Improvement in Roll off Factor of Low Pass Filter Placed on an EBG Substrate

Abstract

Filters have always remained a field of immense interest in the high frequency domain. Emerging applications such as wireless communications continue to challenge RF/microwave filters with ever more stringent requirements – high performance, smaller size, lightweight, and lower cost. In this paper we propose and investigate the application of electromagnetic bandgap (EBG) structures for improving the performance of a defected ground state (DGS) based low pass filter (LPF) with T-slot on the microstrip line. Whereas the T-slot and DGS are known to improve the roll off factor, EBG substrate further enhances this factor significantly. In our case the LPF with T-slot and square dumbles on DGS give a roll off of −29.3823 dB/GHz, on application of the EBG it improves to −31.7919 dB/GHz. Also, on applying the TE mode boundary condition along the vertical axis, we observe that the maximum attenuation is improved significantly from −60.65321 dB to −69.64911 dB.