Miniaturized bandpass filter based on metamaterial resonators: a conceptual study

In this paper, a left-handed metamaterial coplanar-waveguide bandpass filter with a compact electrical size is proposed. The filter features a strongly improved out-of-band rejection ratio compared with conventional cascaded split ring resonator (SRR) structures while all dimensions remain well below a third of the guided design wavelength. Especially, the problem of low upper stopband attenuation is overcome. This is achieved by combining an SRR with a complementary SRR cell. We also demonstrate that this approach enables flexible filter designs for a broad range of bandwidth ratios with small insertion losses at the centre frequency of the device.