Microstrip Array with PBG Substrate

The phased array formed by microstrip antennas is analyzed using the full wave Transverse Transmission Line (TTL) method. For the microstrip patch resonator a set of equations that represents the electromagnetic fields in the x and z directions as function of the fields in the y direction are obtained applying the TTL method. The structure PBG (Photonic Band Gap) is analyzed using the homogenization theory, the objective is obtain the equivalent permittivity of structure. Numerical results of the radiation pattern for some phase excitation in a phased array are shown.     

Photoluminescence of PMMA doped with fluorescein and carbosilane dendrimer and lasing in PBG resonance cavity

Carbosilane dendrimers with terminal allyl groups were synthesized and used to encapsulate the allyl derivative of fluorescein (allyl-FL) doped in PMMA. The optical property of this system was investigated and the results showed that the concentration of allyl-FL in PMMA could be increased to 4.5 wt% without decrease of the luminescence efficiency by adding the dendrimer into the system. The allyl-FL/dendrimer/PMMA film was embedded into a resonance cavity composed of two pieces of photonic band gap (PBG) materials to form a new-type solid-state laser. A laser emission at 589 nm was obtained when excited with a third harmonic generation (THG) of a pulsed Nd:YAG laser (355 nm) and its full-width at half-maximum of the spectrum was 1.7 nm.     

Investigation of patch antennas based on crossed idiosyncratic PBG structure

The method of finite difference time domain (FDTD) was used, and characteristics of the patch antenna based on drilling periodic air holes in the substrate were studied, the results indicate that the surface waves which propagate along the surface of the substrate can be suppressed by the crossed idiosyncratic PBG (photonic crystal band-gap) structure because of its effect of forbidden-band, that it can radiate most of electromagnetic waves’ energy in the substrate significantly, and that it has lower return loss (S11) compared to the conventional patch antennas, thus, a high gain is attained, its performance is improved. Due to these advantages, the use of photonic crystal patch antennas will be extended in areas such as mobile communication, satellite communication, aviation, etc.     

Design of 45-degree Linearly Polarized Substrate Integrated Waveguide-fed Slot Array Antennas

This paper presents a method of designing substrate integrated waveguide-fed (SIW-fed) slot array antennas. The design theory is based on the circuit model of slot and via as well as the reflection canceling. To prove the feasibility of this method, a 10-element K-band SIW-fed 45-degree linearly polarized slot array antenna with uniform power distribution is designed. By full-wave simulation, the antenna has a good impedance bandwidth of 7.5% and uniform power distribution. Besides, a maximum gain of 15.3dBi is obtained in the broadside and the cross polarization is suppressed below -23.5dB in the boresight. This type of SIW-fed slot array antennas can be a good candidate for microwave and millimeter-wave applications, especially for auto-motive collision-avoidance radar systems.     

Analysis of FSS with Dielectric Losses at Millimeter Wave Band Using the Transverse Transmission Line Method

The analysis of periodic structures on isotropic substrates with dielectric losses is presented. Frequency selective surface structures composed by an array of conducting patch elements are considered. This analysis uses the Galerkin method in combination with the transverse transmission line method, in the Fourier domain, to determine the reflection and transmission characteristics of the considered structures. The analysis provides very accurate results compared to those presented by other authors.     

有耗孤子的最小作用量原理及其在二维光子带隙结构中的应用

采用变分方法对于二维矩形光子带隙结构中X点孤子的耗散以及相干作用进行了动力学分析.通过对由作用量原理得到的孤子参量联立方程组的分析可知，除了耗散作用导致孤子的幅度衰减，并引起孤子横向的展宽以外，同向孤子的相互作用负势函数为耗散作用所减弱，从而使得孤子在x方向的束缚态被削弱.孤子中心间距随x的增加呈现出增幅变化且波动周期增大，当纵向距离增大到一定值后，孤子中心间距将一直增大下去.     

Assessment of Submarine Antennas for Millimeter-Wave Satellite Communication

This communication examines the theoretical basis for estimating the maximum gain of proposed millimeter-wave antenna systems when the space available for such antennas in the submarine mast is fixed. Limits derived in Harrington's classic paper are found to be applicable. The role of the gain-bandwidth product in assessing the system performance is also discussed.     

