A COMPACT LOW-PASS FILTER WITH SHARP CUTOFF AND LOW INSERTION LOSS CHARACTERISTIC USING NOVEL DEFECTED GROUND STRUCTURE

Abstract

In this paper, a compact stepped-impedance hairpin resonator (SIHR) low-pass fllter (LPF) with an improved split-ring resonator defected ground structure (ISRR DGS) and two elliptical DGSs is presented. The proposed LPF exhibits the advantages of low insertion loss, sharp cutofi characteristic, wide stopband over the ordinary LPFs. The introduced DGSs are presented to improve the in- band and out-band characteristic. An equivalent RLC circuit model of the two kinds of DGSs is presented and analyzed. Combining with these two structures, a new SIHR LPF having 3dB cutofi frequency of 2.5GHz is fabricated and measured. Measured results show that the selectivity of the proposed LPF is more than 100dB/GHz and the insertion loss is less than 0.5dB in the passband. A wide stop-band bandwidth with 20dB attenuation from 2.58 up to 7.5GHz is achieved. Moreover, the occupied area is only 20 £ 25mm 2 .