Yanfei Li

Bio: Yanfei Li is an academic researcher from Communication University of China. The author has contributed to research in topics: Microstrip antenna & Directivity. The author has an hindex of 4, co-authored 8 publications receiving 55 citations. Previous affiliations of Yanfei Li include Pennsylvania State University.

A comparative study of directivity enhancement of microstrip patch antennas with using three different superstrates

Abstract: In this article, we present the results of a comparative study of three different types of superstrates used to enhance the directivity of a microstrip patch antenna. The three superstrates are frequency selective surface (FSS) with dipole elements; a dielectric slab; and a double negative (DNG) slab. We find that microstrip antennas (MPAs) covered either by an FSS or a plain dielectric slab superstrate provide higher directivities than that realized by using a DNG superstrate. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 327–331, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24898

Directivity enhancement of fabry‐perot antenna by using a stepped‐dielectric slab superstrate

Abstract: A Fabry-Perot resonator excited by a microstrip patch antenna that has a superstrate with a stepped dielectric constant is designed to operate at 5.8 GHz. The antenna is fabricated and is shown to provide enhanced directivity over that achievable using uniform dielectric slabs, with either er = 4.4 or er = 10.2 as superstrates. The measured maximum gain of the patch antenna with a step-index dielectric constant superstrate with a dimension of 2λ0 × 2λ0 was found to be 13.44 dBi, whereas the corresponding values for the uniform dielectric superstrate are 11.25 (er = 4.4) and 12.44 dBi (er = 10.2). As shown in this article, the aperture efficiency of the step-index dielectric is also higher than those of the other two. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:711–715, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26614

Directivity Enhancement of Microstrip Patch Antennas Using a Dieletric Superstrate

Abstract: In this paper, we present a systematic design methodology for enhancing the direc- tivity of microstrip patch antennas (MPAs), by using it as an exciter of a Fabry-Perot (FP) (6) resonant cavity. The design procedure involves three steps: (i) determing the resonance fre- quency of the empty cavity, with the MPA removed, when operating in the receive mode; (ii) designing the patch antenna to operate at the same frequency in the presence of the superstrates; (iii) flnally, we operate the composite system in the transmit mode to investigate its aperture distribution that provides us a clue for enhancing the directivity. We show that the directivity can be enhanced by more than 8dB, over that of the MPA without the superstrate, by using either planar or curved superstrates as covers for the MPA.

Directivity enhancement of microstrip antennas using dielectric superstrates

Abstract: The subject of directivity enhancement of microstrip patch antennas (MPAs), using either a Frequency Selective Surface (FSS) or a double-negative (DNG) metamaterial slab, has been investigated by a number of researchers in recent years. The purpose of this paper is to show that we can also achieve the same goal by using a much simpler design for the superstrate, namely a dielectric slab, whose performance can comparable, and even be superior to those of the other two typical choices for the superstrate, namely the FSS or the DNG.

Design of high performance sleeve dipole array antenna

Abstract: A 5-element planar dipole array antenna is analyzed and successfully implemented. The proposed antenna is designed for operation at 1.9 GHz band for basic station applications with S 11 < −14 dB. The planar dipole array antenna comprises of a 1×5 dipole array and fed by a microstrip line. This structure is easily constructed by printing on both sides of a dielectric (FR4) substrate. The measured −14 dB return loss (VSWR 1.5:1) impedance bandwidth is around 7.0% (1.79–1.92 GHz). A reflector is put behind the dipole array to obtain directional radiation and high gain, and the measured maximum gain for operating frequencies across the 1.9 GHz band is about 6.9–8.6 dBi. The measured results of radiation efficiency, radiation pattern, antenna gain and return loss show that this dipole array is with a good performance.

Steering the Beam of Medium-to-High Gain Antennas Using Near-Field Phase Transformation

Abstract: A method to steer the beam of aperture-type antennas is presented in this paper. Beam steering is achieved by transforming phase of the antenna near field using a pair of totally passive metasurfaces, which are located just above and parallel to the antenna. They are rotated independently or synchronously around the antenna axis. A prototype, with a peak gain of 19.4 dBi, demonstrated experimentally that the beam of a resonant cavity antenna can be steered to any direction within a large conical region (with an apex angle of 102°), with less than 3-dB gain variation, by simply turning the two metasurfaces without moving the antenna at all. Measured gain variation within a 92° cone is only 1.9 dBi. Contrary to conventional mechanical steering methods, such as moving reflector antennas with multiaxis rotary joints, the 3-D volume occupied by this antenna system does not change during beam steering. This advantage, together with its low profile, makes it a strong contender for space-limited applications where beam steering with active devices is not desirable due to cost, nonlinear distortion, limited power handling, sensitivity to temperature variations, radio frequency losses, or associated heating. This beam steering method using near-field phase transformation can also be applied to other aperture-type antennas and arrays with medium-to-high gains.

