Improvement in Cutoff Frequency of Microstrip Butterworth Low Pass Filter using DGS Technique

Abstract

This paper presents the design, analysis and fabrication of Butterworth Low pass filter with sharp rejection response using defected ground surface technique. The work is carried out to design a low pass filter with cut-off frequency 2.5 GHz to achieved the broad frequency response; the first step is to make a rectangle of 10x10mm at ground surface and the equivalent circuit for the DGS, subsequently followed to consequent L-C parameters extraction using analysis of S parameters response (EM simulation). The designed Butterworth low pass filter is realized and optimized using DGS (Defected Ground Structure) to attain a compact size, satisfactory transition sharpness along with low insertion loss in pass band and wide rejection in the stop band. The fabricated device showed the good conformity with theoretical and VNA measured result.