78 W. ALI, E. HAMAD, M. BASSIUNY, ET AL., CSRR BASED TRIPLE BAND MICROSTRIP ANTENNA FOR WLAN/WiMAX… DOI: 10.13164/re.2017.0078 ELECTROMAGNETICS Complementary Split Ring Resonator Based Triple Band Microstrip Antenna for WLAN/WiMAX Applications Wael ALI 1 , Ehab HAMAD 2 , Mohamed BASSIUNY 3 , Mohamed HAMDALLAH 3 1 Dept. of Electronics & Comm. Engineering, College of Engineering, Arab Academy for Science, Technology and Maritime Transport (AASTMT), Alexandria, Egypt 2 Dept. of Electrical Engineering, Aswan Faculty of Engineering, Aswan University, Aswan 81542, Egypt 3 Dept. of Electronics & Comm. Engineering, College of Engineering, Arab Academy for Science, Technology and Maritime Transport (AASTMT), Aswan, Egypt wael_abd_ellatif@yahoo.com, e.hamad@aswu.edu.eg, atefrana@yahoo.com, eng_zakaria_aast@yahoo.com Submitted August 19, 2016 / Accepted October 30, 2016 Abstract. A new simple design of a triple-band microstrip antenna using metamaterial concept is presented in this paper. Multi-unit cell was the key of the multi resonance response that was obtained by etching two circular and one rectangular split ring resonator (SRR) unit cells in the ground plane of a conventional patch operating at 3.56 GHz. The circular unit cells are resonating at 5.6 GHz for the upper band of Wi-MAX, while the rectan- gular cell is designed to produce a resonance at 2.45 GHz for the lower band of WLAN. WiMAX's/WLAN's operating bands are covered by the triple resonances which are achieved by the proposed antenna with quite enhanced performance. A detailed parametric study of the placement for the metamaterial unit cells is introduced and the most suitable positions are chosen to be the place of the unit cells for enhanced performance. A good consistency be- tween simulation and measurement confirms the ability of the proposed antenna to achieve an improved gain at the three different frequencies. Keywords Metamaterial, metasurface, multi band antennas, CSRR, split ring resonators 1. Introduction Microstrip patch antennas are the preferable type of antennas used for wireless communication systems, be- cause of their attractive features such as light weight, low profile, low cost, easy fabrication, and compatibility with planar monolithic microwave integrated circuit (MMIC) components [1]. Various printed antenna topologies have been proposed by researchers for the purpose of enhancing their performance. One of these topologies can be achieved by changing the geometry of the patch itself or defecting the ground plane of the antenna as proposed in [2], where an antenna for ultra-high frequency application is designed. Multi-circular shape of the patch in [3] was used to provide an enhanced performance of multiband antennas. Also, authors in [4] proposed a dual-band antenna realized by two different single-slotted single-band rectangular micro- strip antennas. Because of their fascinating properties, metamaterials are recently used for many applications in the field of an- tenna design [5]. There are a lot of antennas that have been developed based on metamaterials such as the antennas based on engineered dispersion curves (k–β diagram) [6], and the antennas based on the split-ring resonators (SRRs) and/or complementary split-ring resonators (CSRRs) [7]. Metamaterial antennas provide various techniques that can be used for improving antenna performance such as in [8] where TL-MTM technique is used to generate a multi band response. Metamaterial can also be used for enhancing the antenna parameters such as its bandwidth and gain. In [9], the design of a dual band antenna with an enhanced band- width is presented. In [10], metasurfaces are used to im- prove the gain of the antenna. In some applications, the main required feature for an antenna is its polarization and this parameter can also be controlled by using meta- materials in [11]. In this paper, a compact triple-band microstrip an- tenna based on CSRRs with two different geometries loaded on the ground plane is proposed. A conventional patch antenna operating at 3.6 GHz, which is operating in the middle WiMAX band (3.2 GHz to 3.8 GHz), is loaded on a ground plane with a rectangular CSRR of suitable dimensions that enables the excitation of the lower WLAN band (2.4 GHz to 2.484 GHz). Also, two circular CSRRs of suitable dimensions are loaded on the ground plane in order to resonate at the upper WiMAX frequency bands (5.25 GHz to 5.85 GHz). Finite Element Method (FEM) based software, Ansoft HFSS 13, is used for the analysis of the proposed antenna and optimizing its geometrical pa- rameters. The main advantage of this proposed design over different multiband antenna designs is its accurate determi- nation of all resonance frequencies i.e. every specific reso-