Application of a Defected Ground Structure and Alternative Transmission Line for Designing a Quasi-Elliptic Lowpass Filter and Reduction of Insertion Loss
A new defected ground structure (DGS) consisting of two square ring slots connects with a rectangular ring slot by two thin transverse slots under a microstrip line is proposed. In the frequency characteristics of proposed unit pattern, an attenuation zero is observed close to the attenuation pole. As a result, better transition sharpness, lower passband insertion loss and broader stopband are observed compares to dumbbell DGS. An equivalent lumped L-C network is proposed to model the introduced DGS unit and corresponding parameters are extracted. Insertion loss is reduced by alternative transmission line on the top plane of the DGS unit. (C) 2010 Wiley Periodicals, Inc Int J RF and Microwave CAE 20 682-688, 2010
lowpass filter microstrip, defected ground structure, elliptical