Investigations on fractal square loop FSS at oblique incidence for GSM applications

This paper proposes a fractal square loop frequency selective surface (FSS) with dual-band stop behavior. The FSS elements are etched on FR-4 substrate to attenuate signals at GSM900, GSM1800 and IMT2000 frequency bands while transmitting other microwave signals. The unit cell geometry is a modification of the conventional square loop which shows an improvement in stability for oblique incidence up to 45° for both TE and TM polarizations. The proposed FSS shifts the onset of a grating lobe to the outside of the frequency of interest without compromising the target resonant frequencies. The measured results are shown to be in a very good agreement with the simulated results.