sensing technology provides the seamless real-time wireless monitoring of important physiological signals. Understanding its significance in emerging applications, this article reviews wearable passive RFID tag sensors that monitor various physical parameters. The primary goal of these research works is to design RFID sensors and test their performances in various environmental conditions. Chip-based RFID sensors are too expensive for mass deployment, hence, chipless RFID tag sensors have become a low-cost and maintenance-free alternative, addressing market demands for the emerging IoT, where trillions of such sensors will be used. Observing the significance of the technology, a few important design parameters, such as tag radar cross section (RCS) and various form factors of tag antennas, are examined in this article. The article also presents some emerging applications of the developed sensors.

Calibration and Direction-of-Arrival Estimation of Millimeter-Wave Radars: A Practical Introduction

Abstract: Have you read everything about direction-of-arrival estimation in textbooks but are still uncertain how to realize it in practice? This tutorial-like article will help to link the theory with a practical approach for direction-of-arrival estimation using millimeter-wave (mm-wave) radar systems, and it deals with arising challenges. Step by step, it is explained how to move from the measured time domain data to the estimated angular position of the target. Since the target angle estimation is usually carried out after range-velocity processing, the required preprocessing steps are described.

Innovations in Electromagnetic Imaging Technology: The Stored-Grain-Monitoring Case

Abstract: The evolution of the electromagnetic imaging technology that has enabled the quantitative imaging of the complex-valued permittivity of grains stored in silos is reviewed. The main innovations that have contributed to the advancement of electromagnetic imaging technology and facilitated the development of this particular application are described. These innovations relate to electromagnetic inverse scattering algorithms and the associated numerical inversion models, data acquisition systems that collect field information within grain-filled silos, and calibration techniques that bridge the gap that the modeling error creates between the inversion model and the actual system within which the scattered-field data are being collected. Although the particular case of storedgrain monitoring is used to highlight the need for the innovations that are described, these advances in electromagnetic imaging technology are applicable to-and, indeed, have been applied to-other areas, such as biomedical imaging for the detection of breast cancer.

Compact Dual-Band Metamaterial-Based High-Efficiency Rectenna: An Application for Ambient Electromagnetic Energy Harvesting

Abstract: A compact composite right/left-handed (CRLH)-based dualband rectenna is proposed for electromagnetic (EM) energy harvesting at the operating frequencies of Wi-Fi (2.5 GHz) and Worldwide Interoperability for Microwave Access (WiMAX) (3.6 GHz) bands. The rectenna consists of a dual-band antenna and dual-band rectifier. The antenna is realized in a microstrip topology using a balanced CRLH transmission line (TL) with an open termination. It measures 0.36 # 0.2 # 0.00049 mo (mo is the free-space guided wavelength) at 2.5 GHz and operates at 2.5 and 3.6 GHz, with an operating bandwidth of 4.75 and 3.3%, respectively, and a peak gain of 2.6 decibels relative to isotropic (dBi) at 2.5 GHz and 1.6 dBi at 3.6 GHz. The dual-band rectifier is designed using a novel CRLH-based microstrip topology composed of microstrip lines and lumped components. The overall rectifier volume is 0.3 # 0.2 # 0.0005 mo at 2.5 GHz. The measured radio-frequency (RF)?dc conversion efficiency is more than 59% at 2.5 GHz and 41% at 3.6 GHz, for an input power of 2 dB milliwatts (dBm) in both cases.

Dielectric Properties of Common Building Materials for Ultrawideband Propagation Studies [Measurements Corner]

Abstract: Signal propagation is affected by the characteristics of the materials in the medium. Therefore, information about material properties is of paramount importance when radio propagation is investigated. In this article, the measured complex relative permittivity of 20 common materials in indoor environments (including plastics, wood and woodbased materials, glass, gypsum plaster and plasterboard, brick, and concrete) across the frequency band of 0.2-67 GHz is shown. The dielectric properties are measured by using two open-ended coaxial probes. The single-pole Cole-Cole model is employed for fitting the measured data since most of the materials follow it. Moreover, fitting parameters for the multipole Debye model, which can be used instead of the Cole-Cole [it is more appropriate for finite-distance, timedomain (FDTD) applications], are given. Thus, an easy way for obtaining the data is provided, which can be helpful when wideband propagation is considered.