Investigations of Linearly Chirped Fiber Bragg Gratings for Time-Steered Array Antennas

The use of linearly chirped fiber Bragg gratings as dispersive delay line elements in optical true time-delay beamformers is investigated. Two different dispersive prism beamforming architectures are considered as is their impact on the grating specifications. Microwave double-sideband and single-sideband characterization is carried out on gratings suitable for both architectures with an emphasis on the group delay ripple of single and cascaded gratings. Results indicate that commercially available gratings are suitable for beamforming applications.     

Analysis of microring filter with two embedded microring

In this paper, a microring resonator with two embedded microring (MRTEM) has been presented and studied theoretically. Transfer matrix method (TMM) has been used to simulate MRTEM and analyze the relations between add/drop spectrum and embedded microring arrangements. Three kinds of embedded microring arrangements have been proposed and analyzed by TMM. The theoretical and simulation results show that the Q factor of our structure is higher than that of traditional microring structure and the spectrum of MRTEM is independent on embedded arrangements.     

Antennas for Short Distance Communications in Cryogenic Environment

Sets of bow-tie antennas, used in a single emitter-receiver near-field configuration and in array configuration, have been studied to be used as wireless means to transmit 8–12 GHz microwave signals from the cold stage of a cryogenic system to a room-temperature processing unit. Indeed, the absence of heat conduction allows increasing the performance of cryogenic systems and open the way to multichannel microwave systems that are necessary for imagers. Transmission loss has been found to be lower than 3 dB over a 1.5 GHz bandwidth while crosstalk in the array configuration is kept below −20 dB when antennas are located at around 90 mm transversally from each other.     

Genetic Algorithms for Design of Discrete Phase-only Reconfigurable Array Antennas with Fixed Dynamic Range Ratio

In this paper, we present a new method based on real-coded Genetic Algorithm (GA) with elitist model for optimal design of a reconfigurable symmetrical dual-beam uniformly spaced linear isotropic antenna array with phase-only control of quantized phase shifters. The problem is to find a common amplitude distribution that will generate a pencil beam with zero phases and a flat-top beam with discrete phases of a six-bit discrete phase shifter, without or with pre-fixing the value of dynamic range ratio (|I _max/I _min|) of excitation current amplitude distribution equal to or less than five.     

Unilateral Fin Line Directional Coupler

Photonic band gap (PBG) crystals have been used as a perfectly reflecting substrate for many millimeter wave applications. In this work the fin line directional coupler with substrate PBG was analyzed using the TTL - Transverse Transmission Line - method. Compared to other full wave methods the TTL is an efficient tool to determine the coupler characteristics, making possible a significant algebraic simplification of the equations involved in the process. In order to analyze this structure the effective dielectric constant, the attenuation constant and the coupling were determined. The results obtained for this application and the conclusions are presented. This work was partially financed by CNPQ.     

Investigations of Linearly Chirped Fiber Bragg Gratings for Time-Steered Array Antennas

The use of linearly chirped fiber Bragg gratings as dispersive delay line elements in optical true time-delay beamformers is investigated. Two different dispersive prism beamforming architectures are considered as is their impact on the grating specifications. Microwave double-sideband and single-sideband characterization is carried out on gratings suitable for both architectures with an emphasis on the group delay ripple of single and cascaded gratings. Results indicate that commercially available gratings are suitable for beamforming applications.     

The Use of the FDTD Method for Electromagnetic Analysis in the Presence of Indepedently Time-Varying Media

The suitability of the finite-difference time-domain (FDTD) method for electromagnetic modelling in the presence of independently-time-varying materials is investigated. Two examples are given and results compared to those obtained using other theoretical approaches.     

