A Novel Triple-Mode Bandpass Filter Based on a Dual-Mode Defected Ground Structure Resonator and a Microstrip Resonator

Abstract

A novel triple-mode bandpass filter (BPF) using a dual-mode defected ground structure (DGS) resonator and a microstrip resonator is proposed in this paper. The dual-mode characteristic is achieved by loading a defected T-shaped stub to a uniform impedance DGS resonator. A uniform impedance microstrip resonator is designed on the top layer of the DGS resonator and a compact bandpass filter with three resonant modes in the passband can be achieved. A coupling scheme for the structure is given and the coupling matrix is synthesized. Based on the structure, a triple-mode BPF with central frequency of 2.57 GHz and equal ripple bandwidth of 15% is designed for the Wireless Local Area Network. Three transmission zeros are achieved at 1.48 GHz, 2.17 GHz, and 4.18 GHz, respectively, which improve the stopband characteristics of the filter. The proposed filter is fabricated and measured. Good agreements between measured results and simulated results verify the proposed structure well.

Multitransmission Zero Dual-Band Bandpass Filter Using Nonresonating Node for 5G Millimetre-Wave Application

“…Dual-mode open-loop resonators are well known for their compact size, which is much smaller than the conventional dual-mode loop resonator [15][16][17]. Dual-mode openloop filters can excite two nondegenerate modes as well as two controllable finite-frequency transmission zeros, which can be controlled simply by varying the size of perturbation.…”

“…By directly comparing (11) and (13), we get the elements of the coupling matrix of the cascaded cell in Figure 4(a) in terms of the elements of the cell with an internal nonresonating node in Figure 4(b), described by (14)- (16).…”

“…Additionally, two dual-mode open-loop resonators are employed in this filter. Dual-mode openloop resonators are well known for their compact size and have been used for bandpass filter design in [15][16][17], which only use a single type of resonator and show good performance. Hence, the dual-mode open-loop bandpass filters in millimetre-wave applications are worthy of study.…”