基于超材料结构实现5.8GHz RFID天线小型化设计

设计出一款可应用于RFID（Radio Frequency Identification）系统的5.8GHz传统矩形微带天线,天线辐射贴片尺寸为15.74mm×11.12mm,天线的回波损耗（S11）的实测结果为-23.276dB。此后,在矩形微带天线基础上进行设计改进,通过分别蚀刻15个超材料结构I型谐振环和6个超材料结构开口谐振环(Split Resonant Ring, SRR),构造出两款新型小型化天线。与传统矩形天线相比,在保持方向性、最大增益等参数性能基本不变的条件下,基于超材料结构的天线辐射贴片尺寸分别为12.44mm×9.12mm 和11.74mm×9.1mm,相比传统矩形天线分别缩小了35.2%和41.82%,辐射贴片小型化效果明显,其回波损耗实测结果分别为-21.83dB 和-15.40dB。     

Universal theorems for total energy of the dynamics of linearly elastic heterogeneous solids

In this paper we consider a sample of a linearly elastic heterogeneous composite in elastodynamic equilibrium and present universal theorems which provide lower bounds for the total elastic strain energy plus the kinetic energy, and the total complementary elastic energy plus the kinetic energy. For a general heterogeneous sample which undergoes harmonic motion at a single frequency, we show that, among all consistent boundary data which produce the same average strain, the uniform-stress boundary data render the total elastic strain energy plus the kinetic energy an absolute minimum. We also show that, among all consistent boundary data which produce the same average momentum in the sample, the uniform velocity boundary data render the total complementary elastic energy plus the kinetic energy an absolute minimum. We do not assume statistical homogeneity or material isotropy in our treatment, although they are not excluded. These universal theorems are the dynamic equivalent of the universal theorems already known for the static case [Nemat-Nasser and Hori, 1993] and [Nemat-Nasser and Hori, 1995]. It is envisaged that the bounds on the total energy presented in this paper will be used to formulate computable bounds on the overall dynamic properties of linearly elastic heterogeneous composites with arbitrary microstructures.     

Tuning the optical properties of metamaterials based on gold nanowire arrays embedded in alumina

We fabricated a series of gold nanowires/alumina composite films with different wire lengths. Optical transmission measurements confirmed that the composite films exhibit transverse and longitudinal surface plasmon resonances. We show that the wavelength of the longitudinal resonance is sensitive to nanowire length, while that of the transverse resonance is not. The experimental results are in agreement with the modeled results based on the Maxwell Garnett effective medium theory. Moreover, the window for negative refraction of the samples can be tuned in synchronism with the longitudinal resonance by the nanowire length.     

Metamirror channel structures: Optical properties

A new kind of metamaterial based on hierarchically organized mirror channels with partially reflecting walls, metamirror structures (MMS), is proposed. Properties of MMS are close to those exhibited by left-handed materials, despite the difference in underlying physical mechanisms. Transmission and reflection of rays are considered for different MMS geometries and types. It is shown that a one-step reflective 2D MMS based on rectangular elementary unit cells, being properly curved, possess the properties of a lens, and a generalized law describing MMS-based lenses is presented. If the MMS have relatively small sizes of unit cells (from one to tens of micrometers), then they may be treated as solid materials with anomalous optical properties in a wide range from visible and near-infrared up to UV wavelengths. It is concluded that MMS features may be observed in metamaterials of other kinds.     

Gain control and diffraction-managed solitons in metamaterials

The question of whether stable, active metamaterials can be created is addressed, both through a discussion of absolute instability and an analysis of a transmission line that produces dispersion analogous to that of the familiar split-ring resonator/wire-based metamaterial. The gain is introduced using negative conductance diodes and it is shown that the frequency bandwidth controls the stability window. The diodes are located as lumped elements in the unit cell. It is demonstrated that the production of an, active, negative phase (left-handed) frequency window, with spatial amplification is possible. The paper then goes on to assume that since loss can be controlled in this way special types of solitons can be created from phase and loss compensation and they could be the basis of future computational devices. The candidates selected are diffraction-managed spatial solitons and their basic properties are displayed numerically.     

Ka波段平面Goubau线与超材料相结合的宽带滤波器

平面Goubau线(PGL)可作为单导体波导进行Ka波段表面电磁波传输。通过与超材料共面集成,可抑制PGL特定频点的表面波。在此基础上将超材料组成阵列形式,实现了宽带滤波特性。采用CST对所设计模型进行仿真,通过设置场监视器,重点研究了PGL与超材料的场分布特征与互作用结果。通过不断优化设计,最终获得了20%相对带宽的宽带滤波器。Ka波段平面器件的研究有助于微波毫米波器件小型化、平面化、集成化方向的发展。     

Design and analysis of a super compact wide-band bandpass filter based on metamaterial resonators

In this paper, a novel compact wide-band bandpass filter (BPF) with a wide frequency range is presented. This filter consisting of a multi-mode resonator (MMR) and four metamaterial unit-cells benefits from a very compact size. Unit-cells based on a complementary spiral resonator (CSR) including a metallic via, improve both upper and lower stopband rejection and compensate the insertion loss (I.L) within the passband altogether. This wide-band filter presents a 3-dB bandwidth of 7.7 GHz, ranging from 3 GHz to 10.7 GHz and the Insertion loss is less than 0.7 dB over the passband. The measured results are in good agreement with both the full-wave electromagnetic simulation and the proposed circuit model results. The dimension of the fabricated filter is 0.128 λ × 0.1 λ (i.e., 5.6 × 4.4 mm²). This filter is considerably compact compared to the other wide-band bandpass filters with the same substrate.     

Infrared resonances of local fields and ellipsometric spectra of negative-refraction metamaterials

Suitable combinations of the optical response and geometrical form of flat or curved interfaces of the constituents in nanometer-sized metamaterials can lead to a strong enhancement of local fields, seen typically as sharp spectral resonances in optical spectra. We propose a classification of the resonant phenomena in inhomogeneous systems within the effective-medium approximation, and examine their manifestation in infrared ellipsometry. We report mid-infrared ellipsometric spectra of a doped semiconductor metamaterial, exhibiting negative refraction. We provide a simple explanation for the difference in the directions of the phase- and energy propagation. The resonance responsible for a strong anisotropy and the interesting behavior of refracted light is found to lead to characteristic features in the ellipsometric spectra.