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A unique micro-metamaterial antenna for light and microwave wavelength conversion is proposed, where the antenna has the form of a panda ring which consists of the mu negative metamaterial silver bars embedded at the microring center. The micro-metamaterial antenna characteristics are investigated, where the antenna resonance frequency and frequency range of 1.60 THz and 1–2.2 THz are achieved. The radiation pattern of the micro-metamaterial antenna is plotted, where the obtained gain and directivity of the antenna are − 8.13 dB. The optimum antenna radiation efficiency is 1 when the antenna has dissipative loss is neglected. The micro-metamaterial antenna can be used as a converter between light and microwave, which is useful for a wavelength converter device.

The scattered fields of antennas can be decomposed into two terms; one depends only on the structure of the antenna while the other depends on the antenna radiation parameters and the loading conditions. This decomposition is used to investigate the antenna radar cross section (RCS) behavior with variable loadings. Then, a general analytical load condition for zero or minimum bistastic radar cross section is derived. The derived formula is used to obtain the regions of feasible passive loads for zero backscattering for three different antenna structures. The backscattering levels of these antennas are examined to validate this formula. The results demonstrate the validity of the procedure with almost zero backscattering for all structures with evident RCS reduction factors.

This paper proposes a simple and efficient technique to improve the antenna radiation performance in stacked printed circuit boards (PCBs) for Internet-of-Things (IoT) applications. In the ...

Implantable antennas are mandatory to transfer data from implants to the external world wirelessly. Smart implants can be used to monitor and diagnose the medical conditions of the patient. The dispersion of the dielectric constant of the tissues and variability of organ structures of the human body absorb most of the antenna radiation. Consequently, implanting an antenna inside the human body is a very challenging task. The design of the antenna is required to fulfill several conditions, such as miniaturization of the antenna dimension, biocompatibility, the satisfaction of the Specific Absorption Rate (SAR), and efficient radiation characteristics. The asymmetric hostile human body environment makes implant antenna technology even more challenging. This paper aims to summarize the recent implantable antenna technologies for medical applications and highlight the major research challenges. Also, it highlights the required technology and the frequency band, and the factors that can affect the radio frequency propagation through human body tissue. It includes a demonstration of a parametric literature investigation of the implantable antennas developed. Furthermore, fabrication and implantation methods of the antenna inside the human body are summarized elaborately. This extensive summary of the medical implantable antenna technology will help in understanding the prospects and challenges of this technology.

The forward and the inverse problem of a thin, circular, loop antenna that radiates in free space is modeled and solved by using soft computing techniques such as artificial neural networks and adaptive neuro fuzzy inference systems. On the one hand, the loop radius and the observation angle serve as inputs to the forward model, whereas the radiation intensity is the output. On the other hand, the electric field intensity and the loop radius are the input and output, respectively, to the inverse model. Extensive numerical tests indicate that the results predicted by the proposed models are in excellent agreement with theoretical data obtained from the existing analytical solutions of the forward problem. Thus, the employment of artificial intelligence techniques for tackling electromagnetic problems turns out to be promising, especially regarding the inverse problems that lack solution with other methods.

The results of the research and development of the unified radiotechnical characteristic of aircraft radomes are presented: an increase in the level of antenna side radiation, associated with the presence of a radome in front of the antenna. It is shown that for an objective assessment of the radio engineering quality of radomes the integral characteristic is best suited – the average increase in the level of antenna radiation power in the required sectors of viewing angles. It has been demonstrated that this characteristic weakly depends on the properties of the antenna with which the radome is estimated.

In this paper, a multi-band antenna composed of irregular metal plate, input feeders and symmetrical defect ground is designed. The antenna radiation enhancement is improved by placing a rectangular artificial magnetic conductor array with zero phase reflection points corresponding to the multi-band antenna frequencies at a fixed distance below. The three impedance bandwidths of the antenna are 2.13-2.58GHz, 3.43-3.64GHz and 5.7-6.0GHz respectively, which effectively cover the 2.4/5.8GHz WLAN band and 2.5/3.5/3.8GHz WIMAX band. By adding AMC reflector, the performance of the antenna in the working frequency band is significantly improved, and a new frequency band is generated at 7.54-8.63 GHz.