Vanadium Dioxide for Reconfigurable Antennas and Microwave Devices: Enabling RF Reconfigurability Through Smart Materials

Abstract: We present a comprehensive study of a new method to reconfigure, tune, and/or program antennas and radio-frequency (RF) devices. The method consists of using electrical signals to induce the solid-tosolid phase transition in vanadium dioxide (VO2) thin-film patterned structures that connect the device metallization layer with extensions, thus effectively changing the geometry of the device. Applied voltage pulses to a resistive heater electrically isolated from the antenna metallization layers increase the temperature of the VO2 strip across the phase transition. Hence, the VO2-biasing mechanism and the antenna are electrically decoupled, which enables an additional degree of freedom for antenna and microwave device engineers as the reconfiguration is no longer restricted by any biasing network limitations. Radiation patterns are also maintained unaffected. This decoupling adds into the design spectrum, applications that require wideband tuning, low-loss structures (e.g., arrays and reflectarrays), and even reconfigurable cloaks. The VO2 switch is arguably the smallest ever used to reconfigure an antenna, which requires further circuit element considerations. The presented method is validated through a series of antenna prototypes that demonstrate VO2 applicability on wire and aperture antennas. Details and challenges of the monolithic integration of VO2 thin films and resistive heaters for reconfigurable antennas, along with the measurement setup, are presented. Results unveil this new reconfiguration technique and suggest further applications, as the VO2 may also be activated optically.

The Design of a Trimodal Broadside Antenna Element for Compact Massive MIMO Arrays: Utilizing the Theory of Characteristic Modes

Abstract: Massive multiple-input, multiple-output (MIMO) arrays are becoming critical elements in cellular base station infrastructure. We utilize the theory of characteristic modes (TCM) to design a novel trimodal broadside antenna element that is suitable for constructing compact massive MIMO arrays. The proposed antenna element consists of three ports, formed by reviewing an existing compact two-port Y-shaped patch antenna from a TCM perspective. Using this perspective, the Y-shaped antenna is modified into a snowflake-shaped patch antenna and excited by three ports via capacitive coupling. The advantage of this design approach is that the size of the three-port antenna is approximately the same as a conventional dual-polarized patch antenna, hence allowing 50% more antenna elements for the same array aperture. By cutting the ground plane into a hexagonal shape, a multiple of the proposed three-port canonical antennas are concatenated together to form 21- and 102-port massive MIMO arrays with all radiation patterns pointing in the broadside direction. Key performance characteristics of the massive MIMO arrays, i.e., the Hermitian product of the simulated massive MIMO channel and mutual coupling, validate the effectiveness of the compact design.

Radio-Frequency-Identification-Based Intelligent Packaging: Electromagnetic Classification of Tropical Fruit Ripening

Abstract: Intelligent packaging for food continuously generates informative digital/analog content about the contained products during their entire life span, thus becoming one of the enabling elements of the modern data-driven economy. Packaging shells for fruits, augmented with low-cost wireless sensors for the automatic estimation of the ripening grade, can reduce waste, optimize shelf exposure, suggest when produce should be consumed, and engage customers through enhanced user experiences. Radio-frequency identification (RFID) with sensorless, low-cost labels, empowered with electromagnetic-based intelligence and automatic classification tools, may stimulate the widespread diffusion of this technology. Focusing on avocados, this article presents an experimental characterization of RFID's complex permittivity along with ripening and a near-field numerical model of a passive RFID interrogation system with tagged fruit, aimed at extracting the variation of electromagnetic metrics of the RFID link during ripening. The results are used to design and fabricate an RFID totem for avocado monitoring that, coupled with a properly trained binary tree classifier, is capable of recognizing up to three ripening levels of packaged fruits, with an overall accuracy higher than 85% even if the task is executed by unskilled operators.

Electromagnetic Chirality, Part 2: The Macroscopic Perspective [Electromagnetic Perspectives]

Abstract: This article is the second part of a two-part article that presents a bottom-up description of electromagnetic chirality, which occurs in materials composed of particles with structural handedness.

