Paper Title
Imperatives and Desirables in Metamaterial Design for Stealth and Emi Shielding Applications

Abstract
The theory and application of metamaterials in absorption of electromagnetic waves is well established now [1]. Accordingly, its obvious application in providing stealth capability against Radars and for EMI shielding is being widely researched and employed in various ways in military as well as non-military domains [2]. While designing Metamaterial Microwave Absorber (MMA) for providing stealth capability, there are certain imperative and desirable characteristics which have to be kept in mind. These can be classified under operational, functional, material and design needs of the MMA. For obvious reasons, the MMA which needs to be deployed on the aircraft surface, has to be light, flexible and sturdy. It should have very high absorption over a fairly wide frequency band of interest. Further, the absorption characteristics should remain reasonably high under varying polarisation of the incident waves.An obliquely incident wave bounces off from the aircraft surface in direction other than the co-located receiver and hence returns fairly weak signal to the radar receiver, and not a serious concern. In view of these, certain reasonable design goals are to be decided based on the difficulties identified or encountered in the process of design, simulation, fabrication and validation. The design goals can be tweaked as per requirement and experience, without compromising on the imperatives and playing a bit with the desirables. The present investigation is aimed at reduction of effective detection range of radar by use of periodic MMAs in X-Band (8 GHz to 12 GHz). Simulations for different MMAs have been done using Microwave Studio (MWS) software provided by Computer Simulation Technology (CST). A design which takes care of the abovementioned requirements of an MMA suitable for stealth capability applications in narrow band of frequencies has been discussed. Here, absorption of the order of 60 dB and beyond for orthogonally incident waves have been achieved in narrow band [3]. Need for larger Bandwidth (more than at least 100 MHz) while maintaining high absorption (at least greater than 40 dB) has been brought out and possible methodologies for the same and their attendant difficulties have also been discussed. Increasing the operating bandwidth is the most challenging requirement. A compromise giving a reasonable solution to this challenge has been indicated. A design methodology has been proposed for evolving a suitable design of MMA for achieving such stealth capability with desired features. 1. C. Caloz and T. Itoh. “Electromagnetic Metamaterial: Transmission Line Theory and MicrowaveApplications,” John Wiley & Sons, Inc. 2006 2. S. Shang, S. Yang, L. Tao, L. Yang, and H. Cao, “Ultrathin triple-band polarization-insensitive wideanglecompact metamaterial absorber” AIP Advances, 6, 2016, 075203. 3. R. K. Mishra, R. D. Gupta, S. Datar, “Metamaterial Microwave Absorber (MMA) for Electromagnetic Interference (EMI) Shielding in X-Band”, Plasmonics, Springer US, 1-11, 2021