Showing papers in "IEEE Antennas and Propagation Magazine in 2009"
TL;DR: This article presents four link budgets that account for the major propagation mechanisms of the backscatter channel, along with a detailed discussion of each.
Abstract: Backscatter radio - wireless communication by modulating signals scattered from a transponder (RF tag) - is fundamentally different from conventional radio because it involves two distinct links: the power-up link for powering passive RF tags, and the backscatter link for describing backscatter communication. Because of severe power constraints on the RF tag, a thorough knowledge of the backscatter channel is necessary to maximize backscatter-radio and radio-frequency identification (RFID) system performance. This article presents four link budgets that account for the major propagation mechanisms of the backscatter channel, along with a detailed discussion of each. Use of the link budgets is demonstrated by a practical UHF RFID portal example. The benefits of future 5.8 GHz multi-antenna backscatter-radio systems are shown. An intuitive analogy for understanding the antenna polarization of RF tag systems is presented.
468 citations
TL;DR: The first-ever two-dimensional sensor integration with an RFID tag module on paper, as well as the possibility of a three-dimensional multilayer paper-based RF/microwave structure, are shown.
Abstract: In this paper, a review of the authors' work on inkjet-printed flexible antennas, fabricated on paper substrates, is given. This is presented as a system-level solution for ultra-low-cost mass production of UHF radio-frequency identification (RFID) tags and wireless sensor nodes (WSN), in an approach that could be easily extended to other microwave and wireless applications. First, we discuss the benefits of using paper as a substrate for high-frequency applications, reporting its very good electrical/dielectric performance up to at least 1 GHz. The RF characteristics of the paper-based substrate are studied by using a microstrip-ring resonator, in order to characterize the dielectric properties (dielectric constant and loss tangent). We then give details about the inkjet-printing technology, including the characterization of the conductive ink, which consists of nano-silver particles. We highlight the importance of this technology as a fast and simple fabrication technique, especially on flexible organic (e.g., LCP) or paper-based substrates. A compact inkjet-printed UHF ldquopassive RFIDrdquo antenna, using the classic T-match approach and designed to match the IC's complex impedance, is presented as a demonstration prototype for this technology. In addition, we briefly touch upon the state-of-the-art area of fully-integrated wireless sensor modules on paper. We show the first-ever two-dimensional sensor integration with an RFID tag module on paper, as well as the possibility of a three-dimensional multilayer paper-based RF/microwave structure.
331 citations
TL;DR: An overview of antenna technologies for applications in modern small satellites is given and specific antennas developed for modern small-satellite applications are explained and discussed.
Abstract: Modern small satellites (MSS) are revolutionizing the space industry. They can drastically reduce the mission cost, and can make access to space more affordable. The relationship between a modern small satellite and a ldquoconventionalrdquo large satellite is similar to that between a modern compact laptop and a ldquoconventionalrdquo work-station computer. This paper gives an overview of antenna technologies for applications in modern small satellites. First, an introduction to modern small satellites and their structures is presented. This is followed by a description of technical challenges in the antenna designs for modern small satellites, and the interactions between the antenna and modern small satellites. Specific antennas developed for modern small-satellite applications are then explained and discussed. The future development and a conclusion are presented.
148 citations
TL;DR: It is concluded that the mutual-coupling problems of transmitting and receiving arrays are in general different, and hence different mutual impedances should be used for mutual-Coupling analysis and compensation.
Abstract: In antenna arrays, mutual coupling between antenna elements is well known as an undesired effect, which degrades the performance of array signal-processing algorithms. The compensation of such an undesired effect has been a popular research topic throughout the years. Various approaches for mutual-coupling compensation have been developed, and they can easily be found in the open literature. In general, the mutual-coupling problems for a transmitting and receiving array are different, even if the physical geometry of the array remains unchanged. However, it seems that antenna engineers are not well aware of such differences in the analysis of receiving antenna arrays. In this note, the mutual-coupling problems in transmitting and receiving antenna arrays are revisited. The differences between the mutual coupling and mutual impedances for transmitting and receiving antenna arrays are explained. It is concluded that the mutual-coupling problems of transmitting and receiving arrays are in general different, and hence different mutual impedances should be used for mutual-coupling analysis and compensation.
