Ultra-wide stopband in a compact low pass filter using stepped impedance resonators and novel techniques

The design procedure of a compact ultra-wideband (UWB) stepped impedance resonator (SIR) low pass filter, is presented in this paper. A SIR LPF with 7 GHz cutoff frequency miniaturized by meander line technique is designed and it is shown that offsetting the stepped impedance resonators, as well as indenting the tap location greatly improve rejection bandwidth. Offsetting input lines further maximizes rejection bandwidth. The proposed filter is simulated in Sonnet EM software, fabricated, and tested on a high dielectric ceramic. The results show an improved stopband performance compared with similar topologies with a drastic size reduction in the filter.