A deep attenuation level and wide stopband bandwidth, sharp roll-off and low insertion loss in the passband using H-shaped defected microstrip structure (DMS) at open circuit stub resonator (OCSR) of the stepped-impedance low pass filter (SILPF) is presented in this paper. The proposed filter consists of H-shaped that is etching at the microstrip line of OCSR. The OCSR is embedded in the middle of high impedance line of the SILPF. The effect of the applying H-shaped DMS is investigated through parametric studies by comparing H-shaped with Y-shaped and U-shaped. It is observed that the comparison with conventional SILPF shows that the proposed modification filter exhibit a deep and large rejected band of 27 dB attenuation level from 8.21 GHz to 23.16 GHz up to 3 fc. The proposed filter also offers sharp roll-off at 7.31 GHz cut-off frequency and maximum ripple value in the range of DC to 6 GHz is less than 0.35 dB.
