PSS4B型电力系统稳定器参数整定

PSS4B是一种新型的多频段电力系统稳定器,因能同时抑制多个振荡模式且设置更加灵活而具有广泛的应用前景,但PSS4B参数整定相对复杂,目前相关的研究还比较少。按实际应用要求,在系统多运行方式下,用相位补偿法整定超前滞后环节的时间常数,用根轨迹法确定增益;在概率特征根分析的基础上,部分计及PSS相互间的影响,使用概率灵敏度分析法进行分析。由此进行的PSS4B参数整定,将使PSS4B在多运行方式下充分发挥优势。在一8机24节点系统上进行分析,结果表明安装的6台PSS4B均能提供对关注的振荡模式的有效阻尼,具有较强的适应性和通用性。     

改进语音增强多频带谱减算法研究

针对传统谱减语音增强算法增强后的语音信号会残留明显的"音乐噪声"的问题,采用多频带谱减算法对其进行改进。改进算法的原理是将带噪的语音信号按照频率划分成不同的频带,并使这些频带之间互不交叠,根据频带内带有噪声的语音信号和噪声信号信噪比,利用自适应算法求得该频带的过减因子。仿真结果表明:改进多频带谱减算法的语音增强效果优于传统谱减法。     

Fully integrated low phase noise multi-band LC-tank voltage controlled oscillator with switched-capacitor resonator

This paper presents the design and implementation of a fully integrated low noise multi-band LC-tank voltage-controlled-oscillator(VCO).Multi-band operation is achieved by using switched-capacitor resonator.Additional three-bit binary weighted capacitor array is also used to extend frequency tuning range in each band.To lower phase noise,two noise filters are added and a linear varactor is adopted.Implemented in a 0.18 μm complementary-metal-oxide-semiconductor(CMOS) process,the VCO achieves a frequency tuning range covering 2.26～2.48 GHz,2.48～2.78 GHz,2.94～3.38 GHz,and 3.45～4.23 GHz while occupies a chip area of 0.52 mm2.With a 1.8 V power supply,it draws a current of 10.9 mA,10.6 mA,8.8 mA,and 6.2 mA from the lowest band to the highest band respectively.The measured phase noise is-109～-120 dBc/Hz and-121～-131 dBc/Hz at a 1 MHz and 2.5 MHz offset from the carrier,respectively.     

基于Walsh函数的多电平逆变器多波段SHEPWM控制技术

基于Walsh函数变换的特定谐波消除脉宽调制(selected harmonics elimination pulse width modulation,SHEPWM)技术存在调制比受限的问题,为此,提出了基于Walsh函数的多电平逆变器多波段SHEPWM控制技术。该方法通过分析傅里叶级数变换下的多电平多波段SHEPWM电压波形,归纳出调制比从0到1之间变化时多电平逆变器多波段统一的SHEPWM非线性方程组,再利用Walsh函数变换对其进行求解,从而同时解决了拓展调制比、在线计算、实时控制的难题。以7电平为例,给出了各个波段下的Walsh函数分段线性方程组及开关角度轨迹,同时还考虑了调制比切换处多组解的情况。算例结果验证了该方法的可行性。     

On the design of CPW-feed diamond shape fractal antenna for UWB applications

This article presents the design of diamond shape fractal antenna with coplanar waveguide feed for ultra-wide bandwidth. This new fractal antenna has been designed on substrate ε_r ?=?4.3 and thickness h?=?1.53?mm. The antenna has been constructed incorporating fractal geometry in a circular disc of 30?mm diameter. The experimental result of this proposed antenna exhibits the excellent ultra-wide bandwidth from 2.05?GHz to 6.245?GHz. The detail parametric studies have been carried out using electromagnetic simulator HFSS10. The experimental results are in close agreement with the simulated results. The experimental radiation patterns are nearly omni-directional in H-plane and dumble shape in the E-plane throughout the frequency band of interest. The measured group delay of this antenna is stable throughout the band. Such type of antenna is useful for ultra-wideband communication system, microwave imaging and precision positioning system.     

一款用于数字电视调谐器的高线性度多频带增益可调信道选择滤波器

This paper presents a channel-select filter that employs an active-RC bi-quad structure for TV-tuner application. A design method to optimize the IIP3 of the bi-quad is developed. Multi-band selection and gain adjustment are implemented using switching resistors in the resistor array and capacitors in the capacitor array. Q-factor degradation is compensated by a tuning segmented resistor. A feed-forward OTA with high gain and low third-order distortion is applied in the bi-quad to maximize linearity performance and minimize area by avoiding extra compensation capacitor use. An RC tuning circuit and DC offset cancellation circuit are designed to overcome the process variation and DC offset, respectively. The experimental results yield an in-band IIP3 of more than 31 dBm at 0 dB gain, a 54 dB gain range with 6 dB gain step, and a continuous frequency tuning range from 0.25 to 4 MHz. The in-band ripple is less than 1.4 dB at high gain mode, while the gain error and frequency tuning error are no more than 3.4% and 5%, respectively. The design, which is fabricated in a 0.18 μm CMOS process, consumes 12.6 mW power at a 1.8 V supply and occupies 1.28 mm2.     

基于多进制扩频的低压电力线抄表技术的研究

低压电力线通信广泛应用于电力抄表系统中。由于低压电力线信道特性复杂,严重影响载波通信质量,结合相关数据资料对低压电力线信道噪声环境进行了分析。为了提高电力线信道条件下的传输可靠性,提出多进制扩频技术,构造了多进制伪随机序列。设计了多进制扩频的低压电力线抄表方案,并建立了基于该信道特性的电力线扩频通信系统模型。通过对其性能仿真验证,仿真结果表明:该多进制扩频方式有效改善了抄表系统误码率性能,更适合于电力线的抄表作业。     

大能量多波段皮秒激光技术研究

针对大能量多波段皮秒激光器的技术要求,提出了采用新型无独立单选模块再生放大技术,研究和分析了高功率密度下大能量激光放大系统的抗激光损伤技术、高效倍频、和频及四倍频技术。在重复频率10 Hz时,实现1064μnm输出单脉冲能量239.8 mJ,放大倍数达到108倍,峰值功率密度为40 GW/cm2以上。     

多波段图像融合算法研究及其新发展(Ⅱ)

对多通道、特别针对可见光与长波红外图像像素级融合的各种算法进行了深入的研究,针对工作实际需要,对其均进行了一定的改造和编程调试,对某些算法做了较重大改进,在若干方面提出了自己的具有特色的算法与思想。在此基础上编制了大型程序软件包。     

ICI mitigation in concurrent multi-band receiver due to the phase noise and IQ imbalance

This paper discusses control of chaos from an artificial neural cell. The cell is piecewise linear and includes bipolar hysteresis. A periodic stimulation switches the action potential represented by oscillation frequency and causes chaotic response. Using a mapping procedure, we can prove chaos generation and calculate the initial point of unstable periodic orbits (UPO) embedded in chaos. Then we can stabilize the desired UPO by using a modified occasional proportional feedback (OPF) which is applied only if the state is in a linear region and must stabilize the desired UPO in a theoretical sense. This OPF function is verified by laboratory experiments.