An analytical method is proposed for determining the radiation resistance of a linear metal radiator. The method is based on using of the Poynting vector. The obtained results are compared with the results of solving the integral equation for a current in an antenna. The method is generalized to the case of radiators with nonzero boundary conditions. Calculation results are given.

In this paper, the scattered near-fields from electrically large complex PEC objects illuminated by far-field antenna sources are calculated by shooting and bouncing ray (SBR) method. In order obtain accurate near-field scattering results, an physical-optics (PO) near-field integral representation is proposed and reduced to closed form expressions to improve computing efficiency by applying locally expanded Green function approximations. By introducing the proposed PO near-field integral expressions, SBR can be used to analyze near-field scattering from a PEC target under far-field antenna sources radiation. The method is applicable to analyze the near-field scattering problem under arbitrary far-field source incident. Numerical example is presented to demonstrate the efficiency and accuracy of the proposed method.

We propose an optimized approach for implementing Non-Uniform Fast Fourier Transform (NUFFT) algorithms under a general and new perspective for two-dimensional transformations. A case study of electromagnetic interest is carried out by applying the developed NUFFT to the radiation of a planar irregular array antenna onto a set of regular spectral points.

International audience; Antenna characterization using reverberation chamber (RC) has become the new trend in RC measurements. In this work, we compare three antenna characterization methods in RC. These methods are applied in order to determine the radiation efficiency of a patch and a log-periodic antenna. Results are compared and show good coherence. The accuracy of the applied methods is discussed and a solution is proposed in order to enhance the accuracy of reference antenna based methods.

In this Letter, a new polarising grid for a folded reflectarray is proposed to improve the aperture efficiency of the antenna. This polarising grid is designed using a partial grid and a director which can improve the antenna radiation characteristic. Consequently, the measured aperture efficiency of the proposed antenna with the new polarising grid is 60.49% at 77 GHz.

A high-gain ridge gap array antenna, consists of an array of 2×8 monopole antennas with inter-element spacing equals to a wavelength, is proposed and investigated as a promising state-of-the-art grating lobe suppressed high-gain array for millimeter-wave frequency-bands. Increasing the inter-element spacing is a technique for enhancing the directivity; however, it would bring the grating lobe into the visible zone and deteriorate the antenna radiation efficiency. The proposed technique using a supplementary sub-array would suppress the grating lobe in the visible zone. On the other hand, the feeding network is designed with ridge gap waveguide technology in which the waveguide width is about a wavelength making the design of an array antenna with lower inter-element spacing more challenging.

The radiation efficiency prediction using the Wheeler cap is introduced using a semianalytic approach based on the adaptive fitting quality factor method. The procedure details, highlighting the benefits of using the proposed method, are presented, especially in the presence of cavity modes. Also, a procedure is proposed to eliminate the effect of cavity modes for low-frequency antenna measurements. Several studies over the suitability of the proposed procedure are presented to justify the usage of the quality-factor-based method beyond its previous limited usages. The reproduction of results is ensured by considering sufficient data based on an asymptotic prediction of the cavity modes’ frequency spacing. Moreover, full-wave simulation results are presented to verify the proposed method and its immunity to the effects of arbitrary Wheeler caps’ cavity modes in a controlled environment, anticipating possible sources of errors. Also, the same simulated responses are used through other circuit model-independent radiation efficiency prediction procedures to evaluate the performance of the proposed method. Furthermore, the measurement results are presented for various antennas to verify the proposed method in comparison with the full-wave analysis.

