用频率分辨光学开关法测量飞秒激光脉冲

飞秒脉冲的测量在飞秒激光的应用中起着关键性作用.文中阐述了频率分辨光学开关法测量飞秒脉冲的原理和再现算法,构建了一台用于飞秒脉冲测量的二次谐波-频率分辨光学开关装置,利用该装置对谐振腔输出的飞秒脉冲进行了测量.利用二次谐波-频率分辨光学开关法测量得到了描迹图信号,对信号分布进行计算机迭代处理,得到了飞秒脉冲的时间宽度及光谱宽度、电场及其位相在时域和频域的详细信息.谐振腔直接输出脉冲的时间宽度为56 fs,光谱宽度为27 am,时间带宽积为0.686,算法中的最小误差为0.001 792.实验结果表明二次谐波.频率分辨光学开关法是一种有效的飞秒脉冲测量方法.     

电力谐波实验台研究与设计

电力谐波实验台是一种通过模拟实际电网中产生的谐波电流并对其进行实时抑制的实验装置。该实验装置采用公共基础台+功能挂件的设计方式,结构紧凑,集成度高,扩展性好,能够完成电力谐波的产生、在线检测、分析、有源滤波等多项实验。装置软件实现由DSP控制器和上位机两部分组成。DSP控制器采用自适应滤波理论的单神经元电力谐波动态检测算法和滞环控制算法实现系统的补偿。上位机负责计量、监测、显示、储存等功能,是实验装置虚拟仪器的核心部分。该装置系统具有较高的教学使用和科研价值。     

实时在线谐波检测装置的设计与实现

为便于实时监测谐波和加强谐波管理,针对电力系统谐波的特点,本文提出一种实时在线谐波检测装置的设计与实现方法。用89C51实现整个检测过程,满足实时在线检测的要求。对于谐波检测过程中的频谱混叠和频谱泄漏问题,这里采用滤波器和自适应算法提高谐波检测的精度。同时利用虚拟仪器技术,设计出良好的用户界面。实验证明,该装置具有高精度,高性价比等优点。     

基于遗传算法的复杂背景噪声中二维谐波的二次耦合分析

本文利用二维循环统计量方法对乘性噪声之间相关,乘性噪声和加性噪声之间也相关这种复杂噪声背景中二维谐波的二次非线性耦合问题做了分析。利用当且仅当二维谐波中存在二次非线性耦合谐波时,所定义的二维三阶时间平均矩谱仅在参与二次耦合谐波频率处取得极值的性质,提出了采用遗传算法来分析二维谐波的：二次非线性耦合问题的算法。仿真实验证明了算法的有效性。     

高次谐波辐射的实验研究

报道了在本实验室建立的45fs-2 TW级超短超强钛宝石激光装置上.以Ar为非线性工作介质.进行的高次谐波实验的初步研究结果.初步研究了激光能量和气体密度对高次谐波的影响,目前得到的最高次谐波为第25次谐波.相应波长为31.4nm.还检验了激光器、压电气阀、光谱仪以及信号处理和记录系统的工作性能.实现了相互间的协调.     

二次谐波信号降噪方法的研究

在近红外区域，利用波长调制光谱技术进行气体浓度检测时，光学元件以及电子器件的噪声会影响二次谐波信号的信噪比。为了抑制噪声，提出一种基于经验模态分解、去趋势波动分析和小波自适应阈值的复合降噪算法。该算法针对传统经验模态分解降噪算法中存在的有用信号缺失的问题，利用去趋势波动分析优化对于信息主导本征模函数的筛选，将筛选出的信息主导本征模函数进行信号重构，再用小波自适应阈值算法提高降噪精度。将提出的算法与经典的降噪算法进行对比评估，提出的算法降噪后的二次谐波信号与原二次谐波信号的互相关系数为99.9018%，均方根误差为0.0087%。通过对实验中实际得到的二次谐波信号进行去噪，结果表明提出的算法去噪效果明显，能够保留有用的信息点。     