137 citations
TL;DR: The definition of return loss is reviewed, the history of the term is outlined, and some examples of current misuse are given to remind everyone of the correct terminology.
Abstract: As Editor-in-Chief of the Transactions, I have noticed over the past year or so that the occasional incorrect use of the term return loss has now grown into a flood of misuse. Perhaps over 30% of all antenna papers submitted to the Transactions in the past twelve months have used return loss incorrectly. The reason for this is uncertain. To remind everyone of the correct terminology, I review the definition of return loss, briefly outline the history of the term, and give some examples of current misuse.
127 citations
TL;DR: A general parameterization of the three-dimensional reading region is proposed, having introduced all of the accessible system data, such as the emitted power, the reader and tag-over-object radiation patterns, and also the interrogation duty cycle, the scenario features, and the safety regulation constraints.
Abstract: The reading range is one of the most critical performance indicators of radio-frequency identification (RFID) systems. It depends on many physical and geometrical parameters. Typically, in the ultra-high-frequency band (UHF: 860 MHz to 960 MHz), the maximum size of the reading region is estimated by the free-space propagation model. This is based on the Friis formula, even if much more accurate predictions may be accomplished nowadays by time-consuming electromagnetic simulations, accounting for the antennas and the interaction with the nearby environment. This paper proposes a general parameterization of the three-dimensional reading region. This done having introduced all of the accessible system data, such as the emitted power, the reader and tag-over-object radiation patterns, and also the interrogation duty cycle, the scenario features, and the safety regulation constraints. Within this framework, the opportunity and some improvements of the free-space model are analyzed. They are compared with measurements and with more-accurate three-dimensional simulations of realistic environments. The discussion demonstrates the validity range of the free-space approximations, and evaluates the improvement achieved by including the main interactions with the environment. The derived formulas are ready to use and to be applied for the planning and optimization of reader-tag networks.
94 citations
TL;DR: In this paper, a dual-frequency dual-polarized array antenna for airborne applications is presented, which can provide simultaneous operation at S band (3 GHz) and X band (10 GHz).
Abstract: A new dual-frequency dual-polarized array antenna for airborne applications is presented in this paper. Two planar arrays with thin substrates (R/T Duroid 5880 substrate, with epsivr = 2.2 and a thickness of 0.13 mm) are integrated to provide simultaneous operation at S band (3 GHz) and X band (10 GHz). Each 3 GHz antenna element is a large rectangular ring-resonator antenna, and has a 9.5 dBi gain that is about 3 dB higher than the gain of an ordinary ring antenna. The 10 GHz antenna elements are circular patches. They are combined to form the array with a gain of 18.3 dBi, using a series-fed structure to save the space of the feeding line network. The ultra-thin array can be easily placed on an aircraft's fuselage, due to its lightweight and conformal structure. It will be useful for wireless communication, radar, remote sensing, and surveillance applications.
86 citations
TL;DR: A thorough investigation of the quality of the software tools widely used nowadays in the field of planar-antenna analysis and synthesis and some designing guidelines are provided that also can simplify the initial selection of EM solvers.
Abstract: The goal of this paper is a thorough investigation of the quality of the software tools widely used nowadays in the field of planar-antenna analysis and synthesis. Six simulation tools - five well-known commercial tools and one developed in-house - are compared with each other for four different planar antennas. It is crucial to point out that all possible efforts have been made to guarantee the most optimal use of each of the software packages, to study in detail any discrepancies between the solvers, and to assess the remaining simulation challenges. The study clearly highlights the importance of understanding EM simulation principles and their inherent limitations for antenna designers. Finally, some designing guidelines are provided that also can simplify the initial selection of EM solvers.
86 citations
TL;DR: In this article, the TM-and TE-mode Q formulas are derived, and a simple approximate form for the lowest-order TM mode is presented, which should better match well-designed electrically small antennas.