In this letter, we show that a cylindrical, single-layer impedance metasurface enclosing a radiating source is capable of reshaping the electromagnetic field pattern at a predetermined radius outside of the metasurface. We first present the design procedure of a cylindrical impedance metasurface and then proceed to an example demonstrating the achievable pattern accuracy. Simulation results validate the design methodology and show that complete amplitude control can be achieved in the azimuthal direction for a vertically polarized source.

Metamaterial (MTM) anomaly dispersion characteristics have a great interest to be analyzed in the potential for increasing antenna performance. Dispersion material with a simple structure is able to cover the weaknesses of the antenna parameters. Characterization and optimization need to be applied to the MTM antenna design to obtain more effective antenna performance. Antenna operation is performed at 0-9 GHz microwave frequency with four SRR-H MTM structures varying in three radii of 2.5 mm, 2.7 mm, and 2.9 mm. The highest MTM characteristics occurred at four SRR-H radii of 2.9 mm with a refractive index of -8.5 which resulted in antenna parameters RL -48.8 dB, 5.98 dBi, and working frequency of 1.09-9.00 GHz. Antenna radiation occurs precisely in all MTM structures with an isotropic pattern or in all directions of 4.63 dBi at a frequency of 5.976 GHz.

In this paper, the effect of integrating complementary split rings into a patch antenna working on the human body is investigated. Different shapes of complementary split rings are integrated into a typical rectangular microstrip patch antenna of (38×46.6×1.6) mm3 in size. The performance of the antenna on a simplified skin model at 2.45 GHz with and without the rings is compared. The simulation results indicate that the antenna radiation efficiency and gain are decreased by up to around 10.14 dB and 9.75 dBi, respectively for the antenna investigated in this paper when the investigated complementary split rings are integrated into its patch. The results in the paper show that unlike the case of complementary split rings with antennas in the human body, the antenna radiation efficiency and gain are decreased when these rings are used with antennas on the human body. The results in this paper are important to distinguish between the performance of complementary split rings with on-body antennas and that of the rings with in-body antennas. They are also important to provide designers with guidelines about using complementary split rings for on body or wearable antennas in general.

Hyperthermia has been introduced as a therapeutic method and adjuvant therapy in the treatment of some diseases such as breast and pancreatic cancers. On the other hand, other applications of hyperthermia have been considered. In this article, ways to treat knee pain caused by osteoarthritis, patellar chondromasia, rheumatism, knee infection, etc., have been studied using antenna hyperthermia. For antenna hyperthermia, is using a rectangular microstrip antenna, which is the simplest type of antenna. The antenna considered in this article has conformal conditions and is designed in the shape of a knee structure, to create a suitable knee covering. The antenna considered in this article has conformal conditions and is designed in the shape of a knee structure, to create a suitable knee covering. In addition to the geometric structure of the antenna, which fits the structure of the knee, the resonance frequency of the antenna is in the range of ISM standard frequencies and attempts have been made to place it at 2.4 GHz. On the other hand, to show the thermal pattern created by the antenna, the specific absorption rate of the tissue is investigated and its diagram is simulated by the antenna radiation field.

The electrical characteristics of the TACAMO antenna are closely related to its flight attitude, which in turn is closely linked to the movement of the aircraft platform. This paper combines its flight attitude simulation and numerical algorithm of electrical characteristics, calculates the electrical parameters of the antenna under specific flight parameters, and then briefly analyzes the relationship between the aircraft movement and antenna radiation characteristics, providing a certain degree of follow-up for this type antenna design and development.

Submarines can navigate underwater and widely used in national defense construction, underwater geological exploration and rescue operations. However, how to achieve effective communication with the submarine has become an urgent problem. According to the development of very low frequency (VLF) communication needs, the electromagnetic theory model of airborne VLF dual trailing antenna system is established. VLF dual trailing antenna radiation characteristics and simulation analysis of near-field characteristics of airborne platform are realized.