Nondestructive Control of Fruit Quality via Millimeter Waves and Classification Techniques: Investigations in the Automated Health Monitoring of Fruits

Abstract: Fast and efficient nondestructive evaluation (NDE) methods for food control is still an ongoing field of research. We have recently proposed to combine W-band imaging with nonlinear support vector machine (SVM) classifiers to sort out healthy from damaged fruits for a single variety of fruit. We have tested it on apples and peaches separately with a mean accuracy of 96%. We have also shown the limitation of a biclass SVM since it has failed to sort healthy from damaged fruits when the set of fruits was composed of a mix of apples and peaches. In this article, we continue to explore the capability of SVM associated with millimeter-wave (mm-wave) low-terahertz (THz) measurements. First, we tackle the problem of classifying a mix of fruits with a multiclass SVM using the Digital Binary Tree architecture. With this method, the error rate does not exceed 2%. Secondly, we move from the W- to D-band (lowTHz). The main reason is the increase of the lateral resolution and the possibility to have more compact systems in the view of an industrial deployment. We start our D-band investigations with range measurements to estimate the average permittivity of the apple in this frequency bandwidth. We have found a drastic decrease compared to the microwave region. It is consistent with the behavior of the water, which is one of the main components of the apple. Then we trained the SVM with the D-band database and finally performed the classification on unknown samples and obtained an accuracy of 100%.

A Metasurface Wall for Isolation Enhancement: Minimizing mutual coupling between MIMO antenna elements

Abstract: A p45d, dual-polarized, high-isolation, 1 t 2 multiple-input, multiple-output (MIMO) antenna array for wideband microbase-station application is presented in this article. The proposed antenna element incorporates two perpendicular magnetic coupling feeding (MCF) networks and an H-shaped slot in the ground plane to improve the port isolation. Simulation results indicate that it has an isolation of more than 38 dB. To suppress the mutual coupling between antenna elements, a dual wall consisting of a novel metasurface structure is introduced. When spatial-wave incidents occur, the isolation wall can restrain the electromagneticwave propagation. The electromagnetic waves produce resonance on the wall surface, which scatters some of the resonance, while the rest is transmitted to the ground and weakened by the decoupling structure between two elements. The metasurface walls, which are inserted vertically between the antenna elements, improve the isolation by roughly 5.9 dB within the 2.5-2.7-GHz frequency band and reach a maximum of -22.8 dB at approximately 2.6 GHz. The proposed antenna has been fabricated, and the experimental results are near the simulation responses.

A Space Debris-Dedicated Channel for the P-Band Receiver of the Sardinia Radio Telescope: A Detailed Description and Characterization

Abstract: Space debris (SD) is an important problem for space operations and a hot topic for space surveillance research. A structured network of radar sensors is available worldwide, offering vital information about debris status. Recently, the Sardinia Radio Telescope (SRT), a 64-m dish located in Sardinia, Italy, was introduced in the European plan for SD monitoring. Because the SRT is devoted to radio astronomy applications and is not optimized for SD echo detection, the need for an SD-dedicated channel has emerged. In this article, we present a detailed description and characterization of the new P-band receiving chain for SRT's space debris-monitoring purposes. As a test of its capabilities, the new channel was used to detect the echoes that emanated from the Chinese space station Tiangong-1 when it reentered Earth's atmosphere on its latest mission.

Wireless on Walls: Revolutionizing the Future of Health Care

Abstract: Following the standardization and deployment of the 5G network, researchers have shifted their focus to beyond 5G (B5G) communication. Existing technologies have brought forth a plethora of applications that could not have been imagined in the past years. B5G will enable us to rethink the capability it will offer in various sectors, including agriculture, search and rescue, and, more specifically, in the delivery of health-care services. Unobtrusive and noninvasive measurements using radio-frequency (RF) sensing, monitoring, and the control of wearable medical devices are the areas that would potentially benefit from B5G. Applications such as RF sensing, device charging, and remote patient monitoring will be a key challenge in using millimeter-wave (mm-wave) communication. The mm-waves experience multipath-induced fading, where the rate of attenuation is larger as compared to microwaves. Eventually, mm-wave communication systems would require range extenders and guided surfaces. A proposed solution is the use of intelligent reflective surfaces, which will have the ability to manipulate electromagnetic (EM) signals. These intelligent surfaces mounted and/or coated on walls, also known as intelligent walls (IWs), are planar and active surfaces, which will be a key element in B5G and 6G communication. These intelligent walls, equipped with a machine learning (ML) algorithm and computation power, would have the ability to manipulate EM waves and act as gateways in the heterogeneous network environment. The article presents the application and vision of intelligent walls for next-generation health care in the era of B5G.

