Design of Compact Microstrip Lowpass Filters Using a U-Shaped Defected Ground Structure and Compensated Microstrip Line

A compact microstrip lowpass filter using a U-shaped defected ground structure (DGS) with compensated microstrip is proposed in the paper. The equivalent circuit for the proposed U-shaped DGS and its corresponding L-C parameters are extracted by using its S-parameters response and a simple circuit analysis method. The lowpass filter using three cascaded U-S DGS provides a compact size, very good transition sharpness with low insertion loss in passband and wide rejection in the stopband. Measured results show good agreement with the theoretical results