Polarization Insensitive Dual Frequency Microwave Absorber for X and Ku Band Applications

Abstract

A planar microwave absorber with dual-band characteristics in X and Ku bands is presented in this paper. The proposed design operates at 8.2 GHz and 17.5 GHz with absorptivities of 99.11% and 99.39% respectively. The unit cell is designed using FR-4 substrate (εr = 4.4) with thickness 0.02λ0 and has dimensions of 0.27λ0 x 0.27λ0, where λ0 is the free-space wavelength at lowest operating frequency. The structure consists of one larger square ring corresponding to an absorption peak at X band. Further, four right angled bends are etched on the four corners of the square unit cell so as to form a another square ring of smaller dimension that corresponds to another absorption peak at Ku band. The larger square and the right angle bends are interconnected with a narrow conducting strip to improve the absorptivity in both the bands. The unit cell is examined under various polarization angles and it is polarization insensitive up to 60° and exhibits good angular stability. The fractional bandwidth of the proposed absorber is 2.4% centered at 8.2 GHz and 1.14% centered at 17.5 GHz. The high absorptivity makes it a useful candidate to absorb the undesired radiations of various electronic circuits in satellite and radar applications that degrade the performance of entire system. thereby enhancing the performance and reliability the communication systems that emit spurious radiations.