Design of Ultra-thin Absorbers Embedded with Fractal Frequency Selective Surface in Low Frequency

Ultra-thin absorbers at low frequency bands composed of two traditional microwave absorbing material (MAM) rubber plates and fractal frequency selective surface (FSS) were designed. The absorbing properties of composite absorbers of different arrangement of MAM and FSS were investigated in detail in L and S bands. Two traditional MAM rubber plates and fractal FSS layers were fabricated for producing the multilayer microwave absorber (MMA) samples by using vulcanizing and laser etching methods, respectively. The reflectivity of MMA samples were measured by the NRL-arch testing systems. It is found that introducing FSS layers into the traditional MAM plates indeed could strengthen the absorbing properties of MMA samples at low frequencies. Moreover, after proposing double FSS layers in a proper arrangement, the MMA sample with the thickness of only 1.8 mm could obtain peak value of –9.35 dB and the reflectivity value of –3.49 dB at 1 GHz, respectively. As a result, the introduction of fractal FSS layers could provide another way to develop the absorbing properties at low frequency bands.