Abstract: The Chu fundamental limitation on Q for electrically small antennas is well known and widely used. However, Chu did not include energy stored inside the hypothetical enveloping sphere. Exact calculation of total stored energy by Thal gives a new Q, which should better match well-designed electrically small antennas. The TM- and TE-mode Q formulas are derived, and a simple approximate form for the lowest-order TM mode is presented.
80 citations
TL;DR: In this article, the authors examined random sensor arrays from a compressive-sensing perspective and demonstrated that the natural random-array projections manifested by the media Green's function are consistent with the projection-type measurements associated with compressive sensing.
Abstract: Random sensor arrays are examined from a compressive-sensing (CS) perspective. It is demonstrated that the natural random-array projections manifested by the media Green's function are consistent with the projection-type measurements associated with compressive sensing. This linkage allows the use of existing compressive-sensing theory to quantify the performance of random arrays, of interest for array design. The analysis demonstrates that the compressive-sensing theory is applicable to arrays in vacuum as well as in the presence of surrounding media; further, the presence of surrounding media with known properties may be used to improve array performance.
79 citations
TL;DR: A challenging problem with more than 150 million unknowns has been solved, demonstrating that the proposed implementation of the FMM-FFT constitutes a real alternative to the more frequently used multilevel approaches, such as the Multilevel FMM (MLFMA).
Abstract: An efficient parallel implementation of the Fast Multipole Method (FMM) combined with the fast Fourier transform (FFT) is presented in this paper. The good scaling properties of the FMM-FFT, combined with a smart parallelization strategy, has been shown to be very effective when using large parallel supercomputers. A challenging problem with more than 150 million unknowns has been solved, demonstrating that the proposed implementation of the FMM-FFT constitutes a real alternative to the more frequently used multilevel approaches, such as the Multilevel FMM (MLFMA). Even more importantly, we have achieved a high efficiency with 1,024 parallel processors, which indeed constitutes one of the better scalability results ever reached for a rigorous integral-equation electromagnetic solver.
TL;DR: In this article, the authors consider both the ground plane's size and the location of the antenna on the groundplane in terms of how these factors affect the antenna's performance and demonstrate that often, it is the position of antenna and its feeding point, rather than the size of ground plane itself, that primarily determines the antenna impedance, bandwidth, and radiation mode.
Abstract: The performance properties of small, multi-band, device-integrated antennas are significantly affected by the ground-plane structure on which they are mounted. In many cases, the time-varying current on the ground plane is the primary source of radiation that determines both the antenna's impedance and radiation-pattern properties. With device-sized or integrated antennas, it is sometimes presumed that the primary factor affecting or establishing the antenna's performance is the significantly reduced size of the ground plane. Here, we consider both the ground plane's size and the location of the antenna on the ground plane in terms of how these factors affect the antenna's performance. We demonstrate that often, it is the location of the antenna and its feeding point on the ground plane, rather than the size of the ground plane itself, that primarily establishes the antenna's performance in terms of its impedance, bandwidth, and radiation mode. We also show that in many cases, the method used to feed the antenna and how the feed couples to the ground plane can be significant factors in establishing the current distribution on the ground plane, and therefore the antenna's performance. We demonstrate these effects for several single and multi-band antenna designs.
TL;DR: In this article, the authors provide a comprehensive tutorial on the receiving and scattering properties of antennas, in conjunction with circuit calculations and numerical simulations that illustrate the fundamental concepts of how antennas behave as both receivers and scatterers of electromagnetic fields and power.
Abstract: A tutorial discussion on the receiving and scattering properties of antennas is presented. The objective of this work is to provide a comprehensive tutorial overview of the subject, in conjunction with circuit calculations and numerical simulations that illustrate the fundamental concepts of how antennas behave as both receivers and scatterers of electromagnetic fields and power. The paper begins with a discussion of the basic concepts associated with antenna impedance, as these are fundamental to understanding the antenna's receiving and scattering properties, particularly over a wide range of frequencies, where the circuit properties of the antenna differ. The definitions of aperture efficiency, absorption efficiency, and the validity of using either a Thevenin or Norton equivalent circuit to determine both received and total scattered power are discussed. Circuit circulations and numerical simulations, determining both total received and scattered powers, are presented for a number of antennas, including a straight-wide dipole, a circular loop, a reflector-backed dipole, and a Yagi antenna. We show that Thevenin and Norton equivalent circuits have limited validity when used to determine the total power scattered by a basic antenna element such as the dipole and loop. For the general antenna, these equivalent circuit models are not valid for determining the total scattered power.