大型望远镜拼接弧线永磁电机电流谐波抑制

望远镜口径的增加使得其轴系驱动电机越来越大,近年来拼接电机成为国际上研究的热点.拼接弧线永磁电机的电流谐波影响大型天文望远镜目标观测轴系跟踪精度,文中根据拼接弧线电机的数学模型及谐波分析,提出了一种基于准比例-谐振控制器的电流谐波抑制算法,并设计了单元拼接弧线电机相应的电流控制器.仿真和实验分别对比了PI和准比例谐振控制器对电流谐波的影响.实验结果表明,采用准比例谐振控制器时,拼接弧线电机定子电流中的5次谐波分量削弱了63.3％,7次谐波分量削弱了34.4％,11次谐波分量削弱了51％,13次谐波分量削弱了59.2％,大大降低了拼接弧线电机电流谐波,有助于提高望远镜跟踪精度.     

基于Hamilton四元数矩阵奇异值分解的二维谐波频率参量估计

对于二维谐波信号的四元数模型,首先论述其与二维谐波的实数模型和复数模型之间的对应与转换关系,之后提出运用四元数矩阵奇异值分解估计二维谐波中频率参量的算法.这种算法首先可以利用四元数矩阵的奇异值判断出原始的二维谐波信号个数,然后再分别利用四元数矩阵的左、右奇异向量中的噪声向量构造的噪声子空间估计出两维的谐波频率参量.算法本身需要的数据量少,数据矩阵构造简单,并且可以同时估计出两维谐波频率参量.从仿真实验中可以看出,本文提出的算法计算量相对其它针对二维谐波四元数模型的算法要小.仿真实验验证了本文算法的正确性.     

基于FFT与DWT联合的电力谐波检测的算法设计

目前谐波检测方法普遍存在的问题是很难对稳态谐波和非稳态谐波同时存在的信号进行准确检测.针对这种现象本文提出了一种混合算法:利用DWT将谐波信号成分低频和高频两部分;FFT对低频部分进行分析,得出稳态谐波的幅值、相位;小波熵对高频部分进行分析,得到非稳态谐波的时域信息.该算法结合以上算法的优势,完成对稳态谐波和非稳态谐波同时存在的信号的检测.并通过MATLAB验证该算法的准确性和可行性.     

谐波发生装置的技术原理和设计

文章设计采用了以DSP TMS320F2812芯片为核心的谐波发生装置,利用谐波无功模拟系统可同时发生2~50次谐波,可选择特定次数谐波发生,各次谐波独立可调,并且利用谐波变压器可在400V、690V、800V和1200V之间来回切换。文中主要介绍了系统结构、主电路技术和控制回路。最后实验调试结果表明系统稳定可靠,满足实际检测要求。     

An Active-Inductor Injection Locked Frequency Divider With Variable Division Ratio

This letter presents a wide-locking range, body-injected, injection locked frequency divider (ILFD) with tunable active inductors (TAIs) and variable division ratio. The ILFD was fabricated in the 0.18 mum 1P6M CMOS technology, and it has the modulus of 2, 3, 4, and 5, and can be used as a first-harmonic injection-locked oscillator (ILO). The divide-by-3 function is performed by injecting differential a signal to the bodies of cross-coupled transistors in the VCO. At the supply voltage of 1.5 V, the free-running divider is tunable from 0.53 to 1.72 GHz. At the incident power of 0 dBm the operation range in the first-harmonic ILO is from the incident frequency 0.53 to 3.2 GHz. The operation range in the divide-by-3 (divide-by-2) mode is about 3.59 (4.13) GHz, from the incident frequency 1.55 to 5.14 (0.87 to 5.0) GHz.     

Efficiency optimization in ZVS series resonant inverters with asymmetrical voltage-cancellation control

This paper presents a time-domain analysis and a computerized search algorithm for optimizing the efficiency in zero-voltage switching (ZVS) full-bridge series resonant inverters with asymmetrical voltage-cancellation (AVC) control for different load quality factors. The optimum AVC control found allows all the switches to be turned on with zero voltage with the minimum switching frequency. In order to minimize losses, the switching frequency is kept as close as possible to resonance. The optimum AVC control is compared with previous fixed or narrow frequency range control strategies to show that it improves performance over all the output power range for different loads. The detailed steady-state analysis carried out here increases the precision of the first-harmonic analysis of a previous work, which is especially important with distorted output currents due to low load quality factors or highly asymmetrical modulation strategies. The theoretical results are verified experimentally.     

