Current Applied Materials 2666-7339/22 $65.00+.00 © 2022 Bentham Science Publishers 1 Navdeep Singh 1 and Gagan Deep Aul 1,* 1 Department of Electronics and Communication Engineering, DAV University, Jalandhar-144012, Punjab, India Abstract: Radar is a delicate detection device and since its evolution different techniques for reducing electromagnetic reflections have been discovered. This paper provides a concise review on fundamen- tals of absorption which reduce radar cross section from stealth target with which radar cross section affects the survivability and mission capability. The reduction of radar cross section depends on dielec- tric and magnetic properties of the material. The first section reviews the Radar Absorbing Material (RAM) in order to provide a background on fundamentals, various stealth techniques for absorption and its properties at microwave frequencies. The second section reviews the Multi-Walled Carbon Nanotubes and their different composites by encapsulation of other metals, polymers or epoxies into it and its microwave absorption properties were studies at microwave frequencies. Multi-Walled Carbon Nanotubes based composites for microwave absorption are reviewed on the basis of various factors; material composition, reflection loss performance, thickness, complex permittivity, complex permea- bility, dielectric tangent loss, magnetic tangent loss, bandwidth, and frequency band. A R T I C L E H I S T O R Y Received: November 03, 2020 Revised: April 21, 2021 Accepted: May 02, 2021 DOI: 10.2174/2666731201666210803110914 Keywords: Radar Absorbing Material (RAM), carbon nanotubes (CNTs), microwave absorption, reflection loss, thickness, bandwidth. 1. INTRODUCTION Radar waves are electromagnetic waves with wave- lengths ranging from one to one meter or equal to the fre- quency of 300MHz-300GHz. The elementary nature of mi- crowave is usually introduced by its three fundamental properties penetration, absorption and reflection. Microwave absorbing materials have been fascinating greater attention due to the increasing usage of electromagnetic waves, which further increases electromagnetic interferences problems and because they are vital parts of the stealth technology in all military and defense platforms. So, it is possible to min- imize the reflectivity of Microwave Absorbing Materials (MAM) by using various applications like radar cross sec- tion reduction, safe microwave ovens, designing microwave circuits, antenna pattern shaping, anechoic chambers and EMI reduction. Evolution of radar absorbing materials began in the 1930's after the rise of radar. Absorber architecture com- bined material with different loss methods and used physical magnification to maximize reflection loss over large band- widths. Therefore, absorbers come with various patterns and designs to reduce the coefficient of reflection and give max- imum absorption in accordance with the necessary condi- tions. Standard commercial technology at microwave frequencies drives the creation of an absorber with frequency selective *Address correspondence to this author at the Department of Electronics and Communication Engineering, DAV University, Jalandhar-144012, Punjab, India; Tel: +91-98880-52750; E-mail : gaganaul79@gmail.com surface. Microwave absorbers are materials which diminish the radio waves. Absorbers are used in a wide variety of purposes to minimize or remove unnecessary radio waves which may interfere with the operation of a device [1]. The fundamental principle of absorption in case of radar is to reduce Radar Cross Section (RCS) and Reflectivity. RCS is reduced by different methods under different conditions and requirements. The first method that evolved for RCS reduc- tion was shaping. The aim of shaping is to choose an ob- ject's external description to redirect reflected radar waves back in other directions, except back to the radar. But shap- ing has some limitations from the view of manufacturing industry because they cannot compromise with system de- signs just for the sake of RCS reduction. Despite this, the developers can use Radar Absorbing Material to coat deli- cate sections of the target. This is the most widely used method for RCS reduction by the absorption of electromag- netic waves by the material itself. Certain solutions to pre- vent target identification and electronic countermeasures include passive and active cancelation approaches, in addi- tion to forming and radar absorbers. Effective cancelation is better suited for lower frequency radar cross section reduc- tion, where absorber usage and shaping become challenging [2].The Radar Absorbing Material (RAM) is designed to remove incident energy and thus decrease the energy trans- mitted or reflected back to the radar. There are two tech- niques available at radar frequencies for reducing reflections from a target surface, i.e. absorption and cancelation. Ab- sorption is the transmission in space of electromagnetic wave to the absorber as it passes through. Electromagnetic energy is consumed by different processes of loss, which Send Orders for Reprints to reprints@benthamscience.net Current Applied Materials, 2022, e050821195213 MINI-REVIEW ARTICLE Carbon Nanotubes based Composites for Electromagnetic Absorption - A Review