融资融券交易与A股市场波动相关性实证研究

本文基于A股市场开展融资融券交易以来的实际数据,用Johnson协整检验,误差修正模型和Granger因果关系检验方法,实证研究了融资融券业务的开展对A股市场价格和波动性的影响,结果显示融资融券交易对A股市场的价格和波动性的影响都不显著.     

基于ADF4107的锁相环仿真

本文根据锁相环的设计原理,基于锁相芯片ADF4107,利用AD公司的ADIsimPLL软件对锁相环外围电路进行了仿真,得到环路滤波器中的各个元件值,并利用其值,进行了实际的电路设计和制作,测试结果显示锁相环频率合成器工作性能良好。     

基于ADF4193的UHF频率合成器设计

频率合成芯片ADF4193具有小数分频和快速锁定特性。换频时通过增加电荷泵电流以扩大环路带宽,缩短了环路的锁定时间,并采用可编程开关调整环路元件参数来确保环路稳定。UHF跳频频率合成器以ADF4193为核心电路实现设计,采用ADIsimPLL软件仿真环路参数,利用低噪声运算放大器构成的电压放大器来扩大VCO的调谐电压范围,通过调整环路带宽及设计合理的PCB布局来抑制杂散,给出了实测结果。     

基于Σ-Δ调制技术的小数分频锁相环的应用

介绍了基于Σ-Δ调制技术的小数分频的锁相环是怎样降低输出杂散的。正是因为基于Σ-Δ调制技术的小数分频与传统小数分频相比具有较低的输出杂散,应用前景广阔。通过实例分析说明在设计频率综合器时,采用小数分频替代整数分频,以达到改善相位噪声的目的。为了实现小步进,通常采用DDS+PLL,在对频率转换时间要求不高的情况,也可以用小数分频来替代。     

使用Nios Ⅱ嵌入式软核CPU配置快速锁定锁相环频率合成芯片ADF4193

介绍了锁相环的原理和ADF4193芯片的特点和配置方式,结合Altera的SOPC技术,利用SOPC Builder中集成的SPI核,设计了一种基于Nios II软核CPU的嵌入式系统,用来配置AD公司生产的快锁芯片ADF4193。实测结果表明,配置成功。并且经过适当修改可用于其他基于SPI串口配置的芯片。     

D频段雷达传感器测距装置

针对其他各类传感器在极限条件下测距的局限性及微波雷达的全天候工作特点,提出了一种基于调频连续波(FMCW)工作方式的低功耗雷达测距装置。该装置功耗为500 mW,以120 GHz毫米波雷达传感器芯片为核心,使用STM32芯片进行控制及信号处理,基于ADF4169芯片完成所需的调频源输出。在对弱差频信号作滤波、放大、采集及频域处理后,通过上位机进行距离显示。实验结果表明:在1.5 m的单目标距离测试范围内,测距精度为3 cm。该系统的研究对推进D频段雷达传感器的实际应用具有重要价值。     

一种2～4GHz宽带接收机的小型化前端设计

针对2~4 GHz的超宽频带,提出了一种宽带接收机的前端设计方法,其中包括射频信道设计、频率合成器的设计以及基带电路设计。鉴于小型化的设计思想,射频前端采用零中频接收机的架构,使用LTCC滤波器实现噪声系数优于8 d B,输出三阶截断点优于27 d Bm(低噪声模式下)。频率合成器采用集成VCO的锁相环芯片ADF4351,实现单边带相位噪声优于-110 d Bc/Hz@200 k Hz。基带电路采用正交解调器ADL5380和12位双通道AD转换器AD9238,可实现带宽为20 MHz的I/Q双路同时解调。通过FPGA或DSP处理,可广泛用于便携式小型化的监测接收机或通信接收机。     

A flexible implementation of frozen-density embedding for use in multilevel simulations

A new implementation of frozen-density embedding (FDE) in the Amsterdam Density Functional (ADF) program package is presented. FDE is based on a subsystem formulation of density-functional theory (DFT), in which a large system is assembled from an arbitrary number of subsystems, which are coupled by an effective embedding potential. The new implementation allows both an optimization of all subsystems as a linear-scaling alternative to a conventional DFT treatment, the calculation of one active fragment in the presence of a frozen environment, and intermediate setups, in which individual subsystems are fully optimized, partially optimized, or completely frozen. It is shown how this flexible setup can facilitate the application of FDE in multilevel simulations.     

Chemistry with ADF

We present the theoretical and technical foundations of the Amsterdam Density Functional (ADF) program with a survey of the characteristics of the code (numerical integration, density fitting for the Coulomb potential, and STO basis functions). Recent developments enhance the efficiency of ADF (e.g., parallelization, near order‐N scaling, QM/MM) and its functionality (e.g., NMR chemical shifts, COSMO solvent effects, ZORA relativistic method, excitation energies, frequency‐dependent (hyper)polarizabilities, atomic VDD charges). In the Applications section we discuss the physical model of the electronic structure and the chemical bond, i.e., the Kohn–Sham molecular orbital (MO) theory, and illustrate the power of the Kohn–Sham MO model in conjunction with the ADF‐typical fragment approach to quantitatively understand and predict chemical phenomena. We review the “Activation‐strain TS interaction” (ATS) model of chemical reactivity as a conceptual framework for understanding how activation barriers of various types of (competing) reaction mechanisms arise and how they may be controlled, for example, in organic chemistry or homogeneous catalysis. Finally, we include a brief discussion of exemplary applications in the field of biochemistry (structure and bonding of DNA) and of time‐dependent density functional theory (TDDFT) to indicate how this development further reinforces the ADF tools for the analysis of chemical phenomena. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 931–967, 2001     

The Becke Fuzzy Cells Integration Scheme in the Amsterdam Density Functional Program Suite

In this article, we document a new implementation of the fuzzy cells scheme for numerical integration in polyatomic systems [Becke, J. Chem. Phys. 1998, 88, 2547] and compare its efficiency and accuracy with respect to an integration scheme based on the Voronoi space partitioning. We show that the accuracy of both methods is comparable, but that the fuzzy cells scheme is better suited for geometry optimization. For this method, we also introduce the locally dense grid concept and present a proof‐of‐concept application. © 2013 Wiley Periodicals, Inc.