Electromagnetic Bandgap Structure

Containing High-k Dielectric Ceramics

Electromagnetic bandgap structure (EBG) is an artificial dielectric composite, in which dielectric materials with high and low permittivities are periodically arranged in space. EBG can be regarded as an electromagnetic version of semiconductor. In analogous to the electronic energy bandgap structure in semiconductor (due to the periodicity of the semiconductor lattice), EBG possesses a electromagnetic wave bandgap structure. EBG provides a new way of controlling electromagnetic waves.

Three structure features determine the bandbap structure: 1, the periodicity; 2, the high and low permmitivities ratio; and 3, the volume ratio of the two materials. This project aims to introduce a microwave high permittivity (high-k) ceramic BiNbO4 doped with V2O5 (BVN) into the EBD design, with the aim to increase the permittivity ratio so that the EBG shows a wider bandbap. The project also explores the complex shape forming of the periodic ceramic structures.

Two dimensional square lattice EBG containing a series of BVN ceramic pillars surrounded by polymethyl methacrylate (PMMA) polymer was fabricated by the dice-and-fill technique.

The bandgap structure was calculated using software HFSS. By adopting a periodic boundary condition, the problem domain was reduced to a unit cell. Because of the introduced high-K dielectrics and the large contrast of dielectric permittivities (permittivity of BVN=43; permittivity of PMMA=2.5), the EBG possesses superior properties compared with previous implementations in terms of gap bandwidth and practicability. Two transverse magnetic (TM) bandgaps can be seen on the bandgap structure.

Using a transmission/reflection method, the transmission parameter of the prototype sample from 7 to 19 GHz was measured, and a gap width up to 44% has been demonstrated.

A three dimensional EBG with a diamond lattice periodicity has the advantage of generating a complete bandgap blocking electromagnetic wave propagation in any direction. A unit cell can be used to calculate the bandgap structure.

Three dimensional printing together with lost mold sintering were used to fabricate a ceramic EBG with the diamond periodicity.

The fabrication result. A gap width of 153% (gap band width/central frequency) was demonstrated.

[1] Zhiyuan Shen, Hong Wang, Jianzhang Shi, and Xi Yao, “Electromagnetic bandgap structure containing high-K dielectric ceramics”, J. Am. Ceram. Soc., 91[9], (2008), pp. 2892-2896.

[2] Zhiyuan Shen, Hong Wang, Jianzhang Shi, “Electromagnetic bandgap structure containing high-K dielectric ceramics”, Chinese Physical Society 2007 Fall Meeting, Sep, (2007), Nanjing, China. (oral presentation)

[3] Wei Dai, Hong Wang, Di Zhou, Zhiyuan Shen, Yong Li, and Dichen Li, “The ultra-wide band gap property induced by lattice period gradually changing in three-dimensional photonic crystals”, J. Am. Ceram. Soc., 93[12], (2010), pp. 3980-3982.