This paper presents a compact and highly-efficient inverted-F antenna (IFA) suitable for Internet of Things (IoT) applications. A slotted ground is applied to significantly improve the antenna radiation efficiency. Compared to a conventional IFA on a solid ground plane, the proposed structure enhances radiation efficiency approximately 100%, from 14% to 27%, at 750 MHz. Simulated and measured results are in an excellent agreement, fully validating the IFA response.

In this paper, a novel design of Vivaldi antenna worked in the C, X band with lower RCS has been given. Through the perforation of the antenna metal surface and the dielectric plate, the induced current caused by the incident wave can be bounded with these conductive vias. On the condition that the antenna radiation performance is basically the same circumstances, the RCS of the antenna in the working band can be reduced significantly, especially in the higher frequency part of the operation band.

With the development of nano-optic technology, the optical nano-antenna has been widely used in the flelds of novel light sources, high-sensitive biological sensors, nanometer lithography, and nano-optical imaging. The relationship between the structural parameters of the antenna and the Purcell factor is very important for engineering applications. The electric near fleld proflle of the antenna was calculated and analyzed by using the flnite-difierence time-domain (FDTD) method, and the in∞uence of the structural parameters on the Purcell factor and the electric fleld was thoroughly investigated. A careful comparison of bowtie antenna radiation characteristics with difierent structural parameters was carried out. The results show that the thickness, the length and the curvature radius have great efiects on the Purcell factor and the optical antenna's electric near fleld. These flndings are promising for improving the performance of the optical bowtie nano-antenna.

Recently, a fundamental limit for antenna radiation efficiency was proposed in [1] . Although valid for most antenna applications, a clarification is needed with regard to the fundamental limit expressed by [1 eqs. (14) and (15)] . This clarification is to draw the attention if one like to extend (14) and (15) to cylinders with radius in the range of skin depth. However, it does not invalidate the original work since the skin depth was assumed to be much smaller than the thickness of the object. This point was initially raised by J. Cahill from Technology Service Corporation.

We investigate here the capabilities of a 400-element reconfigurable transmitarray antenna to synthesize monopulse radiation patterns for radar applications in $X$ -band. The generation of the sum ( $\Sigma )$ and difference ( $\Delta $ ) patterns are demonstrated both theoretically and experimentally for broadside as well as tilted beams in different azimuthal planes. Two different feed configurations have been considered, namely, a single focal source and a four-element focal source configuration. The latter enables the simultaneous generation of a $\Sigma $ - and two $\Delta $ -patterns in orthogonal planes, which is an important advantage for tracking applications with stringent requirements in speed and accuracy.

Luneburg lens antenna radiation fields are calculated with Green's functions of spherical and cylindrical layered structures. Electric field components of spherical and cylindrical Luneburg lenses excited by linear and circular polarized incident field are analysed. Dipole, slot and aperture antennas are described by electric and magnetic extraneous currents. Radiation patterns of cylindrical and spherical Luneburg lens are analysed. Co-polarized and cross-polarized field radiation patterns are shown. The proposed method significantly reduces the computing time for multi-layered lenses in comparison with the most commonly used in antenna design. The first step antenna structure optimization may be performed for a shorter time. The results may be used as the first approximation for Ansys HFSS and other software.

We consider an optical antenna that is a linear cluster of nanoparticles inside a metal film on a substrate. Based on discrete sources method has been developed and implemented a mathematical model of the optical antenna. Numerical results demonstrate the ability to control the width of the lobe, and directionality of the antenna radiation.