激光外差干涉检偏器旋转误差对非线性误差的影响

为了减小激光外差干涉纳米测量的非线性误差,必须明确检偏器旋转误差对非线性误差的影响机理与消除方法。通过分析激光外差干涉检偏器旋转误差对非线性误差的影响,推导出检偏器旋转误差对非线性误差一次谐波和二次谐波的影响模型。仿真结果表明,当存在激光束椭圆偏振时,检偏器旋转误差对非线性误差的影响很小;当存在偏振分光镜旋转误差时,检偏器旋转误差引起的非线性误差不增加二次谐波分量,但增大了非线性误差一次谐波分量,严重影响非线性误差的大小,当偏振分光镜旋转误差为3°时,检偏器旋转误差从0°增加到5°,非线性误差从0.14 nm增大到0.97 nm。     

偏振分光镜分光性能非理想对激光外差干涉非线性误差的影响

为了减小激光外差干涉纳米测量的非线性误差,必须明确偏振分光镜(PBS)分光性能非理想对非线性误差的影响机制.推导出非理想情况下偏振分光镜透射率和反射率的激光外差干涉非线性误差模型,建立了偏振分光镜分光性能非理想对非线性误差二次谐波的影响模型.仿真结果表明,偏振分光镜的透射率和反射率非理想对非线性误差的影响为一次谐波,且偏振分光镜分光性能越差,其对非线性误差的影响也越大.在偏振分光镜反射率为0.90的情况下,偏振分光镜透射率从1减小到0.90时,非线性误差由0.62 nm增大到1.24 nm.当存在偏振分光镜旋转角度误差时,偏振分光镜分光性能非理想引起的非线性误差不增加二次谐波分量,但增大了非线性误差一次谐波分量,严重影响非线性误差的大小.当偏振分光镜旋转角度误差为5°时,偏振分光镜透射率从1变为0.90,非线性误差从0.39 nm增大到1.41 nm.     

First- and second-harmonic radiations from a near-millimeter-wave gyromonotron

First- and second-harmonic radiations in frequency regions centered around 120 and 240 GHz, respectively, have been observed from a gyromonotron employing magnetic fields between 34 and 54 kG and a magnetron injection gun preducing a 30-kV, 1- to 2-A electron beam. Extensive redesign of the cavity, electron beam tunnel holders, and vacuum envelope resulted in greatly improved tube performance over that obtained previously. Nine first-harmonic modes and three second-harmonic modes were identified with specific TE cavity modes. These identifications were based on agreement between the measured frequency of a radiation and the calculated resonant frequency of a TE mode, and one or both of the following: (a) the agreement between the magnetic field at which the radiation occurred and that predicted by linear theory calculations of threshold current versus magnetic field for that mode; and (b) the similarity between the far-field antenna pattern measured with calibrated, waveguide-mounted detectors and that predicted for that mode. Output power was measured with a Scientech 362 Calorimeter and also estimated by integrating the far-field antenna patterns measured with the calibrated detectors. The power ranged from a fraction of a watt to 200 W for second-harmonic modes, and from tens of watts to 2 kW for first-harmonic modes.     

