用磁性异向介质抑制共面天线间的表面波

从电磁波传播原理上说明可用磁性异向介质抑制舰载共面相控阵天线间的表面波,利用时域有限积分法在CST Microwave Studio中对理想导电体(Perfect Electric Conductor,PEC)平面上两个天线端口的仿真模型进行全波求解计算,结果表明:磁性异向介质不但可以在等效磁导率实部为负的频段内增大天线间的隔离度,而且在某些频率还能降低阵面天线模型的后向散射值,并分析了异向介质厚度的变化对电磁兼容性和整体隐身性的影响,异向介质厚度的选择与其电磁本构参数的确定同等重要.     

应用于THz波的非对称双开口环传输特性研究

设计并制备了一种适用于太赫兹波段的非对称双开口环结构,数值仿真和实验测量了其传输性质.结果表明,垂直极化时样品在低频的0.540 THz和0.925 THz处存在谐振点,来源于左右两开口环的LC谐振,电流和电场分布主要集中在两开口环的开口处;而在高频处(1.885THz)谐振点的表面电流具有相反的两个环流方向,电流和电场分布于整个样品表面,此处的谐振来源于两开口环耦合后的偶极子谐振.当太赫兹波平行极化该样品时,原来两个低频的LC谐振消失.实验测量结果与数值仿真具有很好的一致性.此结构超材料的传输特性研究对太赫兹波调制器、滤波器、吸收器及偏振器等器件设计和制备具有一定的指导意义.     

Appropriate truncation for photonic crystals

Effective properties of one-dimensional photonic crystals in the resonance domain are investigated. The obtained analytic expressions of effective permittivity and permeability lead to several results. Firstly, in the case of lossless materials, effective permittivity and permeability take, in general, complex values. It is shown that these values are governed by the truncation of the boundary layer. Considering the particular case of a symmetric unit cell, the effective permittivity and permeability become purely real and, by the way, coherent with physics. Finally, in this case with a symmetric unit cell, we show that effective permittivity and permeability can stay nearly constant in a wide range of wavevectors including propagating and evanescent waves.     

Effects of higher order nonlinearities on modulational instability in nonlinear oppositely directed coupler

We are motivated by recent studies in medium formed by two tunnel-coupled waveguides. One of the waveguides is manufactured from an ordinary dielectric, while the second has negative refraction. We present an investigation of the gain spectrum permitting modulation instability in the nonlinear optical coupler with a negative-index metamaterial channel whose non-linear response includes third- and fifth-order terms. The principal motivation for our analysis stems from the impact of the inevitable presence of the effective cubic–quintic nonlinearity. We emphasize the influence of higher order nonlinear terms, over the MI phenomena, and the outcome of its development achieved by using linear stability analysis. Gain spectrum investigation has been carried out for both anomalous and normal dispersion regime in the focusing and defocusing cases of nonlinearity and near-zero dispersion regime where higher order linear dispersive effects emerge. Our results show that the MI gain spectra consist of multiple spectral region which are symmetric to the zero point. Moreover, some spectra have a high cut-off frequency but a narrow spectral width, which is obviously beneficial to the generation of high-repetition-rate pulse trains.     

Square-tooth split ring resonator – a novel metamaterial for bandwidth and radiation improvement in microstrip-based radiating structure design

A square multiband truncated microstrip patch antenna was investigated using a square-tooth split ring resonator for multiband applications in both S- and C-bands. The square-tooth split ring resonator is formed from metallic inclusions in a substrate to create a metamaterial. We introduce a new square-tooth split ring resonator which increases the radiation of the antenna as well as the bandwidth. This new design creates a slow wave structure. The square-tooth addition to the split ring resonator works like a slow wave structure. The square-tooth split ring resonator design is compared with the simple split ring resonator design. The square-tooth design has four bands with center frequencies of 3.88, 4.81, 5.4, and 5.62 GHz, whereas design with the simple split ring resonator has just three bands with center frequencies of 3.88, 4.74, and 5.50 GHz. The bandwidth is increased by 20% to 30% using the square-tooth split ring resonator compared to the simple split ring resonator.     

Complementary split ring resonator metamaterial to achieve multifrequency operation in microstrip-based radiating structure design

Following recent findings on metamaterials, a miniaturized microstrip patch antenna loaded with a complementary split ring resonator (CSRR) was investigated for multiband operation. The proposed structure has a CSRR loaded in the base of the antenna to improve its performance and to make it a metamaterial. Metamaterials exhibit qualitatively new electromagnetic response functions that cannot be found in nature. The CSRR-loaded base allows simultaneous operation over several frequencies. Here, a total of seven bands were achieved by loading the patch antenna with the CSRR. The seven bands were centered around frequencies of 4.33 GHz, 5.29 GHz, 6.256 GHz, 7.066 GHz, 7.846 GHz, 8.86 GHz, and 9.75 GHz. Design results were obtained by using a high-frequency structure simulator that is used for simulating microwave passive components.     

Aligned Ag nanowires for radiation manipulation: efficient and broadband infrared polarizing beam splitter

We developed a numerical method to model and design infrared (IR) devices based on aligned metal nanowires on a flat substrate. Homogenization techniques and the transfer matrix method for birefringent-layered materials have been combined to obtain a simple but effective tool for tailoring and optimizing the optical properties of the resulting, strongly anisotropic system. As an example, we show the design of an efficient, broadband, IR polarizing beam splitter. With the emerging of new self-assembling techniques allowing orientation of metallic nanowires in uncomplicated and less-expensive ways, our results show a route to get a class of efficient, low cost and broadband IR polarizers.     

Left-handed metamaterials based on only modified circular electric resonators

Abstract

The novel design of a single-sided left-handed metamaterial (LHM) based only on modified circular electric resonators (MCERs) is presented experimentally and numerically in this letter. A capacitive gap is introduced in the middle arm of the electric resonator. Through adjusting the geometrical dimensions properly, the two frequency bands corresponding to negative permittivity and permeability overlap, which is validated by the parametric retrieval algorithm and equivalent circuit analysis. Furthermore, a dual-band LHM is achieved by combining two kinds of MCERs within the same unit cell. Compared to previous composite structures, the MCERs have the advantages of simple pattern, flexible design and fabricating three-dimensional LHMs readily.