TL;DR: The physical limitations of antennas are reviewed in general, with particular emphasis on impedance matching as it relates to ultra-wideband (UWB) antennas (high-pass response) and the use of antenna miniaturization techniques to approach these limits is discussed.
Abstract: Fundamental physical limitations restrict an antenna's performance based on its electrical size These fundamental limits are of the utmost importance, since the minimum size needed to achieve a particular figure of merit can be determined from them In this paper, the physical limitations of antennas are reviewed in general, with particular emphasis on impedance matching as it relates to ultra-wideband (UWB) antennas (high-pass response) Additionally, the use of antenna miniaturization techniques to approach these limits is discussed Using a spiral antenna as an example, guidelines are presented for miniaturizing UWB antennas
TL;DR: The iterative Fourier technique for the synthesis of low-sidelobe patterns for linear arrays with uniform element spacing is described, which uses the property that for a linear array with Uniform element spacing, an inverse Fourier transform relationship exists between the array factor and the element excitations.
Abstract: The iterative Fourier technique for the synthesis of low-sidelobe patterns for linear arrays with uniform element spacing is described. The method uses the property that for a linear array with uniform element spacing, an inverse Fourier transform relationship exists between the array factor and the element excitations. This property is used in an iterative way to derive the array element excitations from the prescribed array factor. A brief outline of the iterative Fourier technique for the synthesis of low-sidelobe patterns for linear arrays will be given. The effectiveness of this method for realizing low-sidelobe sum and difference patterns will be demonstrated for linear arrays equipped with 50 and 80 elements. This demonstration of effectiveness also involves the recovery of the original low-sidelobe patterns, as close as possible, in case of element failures. Included is a program listing of this synthesis method, coded in MATLABtrade. With a few minor modifications/additions, the included MATLAB program can also be used for the design of thinned linear arrays having a periodic element spacing. Since the computational part of the included MATLAB program is coded using vector/matrix operations, this program can easily be extended for the synthesis of low-sidelobe patterns of planar arrays with a periodic element spacing, including pattern recovery in the case of defective elements.
TL;DR: The scalar knife-edge diffraction (KED) solution is a workhorse for RF and optics engineers who regularly encounter practical diffraction phenomena as discussed by the authors, but the approximate, polarization-independent KED result is formulated in a way that does not provide direct physical insight.
Abstract: The scalar knife-edge diffraction (KED) solution is a workhorse for RF and optics engineers who regularly encounter practical diffraction phenomena. However, the approximate, polarization-independent KED result is formulated in a way that does not provide direct physical insight. In this article, we demonstrate how the KED formula contains similar underlying physics to other more-rigorous half-screen diffraction solutions, allowing engineers to apply common geometrical theory of diffraction (GTD) formulations for all screen diffraction problems. The underlying geometrical behavior of the scalar KED solution sheds new light on these old problems, revealing why it is so useful for solving real-word problems in radiowave propagation.
TL;DR: In this paper, a review of the most common rain-rate cumulative distribution conversion methods is presented, together with a complementary set of coefficients for regional and global application by performing regression to a measurements database.
Abstract: The conversion of rain-rate cumulative distributions from any integration time, T, to one minute is a viable option whenever local one-minute data (time series or cumulative distribution functions) are not available for microwave system design. This paper reviews some of the most common rain-rate cumulative-distribution conversion methods. For selected models, it provides a complementary set of coefficients for regional and global application by performing regression to a measurements database. The performance of each model is analyzed, together with its adaptability to various climatic regions. Finally, recommendations with regard to the global applicability of models are given.
TL;DR: Experimental results indicate that the coverage of the RFID system with the phased-array antenna is superior to the coverage with a conventional broader-beamwidth microstrip-patch antenna.