一种激光外差干涉非线性误差新颖测量方法

为了精确测量激光外差干涉非线性误差,提出了一种新的激光外差干涉非线性误差测量方法。通过对来自激光外差干涉测量臂的输出信号直接进行数据采集和频谱分析,分离出非线性误差的一次谐波和二次谐波分量,得到非线性误差相对测量信号之间的幅度比值;通过建立激光外差干涉非线性误差与幅度比值之间的模型,实现对激光外差干涉非线性误差的精确测量。实验结果表明,应用非线性幅度模型和频谱分析的方法能够精确地测量激光外差干涉非线性误差,相对其它测量方法具有结构简单、易于实现、避免传感器引入非线性误差等优点。     

Radar surface signatures based on the two-dimensional tidalcirculation of Phelps Bank

Numerical results for the M₂ tidal currents over Phelps Bank, Nantucket Shoals, Massachusetts, with 1/8×1/8 min arc resolution are used to predict the radar surface signatures (cross sections σ) of Phelps Bank using the first-order relaxation model of W. Alpers and I. Hennings (1984). The numerical predictions of σ incorporate all two-dimensional contributions from the tidal currents and include both the residual and first-harmonic term. Strong correlation between spatially resolved contour plots of σ over a wide range of directions and time intervals within the tidal cycle, with variations in the bottom topography of the Phelps Bank, is obtained even when Bragg wave scattering alone is included. The predictions for σ are contrasted with previous measurements in the Phelps Bank by the US Naval Research Laboratory, and the importance of including the off-diagonal elements from the current stress tensor in the evaluation of σ is discussed     

CMOS Quadrature VCO Implemented With Two First-Harmonic Injection-Locked Oscillators

This letter presents a new quadrature voltage-controlled oscillator (QVCO). The LC-tank QVCO consists of two first-harmonic injection-locked oscillators (ILOs). The outputs of one ILO are injected to the gates of the tail transistors on the other ILO and vice versa so as to force the two ILOs operate in quadrature. The proposed CMOS QVCO has been implemented with the TSMC 0.18 mum CMOS technology and the die area is 0.582 times 0.972 mm². At the supply voltage of 1.0 V, the total power consumption is 8.0 mW. The free-running frequency of the QVCO is tunable from 5.31 GHz to 5.75 GHz as the tuning voltage is varied from 0.0 V to 1.0 V. The measured phase noise at 1 MHz offset is -120.01 dBc/Hz at the oscillation frequency of 5.31 GHz and the figure of merit (FOM) of the proposed QVCO is about -185.48 dBc/Hz.     

A method of analysis of periodic processes in nonautonomous discrete-time systems with quantization

A method of analysis of stationary processes in systems with an arbitrary number of quantization levels in the presence of periodic external signals is proposed. The method is based on the representation of stationary oscillations in the form of an invariant set of nonlinear discrete point mappings. The spectral composition of the response of a system with an arbitrary period coupled with the discretization period through a rational relationship is calculated with the use of the discrete Fourier transform. The discrete Fourier transform is applied also to calculate nonlinear distortions. It is suggested to use the dependence of the ratio of the first-harmonic amplitude of the system’s steady-state response to the amplitude of the input-signal harmonic on the frequency of the input harmonic signal as the amplitude-frequency characteristic of a nonlinear system. In addition, it is suggested to use the dependence of the difference between the argument of the first harmonic of the system’s response and the initial phase of the input signal on the frequency of the input harmonic signal as the phase-frequency characteristic of the system. The usage of the method is illustrated by its application for the analysis of processes in first-and second-order circuits.     

Multi-Modulus LC Injection-Locked Frequency Dividers Using Single-Ended Injection

A new wide-locking range multi-modulus LC-tank injection locked frequency divider (ILFD) is proposed and was fabricated in a 0.18 $mu {rm m}$ CMOS process. The ILFD circuit is realized with a complementary MOS LC-tank oscillator and an injection composite composed of an inductor in series with an injection MOS. The two output terminals of the injection composite are connected to the resonator outputs. The ILFD can be used as a first-harmonic oscillator (ILO), even-modulo or odd-modulo oscillator depending upon the incident frequency of injection signal. At the supply voltage of 1.5 V, the free-running frequency is from 4.85 to 5.13 GHz, the current and power consumption of the divider without buffers are 2.78 and 4.17 mW, respectively. At the incident power of 0 dBm, the locking range in the divide-by-1(2, 3, 4) mode is from the incident frequency 3.72 to 8.69 (8.42 to 10.95, 13.66 to 16.03, 19.13 to 20.5) GHz.