# A Metamaterial Inspired AMC Backed Dual Band Antenna for ISM and RFID Applications
## 1 Introduction  
Modern technology advancements have increased the technical requirements for RFID and ISM band systems in several sectors. The RFID technologies have proven quite popular in many industries, including manufacturing, retail, supply chain, and transportation, whereas ISM band technology is the principal band used by residential users and commercial businesses for WiFi, Bluetooth, cordless phone, printer, keyboard, mouse, and game controller applications. The ultra-high frequency (UHF) RFID tag operates in the 869 MHz-928 MHz frequency range. The Federal Communications Commission (FCC) assigns different frequencies for various purposes. The FCC reserves the 2400 and 5000 MHz frequency bands in the United States for unlicensed Industrial, Scientific and Medical (ISM) applications. The use of ISM equipment causes electromagnetic interference, which disrupts radio communications on the same frequency. As a result, this technology was limited to specified frequency ranges. Metamaterials are artificial materials with a more compact size than conventional material structures and have some infrequent properties, like a negative refractive index, negative permeability, double negative characteristic, etc., which do not exist in naturalmaterials [1]. The basic unit elements of metamaterials for improving antenna performance are the Split Ring Resonator (SRR), Complementary Split Ring Resonator (CSRR), and Electric inductive Capacitive (ELC). The SRR and CSRR structures inspired by metamaterials have been used as radiating elements to improve antenna radiation characteristics. Metamaterials are in high demand for the purpose of providing good gain and radiation efficiency due to properties, such as negative permittivity, negative permeability, and negative refractive index of the material. In recent years, some standard electromagnetic simulation techniques have been proposed for antenna engineering enhancements, such as highly reflective index, metal-dielectric metal (MDM), surface plasmon resonance absorber, double plasmon induced transparencies in aperture-coupled metal-dielectric-metal (MDM), and highly sensitive refractive index based on metamaterial [2]. Many researchers have focused on split-ring structures to improve bandwidth. Antennae using metamaterial with miniaturization techniques having a square split ring resonator (SRR) and wire strip have been proposed that operate between 1 GHz and 4 GHz frequency for Wi-max and mobile communication applications [3]. A simple structure with a metamaterial-inspired antenna covering the dual band at 2.5 GHz and 3.5 GHz can be used for wireless applications [4]. The concept of Complementary Split Ring Resonator (CSRR) was explored to get a dual band ranging with first band (1.61-1.84 GHz) resonating at 1.72 GHz and second (2.08-2.5 GHz) at 2.17 GHz with substrate dimensions of 50 \(\times\) 50 \(\times\) 1.6 mm\({}^{3}\) for mobile applications and wireless standards for input reflection coefficient and bandwidth improvement due to the presence of partial ground plane [5]. The C-shaped patch loaded with a dipole antenna was proposed, which provided dual band characteristics at UHF band (850 MHz-930 MHz) and ISM band (2.41 GHz-2.54 GHz) for RFID applications [6]. The Stealth capability of the dual band antenna was improved by loading a metamaterial absorber in the antenna by reducing the Radar Cross Section (RCS) [7]. A CPW-fed line with trapeziform ground plane and tapered impedance transformer line was employed with compactness 31.7 \(\times\) 27 \(\times\) 1.6 mm\({}^{3}\) covering between (2.595-2.654 GHz) and (3.185-4.245 GHz) to improve the antenna's impedance matching, that can be applicable for wireless communication systems [8]. A dual band AMC-back miniaturized antenna was designed for ISM frequency bands with dimensions 28.81 \(\times\) 19.22 \(\times\) 1.58 mm\({}^{3}\) at 2.45 and 5.8 GHz [9].