Aperture-backed microstrip stepped impedance resonator with ultra-broad rejection bandwidth

An improved microstrip stepped impedance resonator (SIR) with backed aperture is developed for the purpose of effective suppression of multiple spurious resonances. By backing the aperture at the centre and widening the strip widths at two sides, this novel SIR with miniaturised size achieves the ultra-broad rejection bandwidth of 4.0 to 17.6 GHz, as exhibited in the simulated and measured results.