Abstract: In this paper, a UHF-band 2 times 2 microstrip phased-array antenna is designed and implemented to extend the coverage of an RFID reader system. The phased-array antenna has four microstrip-patch antennas, three Wilkinson power dividers, and a transmission-line phase shifter. These are printed on a dielectric substrate with a dielectric constant of 4.5. The array has dimensions of 34 cm times 45 cm, operating at a frequency of 867 MHz, as specified in RFID Gen2 protocol European standards. The phased-array antenna has a measured directivity of 12.1 dB, and the main-beam direction can be steered to angles of plusmn 40deg, with a HPBW of 90deg. The phased-array antenna is used as the receiving antenna in a commercial reader system. Experimental results indicate that the coverage of the RFID system with the phased-array antenna is superior to the coverage with a conventional broader-beamwidth microstrip-patch antenna. The proposed system can also be used for a wireless positioning system.
TL;DR: In this article, a metal-backed loop antenna (MBLA) at high frequency (HF) is characterized and applied to a radio-frequency identification (RFID) smart-shelf system.
Abstract: In this paper, a metal-backed loop antenna (MBLA) at high frequency (HF) is characterized and applied to a radio-frequency identification (RFID) smart-shelf system. The antenna is investigated in terms of impedance matching, resonant frequency, magnetic-field intensity/field distribution, quality factor, and detection range. The study shows that the magnetic-field distribution of the metal-backed loop antenna can be effectively controlled by changing the size as well as the separation of the backing metal plate. As a result, the detection range of an RFID system using such an antenna can be controlled. Such a feature offers great promise for the metal-backed loop antenna in applications for RFID smart-shelf systems. For such systems, controlling the coupling zone of the antennas is vital for constraining the interference between the antennas in adjacent tiers of the shelves, in order to achieve high system-detection accuracy. In addition, using a metal-backed loop antenna provides more flexibility for RFID smart-shelf-system design and implementation, so that the system is more cost effective.
TL;DR: In this article, a set of rain-rate contour maps, useful for link and network power sizing in Nigeria, were developed using a combination of first-order rain rate statistical methods: the Moupfouma-Martin model for rain rate prediction in tropical regions, and the Rice-Holmberg model.
Abstract: Rain attenuation is the dominant propagation impairment for high-frequency microwave systems. System design therefore requires the knowledge of the one-minute integrated rain-rate cumulative distribution function over the coverage area in order to determine the appropriate transmitter and receiver characteristics. This paper presents a set of rain-rate contour maps, useful for link and network power sizing in Nigeria. They were developed using a combination of first-order rain-rate statistical methods: the Moupfouma-Martin model for rain-rate prediction in tropical regions, and the Rice-Holmberg model.
TL;DR: The displacement-current concept introduced by James Clerk Maxwell is generally acknowledged as one of the most innovative concepts ever introduced in the development of physical science as mentioned in this paper, and it was through this that he was led to the discovery of his electromagnetic theory of light.
Abstract: The displacement-current concept introduced by James Clerk Maxwell is generally acknowledged as one of the most innovative concepts ever introduced in the development of physical science. It was through this that he was led to the discovery of his electromagnetic theory of light. While this concept and its development have received much admiration in the literature from the viewpoints of both scientific content and philosophical methodology, there interestingly has been criticism, as well. This article presents an overview of these perspectives. With the distinctive creative quality of the concept emerging on balance, it is suggested that effective use of it can be made to help students to contemplate innovation and creativity, among other factors.
TL;DR: It is shown that the MWR, or MoM, is not just a method per se: it can in fact be a general framework for or approach to unifying or deriving most of the numerical methods developed so far, either in the frequency domain or in the time domain.