天线共振子理论对吡啶分子在铁钴镍衬底上SERS增强因子的计算

天线共振子模型是在研究表面增强拉曼散射增强机理过程中提出的理论.作为一项非常具有代表意义的工作,文章利用天线共振子模型计算了吡啶分子1010 cm-1特征振动模在过渡金属Fe,Co,Ni衬底上的表面增强拉曼散射增强因子:给出了共振时三种金属增强因子与激发光能量的依赖关系;研究了它们的表面粗糙度对增强因子的影响,计算了能量为0.89 eV的入射光在不同表面粗糙度的三种金属衬底上的增强因子.计算结果表明,它们在可见光范围增强因子不大,这与已报道的实验结果一致;但在红外波长却有大的增强因子,可以达到104～107,有待实验检验.     

Millimeter-wave Low Sidelobe Time Modulated Linear Arrays with Uniform Amplitude Excitations

The study of millimeter-wave low sidelobe linear arrays with time modulation technique is presented in this paper. Special emphasis is on the realization of low sidelobes with uniform amplitude excitations, which are easier for the practical implementation. Two types of time modulated linear arrays with uniform amplitude excitations, namely, the variable aperture size (VAS) linear arrays with optimized time sequences and the linear arrays with optimized random time sequences were studied. The optimized time sequences are obtained via the differential evolution (DE) algorithm and the genetic algorithm (GA). Many factors that affect the array performance are discussed. Supported by the National Natural Science Foundation of China (No. 60571023), the SRF for ROCS, SEM, and the innovative Research Team Program of UESTC, China.     

Metallization thickness in bilateral and unilateral Finlines

The theory and numerical results are presented to the effective dielectric constant and characteristic impedance of bilateral and unilateral finlines with metallization thickness. The full wave analysis of the transverse transmission line — TTL method is used to determine the electromagnetic fields of the structure in Fourier transform domain — FTD. Applying the suitable boundary conditions and the moment method, a homogeneous matrix system is obtained and the effective dielectric constant is extracted. The characteristic impedance is obtained using the relation between the voltage in slot and the transmitted power.Computational programs are developed to obtain numerical results to the effective dielectric constant and characteristic impedance.     

传输矩阵法分析微环谐振器阵列传输特性

微环谐振器可用作未来高密度、超大规模集成光路的基本构件,其重要发展方向之一是多环化、阵列化,微环谐振器阵列近来成为研究的热点。基于定向耦合器、环形谐振腔、直波导腔的基本单元传输矩阵,建立了用于分析微环谐振器阵列传输特性的传输矩阵模型。讨论了列间距对传输特性的影响,并数值模拟了不同尺度的奇数行和偶数行情况下谐振器阵列的传输特性。结合此传输矩阵模型,讨论了通过改变微环谐振器阵列的尺度以及耦合系数以实现滤波特性改善的方案。最后数值研究了最小尺度微环谐振器阵列传输特性与腔间耦合系数的关系。     

基于人工复合材料的太赫兹波双波段滤波

本文分别从实验和理论模拟两方面详细的讨论了金属双环和反双环两种亚波长阵列结构在太赫兹波段的双频率响应特性. 这两种双环结构都可以实现双频率调制,金属双环结构表现为两个明显的吸收峰,反双环结构则表现出明显的透过峰. 这两种结构不仅在物理结构上互补,在太赫兹波段的响应也表现为吸收和透过互补的特性. 其中高频响应来源于内环电子振荡,低频影响则来源于外环电子振荡,并且这种结构在太赫兹波段的响应与周期无关. 关键词： 太赫兹 滤波器 亚波长阵列 FDTD     

基于开环振荡器阵列磁振荡效应的全光开关

We demonstrate an all-optical switching of the magnetic resonance properties associated with a metallic Split Ring Resonator（SRR） array. The periodically spaced elements are fabricated on a high-resistivity silicon wafer and probed by using conventional Terahertz （THz） time-domain spectroscopy. We use a continuous-wave laser diode to generate carriers in the gaps of the SRR elements. Using a sufficient power, this opti- cal excitation can create an effective short gap, which would switch the resonant properties of the metamaterial from that of an SRR array to that of a closed ring resonator array and leads to dramatic changes in the THz transmission. In the present experiment, the optically induced switching is associated with the magnetic reso- nance. However, with appropriate changes in the device structure, this approach can be extended to switch a medium with a negative real index of refraction to a medium with a positive real index of refraction. This opens the way to creat a broad new range of active devices.