This paper focuses on a tutorial overview of defected ground structure (DGS). The basic conceptions and transmission characteristics of DGS are introduced and the equivalent circuit models of varieties of DGS units are also presented. Finally, the main applications of DGS in microwave technology field are summarized and the evolution trend of DGS is given.

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An Overview on Defected Ground Structure

Slots or defects integrated on the ground plane of microwave planar circuits are referred to as Defected Ground Structure. DGS is adopted as an emerging technique for improving the various parameters of microwave circuits, that is, narrow bandwidth, cross-polarization, low gain, and so forth. This paper presents an introduction and evolution of DGS and how DGS is different from former technologies: PBG and EBG. A basic concept behind the DGS technology and several theoretical techniques for analysing the Defected Ground Structure are discussed. Several applications of DGS in the field of filters, planar waveguides, amplifiers, and antennas are presented.

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Defected Ground Structure: Fundamentals, Analysis, and Applications in Modern Wireless Trends

A compact double equilateral U-shaped defected ground structure (DGS) unit is proposed. In contrast to a single finite attenuation pole characteristic offered by the conventional dumbbell DGS, the proposed DGS unit provides dual finite attenuation poles that can be independently controlled by the DGS lengths. A 2.4-GHz microstrip lowpass filter using five cascaded double U-shaped DGS units is designed and compared with conventional DGS lowpass filters. This low pass filter achieves a wide stopband with overall 30-dB attenuation up-to10 GHz and more than 42% size diminution.

Miniaturized microstrip lowpass filter with wide stopband using double equilateral U-shaped defected ground structure

An open-structure eigenvalue problem of substrate integrated waveguide (SIW) cavity structures is investigated in detail by using a finite-difference frequency-domain method, and the quality (Q) factor of such SIW cavities is given. Based on the concept of a defected ground structure, a new class of SIW cavity bandpass filters are designed, fabricated, and measured around 5.8 GHz. With their fabrication on standard printed circuit boards, such filters present the advantages of high-Q factor, high power capacity, and small size. Simulated and measured results are presented and discussed to show promising performances of the proposed filters.

Novel substrate integrated waveguide cavity filter with defected ground structure

Three-dimensional structures in a multi-layer ceramic substrate are important in realizing ceramic-based meso- and micro-systems. During lamination and/or co-firing, three-dimensional structures, especially those with suspended structures, tend to deform and sag due to the intrinsic nature of the green (un-fired) ceramic material. Fabrication of three-dimensional structures with well-controlled dimensional stability and mechanical integrity remains a challenge. This paper discusses the challenges in fabricating structures in a multi-layer ceramic substrate. An overview is provided of the current state of the art in patterning and lamination techniques for the fabrication of these three-dimensional structures.

Overview on fabrication of three-dimensional structures in multi-layer ceramic substrate

In this paper, a novel equivalent circuit and modeling method for a defected ground structure is proposed to design an optimized DGS lowpass filter circuit The equivalent circuit presented in this paper has parallel capacitance to explain the fringing fields due to the defects on the metallic ground plane Several comparisons between the EM-simulations on the DGS circuits and circuit simulations on its equivalent circuits are demonstrated to show the validity of the proposed model Optimization for the DGS circuit is carried out by using the proposed equivalent circuit Simulation and measurements on the fabricated DGS lowpass filter show optimized passband and stopband performance

A novel equivalent circuit and modeling method for defected ground structure and its application to optimization of a DGS lowpass filter

Since the manufacturing process does not allow solid ground planes between ceramic layers to isolate the signal lines, the buried ground should be realized as a meshed ground plane. Both characteristic impedances of the signal lines and couplings between different signal layers are influenced by the properties of these meshed planes. In this paper, we propose a new analysis method for coupling behavior between internal transmission lines, which are isolated by the buried meshed-ground planes. The coupling behavior between layers isolated by meshed-ground plane is investigated by the coupled-transmission lines model for the isolated layers. The coupling factors between isolated lines with the meshed-ground are extracted by 2-D FEM calculations.

Jong-Hun Lee

Papers

A novel equivalent circuit and modeling method for defected ground structure and its application to optimization of a DGS lowpass filter

Analysis of coupling characteristics between transmission lines with a buried meshed-ground in LTCC-MCMs