Microstrip low-pass filter with wide stopband using coupled-line hairpin unit

A novel low-pass filter (LPF) with sharp cutoff frequency response and wide rejection bandwidth is proposed in this paper. The proposed LPF is composed of microstrip coupled-line hairpin unit, semicircle defected ground structures (S-DGS) and semicircle stepped-impedance shunt stubs (S-SISS). Sharp roll-off skirt and good out-of-band rejections are achieved as demonstrated in both simulation and experiment.