Novel Ultra Wide Band Polarisation Independent Capacitive Jaumann Radar Absorber

Abstract

An ultra wide band (UWB), reduced thickness four layers capacitive jaumann absorber (CJA) with measured reflectivity of -15 dB (minimum) from 2 GHz to 19 GHz is presented in this paper. The novel CJA is designed and implemented by modifying the jaumann absorber (JA) design. The crucial impedance matching layers of CJA are designed by conceptualizing hexagonal resistive grid on dielectric substrates. Reduced thickness of 24.8 mm is realised by capacitive loading of hexagonal resistive grids with hexagonal resistive patches. Absorption performance of CJA is verified by full wave analysis using high frequency structural simulator software. Polarisation independent absorption performance is realised. Absorption of 96.5 per cent (minimum) is achieved with variation in angles of incidence from 0° to 30°. Resistive capacitive layers of CJA are developed as electrically thin printed circuit boards and integrated with alternating low loss, low density foam dielectric spacers backed by metallic conducting plane. Size of panel CJA is 280 mm × 280 mm. Fabricated panel CJA is evaluated for radar cross section (RCS) performance in microwave anechoic chamber. Matching results are obtained in simulation and measurements. The reduced thickness, low weight, UWB CJA finds application in RCS reduction of air vehicles/unmanned air vehicle.