Miniaturized low-pass filter based on defected ground structure and compensated microstrip line

This article presents a low-pass filter combining asymmetric pi-type defect structure and microstrip line filter. Traditional single-form defected ground structure filters often require cascading to have good suppression, which can result in increasing board size and cost. The top layer of the proposed filter is in the form of a stepped impedance microstrip line, and the bottom layer uses a defective structure. Simulation and experimental results show that the filter combining the new defect structure and the microstrip line has a very sharp transition zone and deeper suppression depth than the existing symmetrical or asymmetric defect structure. The proposed structure has an ultracompact size of 356 mm(2), and the results show an insertion loss from 0 to 2.2 GHz as low as 0.8 dB and a wide stop band of more than 30 dB from 3.3 to 9.8 GHz.