A compact highly-selective filter inspired by Negative-Refractive-Index Transmission Lines

A Negative-Refractive-Index Transmission-Line (NRI-TL) inspired filter is realized by replacing the traditional shunt inductive loading with a series LC resonator to ground. Design equations for the filter are compared with full-wave simulations and experimental results are presented for a highly-selective folded implementation exhibiting 5% bandwidth at 2.03 GHz , 1 dB insertion-loss and a maximum band-edge slope of 2.15 dB/MHz.