Most applications of electromagnetic band gap (EBG) concern antenna radiation or electromagnetic filters. In this paper, a metallic EBG structure is designed for stealth applications. We show how this structure allows us to reduce the radar cross section (RCS) of targets. An application of this kind of MEBG is the design of a radome allowing the reduction of antenna RCS. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 546–550, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20693

The performance of wireless power transfer (WPT) systems depends on antenna radiation efficiency and operating resonant frequency. In HF WPT systems, nearby objects have a certain impact on antenna characteristics and consequently on the WPT system performance. In this paper, human-WPT system interaction is investigated in order to provide basic recommendations regarding WPT system design and the human exposure to WPT systems. Preliminary results show that an efficient WPT system with four-arm SHAs is less susceptible to the degradation of system performance due to the influence of the nearby fantom, in comparison with the inefficient WPT between spirals. Also, it is possible to achieve a smaller risk of the electromagnetic human exposure to WPT systems when using an efficient WPT system rather than an inefficient one or a standalone transmitter.

In coplanar waveguide (CPW) circuits, printed balanced antennas must be excited through baluns. These baluns often feature coplanar-to-slotline transitions that must be tuned and matched by electromagnetic optimisation, and may interfere with the antenna backward radiation. A new CPW balun for printed balanced antennas is presented and modelled. As its multimodal circuit model makes clear, it integrates an impedance-matching network within its structure that can be analytically designed. The balun has been experimentally tested, exhibiting good agreement with its circuit model and a weak electromagnetic interaction with the antenna radiation.

The evaluation of antenna radiation features requires the accurate determination of its far-field pattern, whose direct measurement imposes to probe the field at a distance proportionally related to the ratio between the squared dimension D of the antenna aperture and the excitation wavelength (Fig.1). As a consequence of this, the direct evaluation of antenna far-field pattern could require prohibitive distances in the presence of electrically large radiating systems, with increasing complexity and cost of the measurement setup in order to minimize interfering effects.

In this review the author traces the history of antennas and some of the most basic radiating elements, demonstrates the fundamental principles of antenna radiation, reviews Maxwell's equations and electromagnetic boundary conditions, and outlines basic procedures and equations of radiation. Modeling of antenna source excitation is illustrated, and antenna parameters and figures-of-merit are reviewed. Theorems, arraying principles, and advanced asymptotic methods for antenna analysis and design are summarized. >

Oblique Fibonacci samplings provide a methodology to improve the accuracy of numerical calculations for various antenna performance parameters since they are not parallel to the radiation pattern similarities. Conclusions drawn from the periodic array example illustrate how this method can reduce the amount of time required to evaluate far field radiation characteristics of antennas.

A Yagi-type antenna is presented for the shaped radiation pattern synthesis, which will become very useful in the applications of wireless communications. The shaped pattern is formed by properly allocating the directors to weight the directivities in a various directions since the uses of directors have been shown to increase the directivity of a Yagi antenna radiation. Both numerical and experimental examinations have validated the current approach to be very effective in both applications and cost.

An internal printed antenna occupying a small size and covering all the operating bands of WLAN/WiMAX systems for laptop computer applications has been proposed and tested. The antenna is easy to fabricate on a thin FR4 substrate at low cost and shows a size of 9 × 13 mm2 only (not including the system groundplane dimensions), which is about the smallest among the related antennas in the published papers for covering WLAN and WiMAX operations in the wireless devices. The small size for the desired multiband operation is achieved owing to the use of the coupling feed and an embedded band-notching slit in the radiating arm of the proposed PIFA. Good radiation characteristics for frequencies over the operating bands have also been obtained. With the obtained results, the proposed PIFA is very promising for practical WLAN/WiMAX operations in the wireless devices, especially for the thin-profile laptop computers.

A system generating 1.8GHz electromagnetic fields for bio-medical and behavioral study on laboratory animals was designed and implemented. The system is based on a reverberation chamber. An input power up to 5W can be sent to an indoor transmitting antenna and an electric field strength (E) more than 90V/m can be reached inside the chamber. The system was characterized at different input powers measuring E in different points by means of a miniature sensor. Then, boxes with 300cc of physiological liquid inside were realized as simple phantoms simulating laboratory animals (rats) and E inside the liquid was measured, performing several simulations by moving the phantoms (1,2) in the chamber and/or putting them still in different positions. On the basis of these measurements, the SAR (Specific Absorption Rate) and the Pe (power efficiency = SAR/input power) were determined at different powers. The actual system is characterized by a low power efficiency with respect to the "in vivo" exposition systems based on transversal electromagnetic (TEM) cells. Its advantage is to have inside the chamber a habitat similar to the usual one for the laboratory animals.

