Research of defected ground structure microstrip low-pass filter using stepped impedance shunt stubs structure

Defected ground structure (DGS) can change the effective permittivity of substrate materials and the equivalent circuit of the microstrip transmission line by etching the periodic or nonperiodic defected pattern on the ground plane of the microwave circuit. The traditional DGS microstrip low-pass filter has a narrow stopband, and the stopband rejection is poor. to solve this problem, the circuit structure of DGS is studied deeply . Two DGS microstrip low-pass filter circuits based on SISS structure were designed, by the adoption of rectangular defected ground structure (R-DGS), and the introduction of the rectangular stepped impedance shunt stubs (R-SISS) and semicircle stepped impedance shunt stub(S-SISS). The simulation results show that the novel DGS circuit techniques can effectively improve the RF transmission character in passband, broaden stopband bandwidth, increase stopband rejection, which are satisfactory.