Central E shaped stub loaded stepped impedance resonator for multiband filter application

In this paper, a multiband filter using two centrally E shaped stub loaded stepped impedance resonator (SLSIR) is presented. Due to the presence of stub loading in the single mode open loop ring resonator, dual mode is achieved. The band pass responses are achieved due to the fundamental odd and fundamental even mode resonant frequency and also with first three even mode higher order resonant frequencies. The four center frequencies are located at 0.90 GHz, 2.08 GHz, 3.40 GHz and 4.60 GHz and fractional bandwidths are 16.7%. 6.96%, 5.84%, 1.79% respectively. Also return loss exceeds 15.35 dB and insertion loss is underneath 0.92 dB.