In this paper, the EMI for AiP is studied. The simulated results indicate the package will influence the performance of antenna, especially, when the ground for antenna, package and system is connected and feed from system board. At the same time, the radiation of antenna will induced the EF in packaged components and bonding trace and the MS line with different load has different response. In order to lessen the effect to packaged component from antenna, the guarding ring and vias fence are used, and the simulated results verify its validity.

This paper deals with the radiation produced by ultra wide band (UWB) impulse radio transmitters. A numerical procedure is proposed in order to define the ideal UWB pulse able to be compliant with the FCC emission mask taking into account the effect of the radiating antenna (antenna factor, radiation pattern). The obtained ideal UWB pulse is then decomposed in a linear combination of Gaussian pulses. Finally, a numerical procedure for electromagnetic field calculation is applied to verify the compliance of the generated pulse with the emission standards

This paper deals with using Reverberation Chamber to obtain antenna radiation efficiency. Reverberation Chambers methods which has for many years been used for EMC (Electromagnetic Compatibility) measurements, can be also used with great advantage for antenna measurements since it simulates effectively a uniform multi-path propagation environment. This paper describes how a Reverberation Chamber can be used to measure the ultra-wideband (UWB) antenna efficiency with very short time. The procedure based on time domain is described and some experimental results are given and compared to the Wheeler Cap method extended by Schantz to UWB antennas. (5 pages)

The plane-wave transmitting spectrum of the system consisting of the ground penetrating radar (GPR) antenna and the air-soil interface is measured using a loop buried in the soil. The plane-wave spectrum is used to determine various parameters characterizing the radiation of the GPR antenna into the soil. The procedure is tested on a spiral antenna.

A new and simple method is proposed for determining the radiation Q of an antenna using the finite difference time domain (FDTD) method. The numerical results are compared with analytical formulas and good agreement is reported.

With the introduction of the "True" Physical Optics, the source in the far field of the canonical structure was not assumed but instead to use the exact dielectric slab's GF's in orde to obtain a more accurate approximation of the PO currents in both the external and the internal sides of the radome. Indeed the PO approximation, consists only in assuming that, for large radii of curvature of the structure, the currents are locally the same as the ones associated to the canonical planar structure that best fits the actual geometry in the point considered.

In this paper we present the comprehensive dispersion characteristics of the slotline on thin and low permittivity substrate with a wide slotwidth comprising the bound and space leaky waves with even and odd electric field symmetry. The final design and measurement of the slotline antenna radiation are based on our analysis of this slotline. The antenna and its feeding circuit are designed assuming only the first odd space leaky wave radiation. Measured and calculated return losses and radiation patterns of the antenna are shown. Remarks are made on the applicability of the antenna.

Electromagnetic scattering and radiation from a circumferential aperture on a shorted coaxial line (dielectric-filled edge-slot antenna, DFES antenna) wa considered in [2]. In this section we will revisit the problem of DFES antenna radiation.

Except for the most trivial cases, antenna radiation problems involving inhomogeneous media escape analytical solution. For these problems, it is necessary to seek computer solutions. To this end, we have investigated Mei's [1] "unimoment" technique as it applies to a biconical antenna immersed in an inhomogeneons medium. The technique is used in conjunction with finite difference methods to analyze some dielectric loading schemes with the goal of improving performance of the biconical antenna. The technique is shown to be sufficiently general to allow analysis of any rotationally symmetric antenna inside an inhomogeneous medium by using more flexible finite element methods. Results of experimental investigations bear out the validity of the technique.