1536-1225 (c) 2019 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information. This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/LAWP.2019.2929579, IEEE Antennas and Wireless Propagation Letters Abstract— A new wideband and enhanced gain Fabry-Pérot cavity antenna is presented in this paper. The Fabry-Pérot cavity is established between a single-layer metamaterial-based partially reflective surface (PRS) and a simple feeding slot antenna. The unit cell of the PRS consists of printed and etched square rings on both sides of the superstrate. A 6x6 array of the unit cells are optimized to produce a positive reflection phase gradient required for the gain enhancement. Simulated results of the designed Ku- band antenna demonstrate an impedance bandwidth of 13.1-15.3 GHz (15.5 %) with a gain enhancement up to 8.2 dB (i.e., 150% gain increase above the feeding antenna) and a 3-dB radiation bandwidth of 18.7%. Experimentally observed reflection and radiation responses of the fabricated prototype validate the simulated results. Index Terms— wideband, Fabry-Pérot antenna, high gain, partially reflective surface (PRS). I. INTRODUCTION ECENT developments in electromagnetic metamaterials have attracted considerable research interest in solving some of the significant challenges in electromagnetics [1]-[5]. The electromagnetic bandgap (EBG) structures as a widely known metamaterial example can be employed to block or guide the propagation of EM energy in specific bands of frequencies [6]-[13]. Additionally, several designs have employed EBG to improve antennas performances [14]-[15]. More specifically, EBG structures have been used as an effective partially reflective surface (PRS). A PRS is a periodic surface constituted by an assembly of similar elements arranged in a 1D or 2D limited array. A PRS demonstrates attractive features when employed as a superstrate of elementary printed antennas. Several radiating structures were implemented utilizing this approach employing a single, dual- or triple-layer superstrate [6]-[9]. Fabry-Pérot cavity (FPC) antennas have drawn substantial attention after the first conductive arrays were employed as a PRS to enhance the antenna gain as described in [16]. Typically, high-gain antennas are achieved by periodically printing a unit cell in a 2D lattice with a reasonably high Manuscript received Feb. 15, 2019; revised May 13, 2019; accepted July 09, 2019. Corresponding author: Hussein Attia (hattia@kfupm.edu.sa). This work was supported by King Fahd University of Petroleum and Minerals (KFUPM) under DSR project number SB181021, and by the Algerian Ministry of Higher Education and Scientific Research (MESRS). reflection coefficient over a simple antenna (i.e., patch, slot, and dipole) that is integrated in a metallic (i.e., ground) plane to establish an FPC structure [12]-[13]. In this work, a wideband and enhanced gain FPC antenna is proposed. The PRS superstrate as shown in Fig. 1 is established by printing complementary square ring patches on its top face and square ring apertures on its bottom face. The proposed FPC antenna fed by an isosceles-triangular slot can be an essential component of satellite communication systems operating in the Ku-band. The total height of the cavity is about a half free-space wavelength. The resonance condition [16] required to significantly enhance the gain of the FPC antenna is to design a PRS with a reflection phase that increases with frequency (i.e., positive phase gradient). This positive gradient of the reflection phase is adjusted to cover the desired frequency range. In contrast to the previous work employing dual- and triple- layer PRS to increase the radiation bandwidth [6]-[10], the presented work utilizes only a single PRS layer. The proposed low-profile FPC antenna, to the best of the authors’ knowledge, outperforms all its competitors in terms of achieving broad radiation and impedance bandwidths combined with a very high percentage gain increase (i.e., 150%) compared with the gain of the feeding slot antenna. This paper is organized as follows. In Section II, the development of the PRS building blocks and the proposed antenna are described. In addition, a parametric study based on CST simulator is presented. Section III presents the measurement results to validate the proposed concept. Finally, the conclusion of this paper is presented in the last Section. II. PRS AND FEEDING ANTENNA DESIGN A. PRS Design The resonance condition necessitated to enhance the gain of an FPC antenna is given as [16] ( ) 2 , 0,1, 2, ...... (1) 4 PRS c f n n etc h     = − + = where ψ PRS is the phase of the reflection coefficient of the PRS, and “h” is the gap height separating the ground plane from the M. A. Meriche and A. Messai are with Electronics Department, University of frères Mentouri, Constantine-1, Algeria. H. Attia and S. I. M. Sheikh are with King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia (email: hattia@kfupm.edu.sa). T. A. Denidni is with EMT-INRS, Montréal (QC) Canada. Directive Wideband Cavity Antenna with Single Layer Meta-Superstrate M. A. Meriche, H. Attia, Member, IEEE, A. Messai, S. I. M. Sheikh, Senior Member, IEEE, and T. A. Denidni, Fellow, IEEE R