High selectivity lowpass filter using negative-ε metamaterial resonators

A binomial lowpass filter provides the flattest passband response but slow attenuation transition. Presented is a design for improving roll-off performance based on the negative-ɛ property of complementary split ring resonators, while maintaining filter passband performance with smaller size. Measured results indicate that the proposed structure achieves a flat passband with no ripples as well as having a selectivity of 32 dB/GHz. This significantly exceeds the 17 dB/GHz selectivity of the conventional design. Furthermore, the proposed filter has a smaller size by 16%.