Triple-Band Ultrathin Minkowski Fractal-Inspired Polarization-Insensitive Microwave Absorber for Stealth Application

A compact and ultrathin triple-band fractal-inspired polarization-insensitive absorber is presented. The proposed absorber’s unit cell comprises a Minkowski fractal-inspired structure. The measured absorption peaks of more than 90% have been demonstrated by the proposed absorber covering three bands, i.e., S-band (2.5 GHz), C-band (5.2 GHz), and X-band (9.8 and 11 GHz), having diverse applications in WLAN, 5G, and radar systems, respectively. Furthermore, to comprehend how the unit cell interacts with incident waves, the electromagnetic properties, such as permittivity and permeability and normalized input impedance, have been extracted. Additionally, simulated oblique incidence angle insensitivity and polarization angle stability for angles up to 60° have been demonstrated by the proposed absorber. This proposed multiband absorber has a thickness of 0.013 λ and unit cell periodicity of 0.150 λ (corresponding to the lowest resonant frequency) making it an ultrathin and compact design. A prototype of an 11 × 11 array of unit cells of the absorber has been fabricated and tested. The measured absorptivity and polarization angle insensitivity closely matches the simulation results. Thus, the proposed work will be of great use in multiuser, multiband environments with enhanced security of RF applications as well as in stealth technology.