A compact microstrip lowpass filter using a U-SGS, which has the same meaning as U-Defected Ground Structure (U-DGS), with compensated microstrip is proposed in the paper. The equivalent circuit for the proposed Ushaped DGS and its corresponding L-C parameters are extracted by using its Sparameters response and a simple circuit analysis method. The lowpass filter using three cascaded U-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. New ideas in order to improve the compactness and the losses of the filter have been proposed. The article presents some promising patents on design of compact ultra-wide stopband lowpass filter using a U-slotted ground structure (SGS) and multilayer-technique.
Keywords: Defected ground structure, lowpass filter, multiplayer-technique, reject band, sharp transition, U- resonator, U - Slotted Ground Structure, Ultra-Wide Stopband Lowpass Filter, U-DGS SLOT STRUCTURE, U-DGS SLOT, DESIGN AND FABRICATION