Dielectric Phase-Correcting Structures for Electromagnetic Band Gap Resonator Antennas

Abstract: A novel technique to design a phase-correcting structure (PCS) for an electromagnetic band gap (EBG) resonator antenna (ERA) is presented. The aperture field of a classical ERA has a significantly nonuniform phase distribution, which adversely affects its radiation characteristics. An all-dielectric PCS was designed to transform such a phase distribution to a nearly uniform phase distribution. A prototype designed using proposed technique was fabricated and tested to verify proposed methodology and to validate predicted results. A very good agreement between the predicted and the measured results is noted. Significant increase in antenna performance has been achieved due to this phase correction, including 9-dB improvement in antenna directivity (from 12.3 dBi to 21.6 dBi), lower side lobes, higher gain, and better aperture efficiency. The phase-corrected antenna has a 3-dB directivity bandwidth of 8%.

Analytical Model for Calculating the Radiation Field of Microstrip Antennas With Artificial Magnetic Superstrates: Theory and Experiment

Abstract: A fast analytical solution for the radiation field of a microstrip antenna loaded with a generalized superstrate is proposed using the cavity model of microstrip antennas in conjunction with the reciprocity theorem and the transmission line analogy. The proposed analytical formulation for the antenna's far-field is much faster when compared to full-wave numerical methods. It only needs 2% of the time acquired by full-wave analysis. Therefore the proposed method can be used for design and optimization purposes. The method is verified using both numerical and experimental results. This verification is done for both conventional dielectric superstrates, and also for artificial superstrates. The analytical formulation introduced here can be extended for the case of a patch antenna embedded in a multilayered artificial dielectric structure. Arguably, the proposed analytical technique is applied for the first time for the case of a practical microstrip patch antenna working in the Universal Mobile Telecommunications System (UMTS) band and covered with a superstrate made of an artificial periodic metamaterial with dispersive permeability and permittivity.

Performance enhancement of patch antenna array for 5.8 GHz Wi-MAX applications using metamaterial inspired technique

Abstract: Though a microstrip patch antenna has advantages of low profile and structural planarity, but a single microstrip patch antenna has limitation of low gain and narrow bandwidth To overcome these problems, multi-layer structures are used The antenna performance can further be enhanced, if multi-layer structures are designed for array of patch antennas Moreover, the simultaneous improvement of gain and bandwidth, which are two conflicting parameters, is another challenge To meet these challenges, this article proposes a microstrip patch antenna array, inspired with a superstrate – comprising of Split Ring Resonators (SRR) and wire strips Gain and bandwidth of 43 dBi and 425 MHz, respectively, is achieved by an unloaded array at IEEE 80216a 58 GHz Wi-MAX band However, by covering this array with the proposed superstrate, gain and bandwidth of 121 dBi and 780 MHz, respectively, is obtained, thus providing the gain improvement of 78 dBi and bandwidth enhancement of 355 MHz Fabrication and testing of the proposed antenna is done for comparing simulated and measured results Equivalent circuit of this newly devised array has been designed and discussed

Study of Antenna Superstrates Using Metamaterials for Directivity Enhancement Based on Fabry-Perot Resonant Cavity

Abstract: Metamaterial superstrate is a significant method to obtain high directivity of one or a few antennas. In this paper, the characteristics of directivity enhancement using different metamaterial structures as antenna superstrates, such as electromagnetic bandgap (EBG) structures, frequency selective surface (FSS), and left-handed material (LHM), are unifiedly studied by applying the theory of Fabry-Perot (F-P) resonant cavity. Focusing on the analysis of reflection phase and magnitude of superstrates in presently proposed designs, the essential reason for high-directivity antenna with different superstrates can be revealed in terms of the F-P resonant theory. Furthermore, a new design of the optimum reflection coefficient of superstrates for the maximum antenna directivity is proposed and validated. The optimum location of the LHM superstrate which is based on a refractive lens model can be determined by the F-P resonant distance.