Regular paper Asymmetric CPW-fed electrically small metamaterial- inspired wideband antenna for 3.3/3.5/5.5 GHz WiMAX and 5.2/5.8 GHz WLAN applications Mohammad Ameen, Abinash Mishra, Raghvendra Kumar Chaudhary ⇑ Department of Electronics Engineering, Indian Institute of Technology (Indian School of Mines), Dhanbad, Jharkhand 826004, India article info Article history: Received 19 November 2019 Accepted 17 March 2020 Keywords: Asymmetric coplanar waveguide (ACPW) Compact antenna Closed ring resonator (CRR) Split-ring resonator (SRR) Wideband antenna abstract In this work, a new concept is introduced to enhance the bandwidth of metamaterial (MTM) inspired antenna. The MTM inspired antenna mainly comprises a single split-ring resonator and a hexagonal- shaped closed ring resonator with asymmetric coplanar waveguide feed, which leads to antenna com- pactness. The physical dimension of the intended antenna is 17 mm  20 mm  1.6 mm. Due to MTM loading, the antenna achieves more compactness with ka = 0.87 < 1 resulting in a smaller electrical dimension of 0.18k 0  0.21k 0  0.017k 0 at 3.24 GHz. The intended antenna provides a wider bandwidth ranges from 3.06 GHz to 5.89 GHz with a percentage impedance bandwidth of 63.24% due to the merging of two resonating modes into a single passband. The proposed antenna provides a gain greater than 2 dBi for the entire working band with a maximal gain of 3.65 dBi at 5.2 GHz and radiation efficiency greater than 85% for the complete working band. Also, the antenna shows a consistent radiation pattern through- out the working band and hence the intended antenna is appropriate for 5.2/5.8 GHz WLAN IEEE 802.11 a/h/j/y, and 3.3/3.5/5.5 GHz WiMAX IEEE 802.16e applications. Ó 2020 Elsevier GmbH. All rights reserved. 1. Introduction Now a days, the quality and reliability of modern wireless com- munication systems are improving, hence it is very essential to have a compact, economic, and low profile antenna with higher radiation efficiency and acceptable gain. The traditional approach employs microstrip patch antennas for antenna compactness, where the resonant length of the radiating element is around half of the guided wavelength. The main demerit of using this approach is the narrow impedance bandwidth (IBW), poor impedance matching, lower radiation efficiency, higher cross-polar radiation, and smaller gain values [1]. To overcome these difficulties, new approaches using metamaterials (MTMs) can be utilized for design compact antennas with better features compared with the classical microstrip based patch antennas [2]. MTMs are artificial electro- magnetic periodic structures having negative permeability (l <0) and permittivity (e <0) concurrently and it shows unusual property like left-handed (LH) propagation of the electromagnetic wave, antiparallel phase velocity and group velocity, negative refractive index, zero propagation constant at zeroth order resonance (ZOR) which is not possible for the existing right- handed materials [2]. MTM based antennas can be realized by using composite right/left-handed (CRLH) transmission line (TL) [3–10], epsilon negative TL [11–13], mu-negative TL [14–15], reso- nant approaches using loading of split-ring resonator (SRR) and complementary split-ring resonator (CSRR) [16–22], and loading of various MTM inspired structures [23–33] for antenna miniatur- ization with improved performance. The TL line approach utilizes CRLH-TL antenna which provides ZOR by employing the series square patch and shunt meander line inductor [3], ZOR antenna utilizing coplanar waveguide (CPW) feed with resonant ring [4], CRLH-TL based wideband antenna [5,6], asym- metric CPW (ACPW) based broadband MTM antenna by combining ZOR and first-order resonance [7,8], ohm-shaped interdigital capaci- tor (IDC) [9], multiple CRLH-TL unit cells with IDC and meander lines [10], ENG-TL antennas are realized by cascading multiple unit cells utilizing meander lines and asymmetric ground plane [11], compact mushroom structures for antenna miniaturization [12], thin conduct- ing layer with bow-tie shaped virtual ground antenna utilizes CPW feed with backed ground plane [13], Mu-negative antennas are implemented the combination of series gap capacitor and shunt floating inductor employing meander lines [14] and two-conductor coplanar strip TL with pairs of asymmetric IDC [15]. https://doi.org/10.1016/j.aeue.2020.153177 1434-8411/Ó 2020 Elsevier GmbH. All rights reserved. ⇑ Corresponding author. E-mail address: raghvendra.chaudhary@gmail.com (R.K. Chaudhary). Int. J. Electron. Commun. (AEÜ) 119 (2020) 153177 Contents lists available at ScienceDirect International Journal of Electronics and Communications (AEÜ) journal homepage: www.elsevier.com/locate/aeue