Design of low-pass filters using some defected ground structures

We present characteristics of seven types of simple and complex defected ground structures (DGS) slot to realize the quasi-lumped inductance. A simple DGS follows the Butterworth type response; whereas a complex DGS has quasi-elliptic response. The response of DGS has strong influence on the performance of a 5-pole Chebyshev type low-pass filter (LPF). We present a systematic design process to realize the LPF using these DGS slots. The 5-pole open square (OS) DGS based LPF of cut-off frequency 2.5 GHz provides best measured performances-transition region bandwidth 0.53 GHz, 20 dB rejection band-width 14.7 GHz, insertion loss 1.29 dB. Theses performances are better than the reported results of the 5-pole DGS based LPF in literature.