Enabling the Internet of Things With CubeSats: A Review of Representative Beamsteerable Antenna Concepts

Abstract: The advent of CubeSats has empowered the vision of using a satellite constellation to provide seamless Internet coverage across the globe. This vision, known as the Internet of Space (IoS), is the key enabler of the Internet of Things (IoT). One of the major challenges in making IoS a reality is the development of an antenna system that can sustain a high data-rate link while being amenable to integration with the small CubeSat form factor. This challenge is further magnified by the requirement that the antenna dynamically reconfigures its radiation pattern to illuminate geographical areas that demand more coverage. The aim of this article is to provide an overview of antenna concepts developed by representative researchers that can overcome these challenges. If properly tailored for specific CubeSat applications, these concepts can make CubeSat-based IoS a realizable vision. We also highlight the open challenges and technology gaps that future research must address to make IoT a reality.

From Visual Spectrum to Millimeter Wave: A Broad Spectrum of Solutions for Food Inspection

Abstract: The consequences of food adulteration can be far reaching. In the past, inexpensive adulterants were used to inflate different products, leading to severe health issues. Contamination of food has many causes and can be physical (plant stems in tea), chemical (melamine in infant formula), or biological (bacterial contamination). Employing suitable sensor systems along the production process is a requirement for food safety. In this article, different approaches to food inspection are illustrated, and exemplary scenarios outline the potential of different sensor systems along the spectrum.

An Extremely Large Ka-Band Reflectarray Antenna for Interferometric Synthetic Aperture Radar: Enabling Next-Generation Satellite Remote Sensing

Abstract: The Surface-Water Ocean Topography (SWOT) mission, currently in development at NASA?s Jet Propulsion Laboratory (JPL), will employ the Ka-band radar interferometer (KaRIn) to characterize the ocean's height at the unprecedented spatial resolution of 2 km and is designed to provide a global inventory of significant terrestrial water bodies [area g(250 m)2] and rivers (width g50-100 m). The key enabling technology for this instrument is a pair of large, deployable antennas that form the interferometer. This article describes the development of the largest reflectarray antenna currently in process for a spaceflight application: a 5 ? 0.26-m offset-fed reflectarray antenna with a 4.37-m focal length. It details critical aspects of the development, including the radio-frequency (RF) design and analysis, fabrication, and measurement, and discusses unique requirements imposed by the interferometer that resulted in significant design and verification challenges. Flight-hardware measurements demonstrated a gain of approximately 49.5 dB, corresponding to an efficiency of 52%, and an azimuth beamwidth of 0.105?, with a beam-pointing knowledge of 5 millidegrees. Accurate characterization of these antenna-performance parameters is critical to the success of the KaRIn instrument.

Substrate-Integrated-Waveguide Power Dividers: An Overview of the Current Technology

Abstract: Power dividers are important components of microwave/millimeter wave (mm-wave) circuit design. This article provides a comprehensive review of the state-of-the-art substrate-integrated-waveguide (SIW) power dividers/combiners. SIW technology converts waveguide-like structures into planar form, compensates for the drawbacks of microstrip structures at higher-frequency circuit designs, and minimizes production complexity and costs compared to conventional waveguide structures. An overview of how traditional dividers have progressive adopted the SIW technique is presented and a comparative performance analysis of the divider types and practical paradigm show the future potential of SIW technology.

Aspects of Quantum Electrodynamics Compared to the Classical Case: Similarity and Disparity of Quantum and Classical Electromagnetics

Abstract: In this article, aspects of quantum electromagnetics (QEM) are discussed with a view toward illustrating basic concepts and making some connections with classical EM. The similarities and differences between the mathematical representations as well as the physical interpretations in the quantum and classical cases are reviewed, and a brief discussion of the different objectives and quantities to be measured/computed in quantum and classical regimes is provided. The role of the classical Green function in rigorous, fully quantum electrodynamics (QED) is highlighted, and an example of quantum state evolution in a graphene environment is presented.

