太赫兹功率探测器高灵敏度调制解调系统设计

针对太赫兹被动成像系统前端功率探测器内部引入的低频噪声（1/f噪声）对成像精度的影响较为明显的问题,设计了一种高灵敏度调制解调系统来降低低频噪声对成像的干扰。通过控制外部信号源使功率探测器在正常工作与饱和状态之间快速切换,实现对目标信号的调制,从而将目标信号的频率调制到高于功率探测器引入的低频噪声频段以便将低频噪声滤除,进而降低该低频噪声对后续成像质量的影响。通过MATLAB软件仿真,可模拟出信噪比(SNR)为31.17 dB的功率探测器输出信号,同时通过对目标信号调制解调,目标信号的信噪比被提高到了268.13 dB。通过对所设计的高灵敏度调制解调系统实际测试,可得目标信号的信噪比由4.22 dB提高到了301.88 dB。研究结果表明,该高灵敏度调制解调系统能有效降低太赫兹探测器内引入的低频噪声对后续成像质量的影响。     

微弱正弦信号的全频域检测方法

基于变型蔡氏电路模型的锁频功能,将被检测信号作为变容二极管的调制信号的一部分,实现了对微弱正弦信号的检测.用四阶龙格-库塔方法对系统相变与调制信号的关系进行了数值实验,发现调制信号频率与系统相变之间存在周期关系,利用这种周期关系,可以实现全频域信号检测.     

M-PSK突发通信测试中DFT内插载波盲估计算法研究

在宽带通信信号实时多域分析通用架构基础上,针对宽带M-PSK突发通信信号实时多域分析中的快速载波同步,提出了一种基于离散傅里叶变换(DFT)插值的载波频偏相偏联合估计算法.该算法根据最大似然估计理论,首先对定时同步后的被测信号进行非线性变换去除调制信息,然后利用DFT变换得到载波频偏相偏粗估计,最后通过线性内插改善估计精度,实现载波频偏和相偏的精确估计.仿真及实验结果表明:通过内插算法处理后,载波估计误差方差更加逼近克拉美-罗(Cramer-Rao bound)界.该算法可在不增加DFT变换点数情况下,提高DFr对频率和相位的分辨力.     

高精度保偏光纤拍长测试

基于光相干域偏光测试技术,提出了一种高精度的保偏光纤拍长测试方法,实现了不同结构、不同尺寸保偏光纤的拍长测试。阐述了光相干域偏光测试技术原理并推导出测量方程;以迈克尔逊干涉仪为基础建立了测试系统并采用调制解调技术实现了信号的高精度检测。实验结果表明,系统的测量精度为0.01 mm。在此系统上进行了测试精度和重复性研究并对不同结构和尺寸的八种保偏光纤进行了实际测量,拍长测量精度和重复性均优于0.01 mm。     

调制域测频原理及工程实现

本文介绍了调制域这一新概念,着重分析了调制域测频方法,给出了所实现的调制域测频系统框图,展示了调制域测试的关键技术：内插技术和无间隔计数技术,介绍了游标内插法,独立提出了斜波内插法和孪生链。     

基于调制域分析仪的跳频信号自动测试

本文介绍了调制域分析仪的测频原理和关键技术,详细说明了用调制域分析仪测试跳频信号的方法。     

基于dsPIC移频电路系统设计

介绍了基于dsPIC的测试系统的结构,以及对移频信号进行测试的原理和算法。采用同时从时域和频域两个分析域着手的方法,避开了利用频谱幅值求取频偏进而获得上下边频的方法,并且运用频谱细化技术,提高了运算处理的速度以及频率测试精度。文中给出了简洁实用的算法。试验结果表明,该方法能够对移频信号进行准确快速的测量。     

高阶QAM实时多域分析联合载波同步算法研究

在宽带通信信号实时多域分析通用架构基础上,针对宽带高阶QAM通信信号实时多域分析,提出了一种面向测试的高精度快速联合载波同步算法.该算法采用基于离散傅里叶变换(DFT)的载波频偏盲估计算法和改进的双模载波同步环路,并引入频谱滑动平均、输出跟踪保持和环路参数自动调节等处理机制, 可在极大频偏条件下快速实现载波相位精确跟踪.研究表明:在实时分析带宽为20 MHz的条件下,采用该算法对码率为6.4 MSps的宽带256QAM信号进行实时多域分析.载波同步的最大频偏捕获范围能够达到±10 MHz;载波频偏盲估计精度较以前算法提高了5倍;载波恢复环路能够在大约1 800个符号周期内锁定,并实现载波相位精确同步.     