Abstract: The method of the weighted residuals (MWR), sometimes known as the method of moments (MoM), has traditionally been applied in the frequency domain and has been shown to be effective and efficient, especially in computing open electromagnetic structure problems. Although it has been extended to the time domain in various forms, it is generally employed to solve integral formulations derived from Maxwell's equations. Therefore, it is often considered to be one type of numerical method that is different from other numerical methods, such as finite-difference methods. However, in this paper we will show that the MWR, or MoM, is not just a method per se: it can in fact be a general framework for or approach to unifying or deriving most of the numerical methods developed so far, either in the frequency domain or in the time domain. As a result, all numerical methods can be quite easily understood and can be categorized in one general method, although their conventional derivations may still have their respective advantages. One potential application is that the hybridization of different numerical methods can now be done within a uniform framework. The paper is intended for both beginners and experienced practitioners in the area of numerical electromagnetic modeling.
TL;DR: In this paper, the authors used the truncated-wedge incremental-length diffraction coefficients (TW-ILDC) method to solve three-dimensional (3D) scattering problems in the terahertz (THz) frequency range.
Abstract: Electromagnetic (EM) scattering characteristics of perfectly electrical conducting (PEC) targets in the terahertz (THz) frequency range are investigated through the use of ray-based high-frequency EM techniques. These techniques include the methods of shooting and bouncing rays (SBR), and the truncated-wedge incremental-length diffraction coefficients (TW-ILDCs). The EM fields associated with each ray are tracked and computed, based on the principle of physical optics (PO) and/or geometrical optics (GO). The total field scattered from the PEC target is then obtained by summing up the EM contributions of each ray and each illuminated edge. In contrast to previously reported applications, these methods are combined together to solve three-dimensional (3D) scattering problems in the THz region. Due to the use of analytical formulas of physical optics and the truncated-wedge incremental-length diffraction coefficients method, the consideration of the multi-reflection effect in shooting and bouncing rays, and partially accounting for the second-order edge-diffraction effects in the truncated-wedge incremental-length diffraction coefficients method, we obtain an extremely efficient algorithm for studying THz scattering. It has excellent agreement with an accurate integral solver, the multilevel fast multipole algorithm (MLFMA), which cannot be used in handling large-scale THz problems. Both mono- and bistatic radar cross sections (RCS) of several PEC objects in the THz band are given to show the correctness and reliability of the asymptotic methods. The EM scattering characteristics of such targets in the THz region are analyzed. Great differences of the target characteristics between the THz and GHz regimes are observed and discussed.
Journal Article•
TL;DR: In this paper, a novel setup based on the use of non-invasive dielectric field probes, and employing accurate and reliable algorithms for antenna characterization, is described, and experimental results show how the proposed system can provide even more accurate characterizations than standard near-field systems, enabling considerable reduction of indoor test-range dimensions.
Abstract: A novel setup, based on the use of non-invasive dielectric field probes, and employing accurate and reliable algorithms for antenna characterization, is described. Experimental results show how the proposed system can provide even more accurate characterizations than standard near-field systems, enabling considerable reduction of indoor test-range dimensions (compact near-field) . Also, the potential fo·r very-near-field acquisition, as well as the sampling strategy in the reactive zone of the radiator, are pointed out.
TL;DR: In this paper, a general overview of laptop-antenna integration aspects is given, along with unified guidelines for the design of the wireless interface used in modern laptops, and an application of the novel elements to capacity-preserving MIMO arrays is also presented.
Abstract: The objective of this article is to provide a comprehensive and unified description of the authors' work on the development of wrapped microstrip antennas for laptop applications. The first contribution is the introduction of quasi-omnidirectional wrapped-microstrip antenna elements to be integrated into the display rim of laptops. Single- and dual-band antennas are presented to demonstrate the capabilities of wrapped microstrip antenna elements in wireless communications. The prototyping and measurements of these antennas are highlighted in an appendix. The most common internal and external laptop antenna structures are also described, to give a broader overview of laptop antenna-design approaches. The second and third contributions are a methodical analysis of housing effects, and a general study of electromagnetic human interaction with laptop antennas from the antenna-performance-degradation and user-illumination perspectives. These studies have been performed systematically for several classes of internal and external antennas, with different locations and screen-opening angles. With this approach, a general overview of laptop-antenna integration aspects is given, along with unified guidelines for the design of the wireless interface used in modern laptops. An application of the novel elements to capacity-preserving MIMO arrays is also presented.