Electromagnetic Imaging and Sensing for Food Quality and Safety Assessment [Guest Editorial]

Abstract: The six articles in this special present to the antennas and propagation community some of the emerging research activities on the application of EM-based technologies in such a societally relevant topic. The articles address food industry applications as different as sensing food quality and food spoilage indicators and monitoring food items to detect contaminants.

Evaluation of the Frequency Bandwidth and Gain Properties of Antennas: Characteristics of Circularly Polarized Microstrip Antennas

Abstract: Frequency bandwidth, gain, and dimensions are some of the most important characteristics of antennas. A comparison of the most important characteristics of circularly polarized microstrip antennas (CP MSAs) [1]-[33], using traditional methods, is accomplished in this article. The CP MSAs were chosen for the study because MSAs have been the most dynamically developing field of antennas over the last few decades [34], [35] and the CP is the more complex type of polarization than linear polarization (LP). The disadvantages of traditional methods of comparison, in which the antennas are practically compared according to only one characteristic, are indicated. Several criteria, simultaneously taking into account the effect of the frequency bandwidth, gain, and antenna dimensions, are proposed. These criteria can be used for a more complete evaluation of antenna characteristics.

3D-Printed Inhomogeneous Dielectric Lens Antenna Diagnostics: A Tool for Assessing Lenses Misprinted Due to Fabrication Tolerances

Abstract: It is difficult to manufacture 3D-printed voxelized inhomogeneous lens antennas exactly to specifications due to fabrication tolerances. Here, we define fabrication tolerances as the sum total of voxelization errors plus printing errors. In this article, we show that the aperture phase is a sensitive function of these fabrication tolerances. A conservative estimate of p0.127-mm error in the amount of material specified to be printed leads to a 1.63d phase error per cell. This error accumulates, as a voxelized lens is generally made of many cells. We present a novel method for diagnosing misprinted lenses and reverse engineering the true permittivity inhomogeneity profile of a lens fabricated within specified tolerances. The technique is based on an inverse-scattering tool that uses geometrical optics (GO) and particleswarm optimization (PSO). Once the actual permittivity profile is found with our method, a new optimal focal point can be calculated by using the same GO-PSO optimization tool to determine where to best feed the misprinted lens. Both numerical and measured examples are given to validate the process. The measured results show that at the new optimal focal point, the measured directivity has been restored to that of the original design specifications.

A Novel Coplanar Antenna Butterfly Structure for Portable Communication Devices: A Compact Antenna With Multioperating Bands

Abstract: This article presents a novel antenna design that consists of a butterfly-shaped radiator, the ground, and the slot between them. A lumped element of resistance was inserted between the ground and the radiator plates to enhance the impedance bandwidth of the antenna. The value of the lumped element and the feeding position was carefully selected to achieve the triple-wide operating bands. The lower operating band (0.75-3 GHz) can support radio-frequency identification (RFID), 3G, GPS, wireless local area network (WLAN) (IEEE 802.11b and IEEE 802.11g), WiMax (IEEE 802.16a), and industrial, scientific and medical (ISM) communications. The second band (4.7-5.95 GHz) is suitable for WLAN (IEEE 802.11a), WiMax (IEEE 802.16d), ISM, and 5G applications, whereas the upper band (7.9-8.6 GHz) can support satellite communications (C-band). The compact size of the antenna (20 x 20 x 0.8 mm3), low profile, acceptable values of gain and efficiency, and omnidirectional pattern in the H-plane make the butterfly antenna suitable for many portable communication devices.

Rye Canyon Radar Cross-Section Measurements of Benchmark Almond Targets [EM Programmer's Notebook]

Abstract: A measurement campaign was conducted at a compact radar range to provide radar cross-section (RCS) data that can serve as a reference for validation, verification, and benchmarking of computational electromagnetics methods. The facility, measurement setup, target construction, measuring instruments, data acquisition, and postprocessing steps are detailed, and sources of measurement uncertainty are identified. To quantify this uncertainty and increase confidence in the measured data, two sets of measurement results using scaled targets are compared to each other and to computational results.

Electromagnetism in the Electrical Engineering Classroom: Dominant trends in teaching classical electromagnetic field theory and innovation vectors

Abstract: This article explores some dominant trends in teaching classical electromagnetic (EM) field theory in electrical engineering (EE) undergraduate curricula. The acronym EM will be used interchangeably to designate either electromagnetic or electromagnetism. The intended significance will be evident from the context.