基于固态自旋系综NV色心微波调制的磁传感技术研究（英文）

针对传统磁场检测设备分辨率低、测量精度低的现状,提出了一种基于金刚石NV色心微波频率调制进行磁检测的方法。通过频率调制方法,可以降低测量系统中低频噪音干扰,提高测量灵敏度。首先通过扫描微波频率得到ESR谱线,然后利用混合高频正弦调制信号进行频率调制,并使用锁相放大器对频率进行锁定,得到频率与光谱一阶导数成比例的信号。实验结果表明,磁场检测灵敏度可达17.628nT/Hz~(1/2)。该方法实现了高分辨率、高灵敏度的磁场检测。     

频率调制随机共振的数值分析

对随机共振技术运用于强噪声背景下的弱信号检测进行了研究,提出了用频率调制的方法,实现了在大参数情况下从强噪声中检测微弱周期信号.数值计算结果表明,该方法可形成低频信号,该低频信号通过双稳系统易产生随机共振,能使微弱的故障信号特征突出、明显,易于捕捉.     

偏振调制测距系统频率漂移误差及其补偿

偏振调制测距方法中,频率测量的稳定性是影响测距精度的关键因素。为提高偏振调制测距系统中频率测量精度,提出一种双向扫频频率测量方法。分析了偏振调制测距原理及测频精度与测距精度的关系,探讨了频率漂移量的影响因素和频率漂移规律,证明调制深度和热致附加相位差是影响频率漂移的重要因素。利用正向扫频和反向扫频时频率漂移方向相反的特点,提出频率漂移误差补偿方法,可在低调制深度条件下补偿热致附加相位差引起的频率漂移。对距离为15.23m的目标进行测量,频率测量标准差从3.822 9×104 Hz减小到5.807 5×103 Hz,测距误差从7.513 7mm减小到0.866 7mm,验证了该方法的有效性。     

An Accurate Ultrasonic Distance Measurement System with Self Temperature Compensation

Abstract

This study proposes an accurate distance measurement system which has self-temperature-compensation (STC) with the environmental average temperature in space, rather than a single point temperature. This system combines both the amplitude modulation (AM) and the phase modulation (PM) of the pulse-echo technique. The proposed system can reduce error caused by inertial delay and the amplitude attenuation effect when using the AM and PM envelope square waveform (APESW). The proposed system adopts two identical measurement hardware sets using the APESW ultrasonic driving waveform. The first set measures the sound velocity (the environmental average temperature information is also involved) as the result of the temperature compensation data for the second distance measuring set. Without using a temperature sensor, experimental results indicate that the proposed STC distance measurement system can accurately measure the distance. The experimental standard deviation of the linearity with respect to the distance is found to be 0.21 mm at a range of 50 to 500 mm. Moreover, the proposed system's temperature uncertainty effect produced a standard deviation of 0.093 mm, while the temperature sensor system's uncertainty effect produced a standard deviation of 0.68 mm. The STC manner is simple and can be easily adapted for robotic applications for which the temperature sensors can not easily be set up and placed. The main advantages of this STC distance measurement system are: high resolution, low cost, and ease of implementation.     

Development of a wavelength-stabilized distributed bragg reflector laser diode to the Cs-D2 line for field use in accurate geophysical measurements

We have developed a wavelength-stabilized laser diode (LD) for geophysical measurement devices, which benefit from the uniformity of laser light. Regarding this purpose, a system that has such characteristics as low power consumption, sturdiness against mechanical disturbances, and a long life with long-term frequency stability is especially required. Therefore, we adopt as the light source a distributed Bragg reflector (DBR) LD because it has various advantages concerning such properties. This paper describes the durable and compact wavelength-stabilized laser system. Since our DBR-LD oscillates at 852 nm, we selected the Cs-D2 line (6 2S1/2-6 2P3/2 transition) as a frequency reference to obtain a long-term stability in wavelength. Stabilization is performed by a feedback system using a modulation transfer (MT) method, which is a kind of Doppler-free saturated absorption spectroscopy, to acquire a saturated absorption signal with a high signal-to-noise ratio. Using this system, we could continuously lock the laser frequency to the hyperfine component of the Cs-D2 line for more than one week. By an Allan standard deviation measurement, the uncertainty of the stabilized laser frequency was found to be better than 1 x 10(-10) (<40 kHz) in a Gatetime region longer than 100 s.     