TL;DR: A 17 GHz receiving multibeam active phased array, based on modular "suopertiles," was built and tested in this paper, where measured array-antenna patterns were in good agreement with estimated and predicted values, proving that the array can be built according to its requirements, and calibrated and controlled to generate independent beams with low sidelobes from low rms excitation errors.
Abstract: A 17 GHz receiving multibeam active phased array, based on modular "suopertiles," was built and tested. The array was launched and placed in geostationary orbit in 2008. The tile concept is characterized by low volume and low mass, making it well suited for satellite-antenna applications, and in particular for deployed multibeam active phased arrays for communications satellites. The modular design facilitates low recurring cost in a high-volume continuous production. Both component and array measurement data are presented in the paper. Measured array-antenna patterns were in good agreement with estimated and predicted values, proving that the array can be built according to its requirements, and calibrated and controlled to generate independent beams with low sidelobes from low-rms excitation errors.
TL;DR: In this article, a new design procedure is proposed for the design of wideband constant-beamwidth conical corrugated-horn antennas, with minimum design and construction complexity, based on these values, the procedure gives a relatively good design with a relative bandwidth of up to 2.5:1.
Abstract: In this paper, a new design procedure is proposed for the design of wideband constant-beamwidth conical corrugated-horn antennas, with minimum design and construction complexity. The inputs to the procedure are the operating frequency band, the required minimum beamwidth in the entire frequency band, and the frequency in which the maximum gain is desired to occur. Based on these values, the procedure gives a relatively good design with a relative bandwidth of up to 2.5:1. Based on the proposed procedure, a corrugated-horn antenna with a constant beamwidth over the frequencies of 8 to 18 GHz was designed and simulated using commercial software. The designed antenna was also constructed, and its electromagnetic performance was measured. The measured results of the constructed prototype antenna confirmed the simulation results and satisfied the design requirements, validating the proposed design procedure.
TL;DR: In this article, a novel setup based on the use of non-invasive dielectric field probes, and employing accurate and reliable algorithms for antenna characterization, is described, and experimental results show how the proposed system can provide even more accurate characterizations than standard near-field systems, enabling considerable reduction of indoor test-range dimensions.
Abstract: A novel setup, based on the use of non-invasive dielectric field probes, and employing accurate and reliable algorithms for antenna characterization, is described. Experimental results show how the proposed system can provide even more accurate characterizations than standard near-field systems, enabling considerable reduction of indoor test-range dimensions (compact near-field). Also, the potential for very-near-field acquisition, as well as the sampling strategy in the reactive zone of the radiator, are pointed out.
TL;DR: The results of four years of work within the Antenna Software Initiative (ASI) of the European Network of Excellence on Antennas (ACE) are reported, to build a European framework that allows research groups, active in the development of antenna analysis and design software, to intensify and optimize cooperative research.
Abstract: The results of four years of work within the Antenna Software Initiative (ASI) of the European Network of Excellence on Antennas (ACE) are reported. The primary goal of the ASI was to build a European framework that allows research groups, active in the development of antenna analysis and design software, to intensify and optimize cooperative research. The ASI community worked on three concrete questions: what software do we have, how good is it, and how can we make it better? This work was performed in close cooperation with ESA-ESTEC. At the last EuCAP conference (March 2009, Berlin), the EuRAAP Working Group on Software was inaugurated. The goal of this Working Group is to continue the work of the ASI community. It has to be emphasized that the ASI structure is a structure set up in a democratic way, to cope with the most important bottlenecks encountered towards European antenna-software cooperation.
TL;DR: In this paper, the cause and effect of the displacement current were investigated in the most basic of terms, starting from Coulomb's law, and the authors shed new light on some questions that have dogged the concept, and to help understanding of the key issues involved.
Abstract: Maxwell's displacement current is addressed in the most basic of terms, starting from Coulomb's law. The aim of this approach is to shed new light on some questions that have dogged the concept, and to help understanding of the key issues involved, in particular, cause and effect, common origin of induced magnetic field and displacement current, differences resulting from a fundamental physical view as opposed to a purely phenomenological view, and finally the appropriate choice of magnetic source terms.