Low conversion-loss fourth subharmonic mixers incorporating CMRC for millimeter-wave applications

Low conversion-loss millimeter-wave fourth subharmonic (SH) mixer designs are proposed in this paper. A millimeter-wave (35 GHz) fourth SH mixer with four open/shorted stubs is designed and measured. The conversion loss is less than 15 dB within a 2.4-GHz bandwidth. The minimum loss is 11.5 dB at the center frequency. By replacing two of the shunt stubs with a dual-frequency in-line stub consisting of newly developed compact microstrip resonating cells (CMRCs), the performance of the SH mixer is improved significantly. At 35 GHz, the conversion loss of this new fourth SH mixer is as low as 6.1 dB with a 3-dB bandwidth of 6 GHz. The conversion loss in the whole Ka-band (26.5-40 GHz) is less than 16 dB. The proposed fourth SH mixer incorporating with CMRCs provides a low-cost high-performance solution for RF subsystem design.     

一种5阶1位∑-△调制器的设计

提出了一种稳定的5阶∑-△调制器的设计与调试方法.电路采用5阶级联结构,主要用CMOS开关电容技术实现,文章重点放在调制器结构的设计及几种防止系统发散和改进性能的途径上.模拟实验表明,经过改进的系统有较好的性能.     

专注安全,追求卓越--西安安智科技有限公司

随着Internet的发展,信息安全问 题日益严重,面对客户的迫切需求, 西安安智科技有限公司对依赖网络获 得战略性收益的客户一直给予了密切 的关注。通过对网络安全性、网络性 能及网络经济进行彻底的变革来帮助 客户实现他们的目标,为他们的企业 创建竞争优势。 安智科技按照 ISO9001 和CMM 管理规范的要求,对产品需求、研发、 生产等各环节进行了严格控制,充分 保证产品品质,为用户构建更安全的 信息环境提供了坚实的基础,也为公 司的渠道合作伙伴创造了更多的发展 空间。通过提供一系列全面、灵活、业 界领先的技术支持、专业服务以及…     

凹槽栅场板结构的AlGaN/GaN HEMT特性分析

研究了无场调制板结构、有场调制板结构但无凹槽栅、结合场调制板结构和凹槽栅工艺三种AlGaN/GaN HEMT的动态I-V特性和微波特性,认为场调制板结构和凹槽栅工艺可以有效改善AlGaN/GaN HEMT器件沟道内电场分布,显著减小电流崩塌现象,提高器件的微波输出功率特性.利用此技术研制的1mm栅宽AlGaN/GaNHEMT输出功率大于10W.     

Testing for statistical significance in bispectra: a surrogate data approach and application to neuroscience

Interactions among neural signals in different frequency bands have become a focus of strong interest in neuroscience. Bispectral analysis, a type of higher order spectral analysis, provides us with the ability to investigate such nonlinear interactions. Based on the fact that the bispectrum of a linear Gaussian process is zero, a surrogate data method was proposed to test the null hypothesis that the original data were generated by a linear Gaussian process. The method was first tested on two simulation examples. It was then applied to local field potential recordings from a monkey performing a visuomotor task. The analysis reveals nonzero bispectra for beta and gamma band activities in the premotor cortex. The rigorous statistical framework proves essential in establishing these results.     

Energy-efficient power allocation for NOMA heterogeneous networks with imperfect CSI

In this paper, an optimal user power allocation scheme is proposed to maximize the energy efficiency for downlink non-orthogonal multiple access (NOMA) heterogeneous networks (HetNets). Considering channel estimation errors and inter-user interference under imperfect channel state information (CSI), the energy efficiency optimization problem is formulated, which is non-deterministic polynomial (NP)-hard and non-convex. To cope with this intractable problem, the optimization problem is converted into a convex problem and address it by the Lagrangian dual method. However, it is difficult to obtain closed-form solutions since the variables are coupled with each other. Therefore, a Lagrangian and sub-gradient based algorithm is proposed. In the inner layer loop, optimal powers are derived by the sub-gradient method. In the outer layer loop, optimal Lagrangian dual variables are obtained. Simulation results show that the proposed algorithm can significantly improve energy efficiency compared with traditional power allocation algorithms.     

Novel oscillator incorporating a compact microstrip resonant cell

A novel transistor oscillator incorporating a compact microstrip resonant cell (CMRC) as its terminating resonance is proposed. Adjusting the dimensions of the cell, it is possible that the fundamental frequency can be positively fed back and the second harmonic negatively fed back at the input port of the oscillator. The fundamental output is enhanced with the second harmonic being suppressed. The output power of the proposed CMRC oscillator is 14.7 dBm at 2.5 GHz with 27.1 dB rejection of the second harmonic, outperforming the conventional microstrip termination with a 40% size reduction     

Effect of concentration of cadmium sulfate solution on structural,optical and electric properties of Cd1-xZnxS thin films

Cd1-xZnxS thin films were deposited by chemical bath deposition(CBD)on the glass substrate to study the influence of cadmium sulfate concentration on the structural characteristics of the thin film.The SEM results show that the thin film sur-faces under the cadmium sulfate concentration of 0.005 M exhibit better compactness and uniformity.The distribution dia-grams of thin film elements illustrate the film growth rate changes on the trend of the increase,decrease,and increase with the increase of cadmium sulfate concentration.XRD studies exhibit the crystal structure of the film is the hexagonal phase,and there are obvious diffraction peaks and better crystallinity when the concentration is 0.005 M.Spectrophotometer test results demonstrate that the relationship between zinc content x and optical band gap value Eg can be expressed by the equation Eg(x)=0.59x2+0.69x+2.43.Increasing the zinc content can increase the optical band gap,and the absorbance of the thin film can be improved by decreasing the cadmium sulfate concentration,however,all of them have good transmittance.At a concen-tration of 0.005 M,the thin film has good absorbance in the 300-800 nm range,80％transmittance,and band gap value of 3.24 eV,which is suitable for use as a buffer layer for solar cells.     

Engineered Elastomer Substrates for Guided Assembly of Complex 3D Mesostructures by Spatially Nonuniform Compressive Buckling

Approaches capable of creating 3D mesostructures in advanced materials (device‐grade semiconductors, electroactive polymers, etc.) are of increasing interest in modern materials research. A versatile set of approaches exploits transformation of planar precursors into 3D architectures through the action of compressive forces associated with release of prestrain in a supporting elastomer substrate. Although a diverse set of 3D structures can be realized in nearly any class of material in this way, all previously reported demonstrations lack the ability to vary the degree of compression imparted to different regions of the 2D precursor, thus constraining the diversity of 3D geometries. This paper presents a set of ideas in materials and mechanics in which elastomeric substrates with engineered distributions of thickness yield desired strain distributions for targeted control over resultant 3D mesostructures geometries. This approach is compatible with a broad range of advanced functional materials from device‐grade semiconductors to commercially available thin films, over length scales from tens of micrometers to several millimeters. A wide range of 3D structures can be produced in this way, some of which have direct relevance to applications in tunable optics and stretchable electronics.     

光子吸收诱导无序技术的光荧光谱研究

运用 1 0 6 4μm连续输出的Nd∶YAG激光器 ,对与InP晶格匹配的InGaAsP四元系量子阱材料进行了光子吸收诱导无序 (PAID)技术的研究。通过光荧光谱 (PL)的测量 ,证明有量子阱混合现象产生。衬底预加热和聚焦激光束结果表明 ,PAID中辐照时间与衬底温度、辐照的平均功率密度密切相关。聚焦激光照射后的荧光双峰表明PAID有一定的定域处理能力。