In this paper, we introduce a novel design for a high‐directivity Electromagnetic Band Gap (EBG) resonator antenna that utilizes a frequency‐selective surface (FSS) superstrate. The above type of superstrate is proposed as an alternative to an EBG type of dielectric superstrate—investigated previously by the authors—to reduce its height and facilitate the fabrication process. Although FSS superstrate and the patch antenna comprise a composite resonator, we begin by investigating the FSS structure characteristics first before dealing with the combination. We vary several important parameters, such as the distance between the FSS superstrate and the ground plane of the antenna, and the dimensions of the FSS superstrate, to determine their effect on the resonant frequency and the quality factor of the unit cell of the FSS. The above study enables us to derive some guidelines for an optimum array size of the FSS superstrate that eventually leads to a maximum directivity for the FSS antenna composite, as evidenced via a comparison of the quality factors of the FSS, the unit cell, and the composite. It is demonstrated that the directivity of the antenna with an optimized array size of the FSS superstrate increases by 17.29 to 24.92 dBi for three different strip‐dipole lengths, as compared to that of the patch antenna alone (maximum 6 dBi). © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 462–467, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20502

ABSTRACT:In this letter, a ring-shaped frequency selective surface (FSS)

A NF-FF transformation method applied to antenna far-field characterization using EMC densities to represent the radiation of the source and MGAs for a global optimization technique has been presented in this work as a useful alternative to the most widely used classical methods. The MGA-based approach has been proven to reconstruct accurately the far-field radiation pattern of several sources independently of the near-field samples' arrangement, as can be deduced from the far-field results shown in the document, and from many other simulations carried out by the authors for different radiating sources and equivalent models.The main advantage of this novel approach is that it is more versatile than the classical FFT-based one regarding the sampling geometry. However, it is outperformed by the classical FFT-based method in terms of computational cost. This is the main drawback of the novel approach presented in this work, as its usefulness has been demonstrated when modeling medium-size antennas. Large antennas need more complex equivalent models and the increase in the number of current patches or unknowns slows down the optimization process. ACKNOWLEDGMENTThis work was supported by grant AP2001-1325 of the Spanish State Department of Education and Universities. Technol Conf Budapest, 1993, pp. 191-196 In recent years, electromagnetic bandgap (EBG) materials have attracted much attention among many researchers in the microwave area. Also known as photonic bandgap (PBG) structures that originated in optics [1], they are now finding a wide variety of applications in microwave and millimeter devices, as well as in antennas. In general, EBG materials are periodic arrays consisting of metallic or dielectric elements, which exhibit both stop-(bandgap) and pass-bands. There are two important attributes of EBG materials which can be used for these applications. The first one is to block the propagation of the electromagnetic (EM) fields within a bandgap; this property makes them useful for applications such as waveguides, spatial filters, and antenna substrates. The second important property of EBG materials is that they display localized frequency windows within the forbidden frequency band (bandgap) when the periodicity is broken due to the presence of defects. The frequencies where this occurs are referred to as the defect frequencies, because the above frequency window appears when irregular components are inserted into the periodic structures. This property is very useful for improving the directivity of an antenna when an EBG structure is used as a superstrate for the antenna, which is illuminated by fields radiated from the antenna below. At the defect frequency, the superstrate alters the distribution of the EM fields along specific directions, and also serves to increase the aperture to one much larger than that of the original antenna, thus enhancing the directivity of the antenna in the process. In a previous work, Thevenot et al. used the defect mode generated by a metallic plate, which served as the groun...

No abstract

No abstract

No abstract

Abstract-Magnetic resonance coupling is a widely used technique for wireless power transfer (WPT) in biomedical and consumer electronics applications. For specific applications, device size limits the overall size of the transmit and receive coils. In this work, design considerations for an asymmetrical 4-element WPT system are investigated. For either a target efficiency or a desired WPT range, the optimal coil parameters such as Q and coupling coefficient are defined and these design considerations are experimentally verified. The results can be used to design an optimal set of coils for various WPT applications.

No abstract