Meta-grounded bandpass filter with broad upper-stopband

In this paper, a novel meta-grounded planar bandpass filter is presented, facilitating much broader upper stopband. The proposed filter is comprised of a strip layer on the top, a dielectric laminate in the middle and a meta-grounding layer on the bottom. The strip on the top consists of three cross-shaped resonators in cascade. Instead of perfect conducting ground, a meta-ground, composed by a group of metallic mushroom lattices with different characteristic dimensions, is proposed for broadening the upper stopband. In order to validate the proposed concept, we design and fabricate a prototype filter with a center frequency of 11.6 GHz, which exhibits an extremely broad upper stopband from 17.6 GHz to 72.2 GHz with a rejection level greater than 20 dB.