基于时间序列线性大数据分析的电力系统潮流计算方法

针对原有电力系统潮流计算方法精准程度低下的问题,设计基于时间序列线性大数据分析的电力系统潮流计算方法。依据系统调频的相关特性,给出电力系统潮流计算流程,分析基于时间序列线性大数据的电力系统调频特征。根据分析结果,在时间序列线性大数据基础上,建立电力系统潮流模型,完成电力系统潮流计算方法设计。利用 ＰＳＡＳＰ电力系统分析综合程序,设计仿真实验,对比所设计方法与原有方法数据。实验结果表明,所设计方法计算所得节点电压幅值标准差明显小于原有方法,该方法计算精准程度较原有方法更高,说明将时间序列线性大数据分析,应用于电力系统潮流计算的方法是有效的。     

微纳尺度材料内耗测量系统的设计与实现

提出了一种非接触式的内耗测量方法。通过对碳纤维材料试样进行交变静电激发,在显微系统下记录强迫振动过程的高帧率图像,完成了微纳尺度材料内耗测量系统的设计。实验结果表明该系统能实现低频和高频内耗的非接触式测量,测量频率范围大,系统扩展性强。     

Development of a three-axis acceleration signal measurement system for fMRI motor studies

The purpose of this study was to develop a three-axis acceleration signal measurement system that could measure acceleration signals without deteriorating the functional magnetic resonance imaging (fMRI) data and not affect the main magnetic field, the gradient magnetic field, which varies rapidly with time, or the radio frequency (RF) pulse during fMRI acquisition. A three-axis accelerometer was used to measure acceleration signals, and Velcro was used to attach the accelerometer module to a finger or wrist. To minimize the mutual interference effect between the fMRI system and the acceleration signal measurement system, an amplifier circuit was constructed of analog devices, and the amplifier was located in the shielded case, which was made of copper and aluminum. The acceleration signal was modulated to an optic signal using pulse width modulation (PWM), and the modulated optic signal was transmitted outside the fMRI room using a light emitting diode (LED) and optic cable. We were able to verify that fMRI data and the tri-directional acceleration signal were measured simultaneously and stably. Various movement variables such as position, velocity, and jerk could be obtained numerically. Therefore, this system could be used for studying of the relationship between various movement variables and brain motor function, especially for the study of the rehabilitation field.     

A new envelope algorithm of Hilbert–Huang Transform

The algorithm to compute the envelope-line in Hilbert–Huang Transform (HHT) has major drawbacks. This paper first introduces the problem of an envelope-line algorithm in HHT, analyses the shortcomings of two classic algorithms, cubic spline interpolation algorithm and the Akima interpolation algorithm, and then proposes an important theory called the Segment Slide Theory in light of the principle of parabola parameter spline interpolation method and proves it. Based on the theory we proposed and with intuitive geometric meaning, a new envelope algorithm, the segment power function method, is put forward. The new algorithm is superior to existing algorithms because in most situations it is more flexible than the cubic spline interpolation algorithm and smoother than the Akima interpolation algorithm as shown in the experimental examples, and it is less likely to introduce a false frequency when applied to HHT.     

Multifrequency channel microwave reflectometer with frequency hopping operation for density fluctuation measurements in Large Helical Device

In order to measure the internal structure of density fluctuations using a microwave reflectometer, the broadband frequency tunable system, which has the ability of fast and stable hopping operation, has been improved in the Large Helical Device. Simultaneous multipoint measurement is the key issue of this development. For accurate phase measurement, the system utilizes a single sideband modulation technique. Currently, a dual channel heterodyne frequency hopping reflectometer system has been constructed and applied to the Alfve?n eigenmode measurements.     

基于非正交频分复用的智能电管家数据传输系统设计

提出一种基于非正交频分复用的智能电管家数据传输系统设计。通过 PCIE 内部结构的程序控制数据流的方向,来划分系统的读操作预计写操作研究。根据预处理操作降低数据传输偏差;利用非正交频分复用技术的子载波调制信号,来提升频率利用率和降低系统数据传输偏差。通过设备采集,得到数据类型选择其对应的大体数据传输方式;利用椭圆曲线密码学与高级加密标准抵御智能电管家数据篡改攻击,运用加密反向操作和认证签名解密密文维护数据安全,从而实现智能电管家数据安全传输。仿真结果表明,所建系统数据传输时效性强、吞吐量高且丢包率低,具备极强的实用性,深入优化了智能电管家系统的推广及应用。