Sharp roll‐off lowpass filter using interdigital DGS slot

Abstract

A novel lowpass filter (LPF) with a sharp roll-off and a wide stopband is presented. The proposed LPF is based on a dual-plane structure with an interdigital shape defected ground structure (DGS). The DGS exhibits a sharp roll-off and three transmission zeros. By tuning the length of the fingers, the resonant frequency can be easily changed. Based on the proposed DGS, a LPF has been designed, fabricated and measured. The transition band is from 3.11 (f c) to 3.23 GHz with −3.02 and −22.5 dB, respectively. The stopband with rejection better than 25 dB can be extended to 3.4 f c .

Ultra Sharp Transition-Band LPF with Miniaturized Size for GSM Applications

“…To develop the stop-band of the low-pass filter in [11], improved hairpin resonators were adopted; nonetheless the transition-band is slow. Multi-layer LPFs such as defected ground structure (DGS) [12][13][14][15][16][17][18][19], do not have a wide stop-band and sharp transition-band, moreover these filters suffer from complex structure.…”

Study of compact microstrip lowpass filter with improved performance using defected ground structure

“…Various shapes of DGSs viz. dumbbell‐shaped, rectangular slot and metal‐loaded slots, cross‐shaped, complementary split‐ring resonator shaped, H‐shaped, elliptic‐shaped, fork‐shaped, modified Pi‐shaped, interdigital‐shaped, U‐shaped, and V‐shaped DGSs are described in the literature which demonstrate their technical viability and applications.…”

“…Certain shapes of DGSs, such as H‐headed dumbbell‐shaped, elliptic‐shaped, and fork‐shaped have less defected ground area and provide improved performance as compared with dumbbell‐shaped. Modified Pi‐shaped DGS and interdigital‐shaped DGS provide sharper transition response with good passband performance. In Ref.…”

Miniaturized lowpass filter with wide band rejection using modified stepped-impedance hairpin resonator

“…In modern wireless communication systems, small‐sized lowpass filters (LPFs) with wide stopband rejection are in high demand for suppression of noises and spurious signals. Various methods have been researched to achieve LPF with good performance, such as cascading resonators , using semilumped component approach and employing defected ground structure (DGS) and electromagnetic band‐gap (EBG) . However, the former two would increase the circuit size, and the latter would cause circuit complexity by breaking the ground plane and potentially increasing the radiation of the filter.…”

“…In Ref. , an interdigital shaped DGS was used to achieve LPF with sharp roll off. Despite the merits mentioned above, it should be noted that no appreciable advantage in size reduction was achieved.…”