A design of microstrip bandpass filter with narrow bandwidth using DGS/DMS for WLAN

Abstract

In this paper, a compact microstrip bandpass filter is designed using defected ground structure (DGS) with narrow bandwidth. Here a 50Ω quarter wave microstrip line is used for designing the bandpass filter. A circular head dumbbell shaped DGS in the ground plane of a microstrip line is used which provides the bandstop characteristics. Two series gap slot is introduced for achieving the bandpass characteristics in the conducting strip. These slots in conducting strip are also called defected microstrip structure (DMS). This arrangement provides better coupling in the pass band. In this paper no stubs and via are used. The bandwidth of the filter is 500 MHz and insertion loss less than 0.5 dB in passband at 5.4 GHz. The measured insertion loss (S21) is 0.6 dB at the center frequency 5.4 GHz with a bandwidth of 500 MHz which is good in agreement with measured results after the fabrications)