基于阶跃激励的FM信号源调制特性评价

本文目的是评价FM信号源的外调制特性,提出了FM信号源调制传递函数的概念及其测量方法,基于阶跃响应方式,用方波调制处于外调制状态下的FM信号源,以数字存储球波器对FM信号及其外调制信号进行同步测量,用数字化解调方法解调出FM信号中的阶跃调制波形,最终获得了FM信号源的调制传递函数和频率特性的测量结果.一组实验结果验证了本文方法的正确性和可行性,该方法可用于FM信号源外调制传递函数和频率特性的测量评价.     

基于自补偿技术的时栅电流型激励信号源设计

三相激励信号源的相位对称性将直接影响时栅位移传感器性能,针对这一特点,设计了一种基于自补偿技术的电流型时栅三相激励信号源,该信号源采用直接数字频率合成技术产生三路正交的正弦信号,经相位自检和自修后,使三相激励信号源达到高稳定和高精度三相对称.实验表明该设计大大提高了时栅位移传感器的稳定性和测量精度.     

基于LabWindows/CVI的多信号源开发设计

介绍一种基于LabWindows/CVI的多信号源开发设计过程,使用了开发软面板的一般方法.通过编写回调函数响应了控件消息事件.该信号源可以产生正弦波、方波和三角波三种信号,并可以根据需要对所选波形设置不同的参数.最后经过编译运行我们成功地实现了多信号源的功能.     

磁性液体微压差传感器校准信号源的研究

提出了一种新颖的低频(0.1～100Hz)磁性液体正弦压力信号源,可用于微压差传感器校准实验,该信号源能够产生与激励电流频率相同的正弦微差压.利用单自由度受迫振动原理分析了输入电信号和输出压力信号之间的函数关系.采用有限元方法(FEM)分析了磁性液体正弦压力信号源内的磁场分布并计算了磁性液体所受磁场力.最后搭建了测试信号源性能的实验平台,并给出了实验结果,由此计算了系统的固有频率及阻尼比等特征参量.实验结果显示与理论分析一致.     

低成本精确测量A/D动态参数的方法

本文为A/D动态参数的测试提出了采用低精度激励正弦信号源进行测试的方法.基于被测ADC的特性参数与激励信号源之间的关系,通过简单的压分电路,建立起分压前后激励信号之间的联系,从而可准确估计出激励信号源的参数,进而估计出高精度和高准确度被测ADC动态参数.理论分析和仿真结果表明此方法的有效性和可行性.     

基于嵌入式系统的扫频信号源

介绍了嵌入式扫频信号源的工作原理及硬件、软件设计方案.采用基于ARM7TDMI内核的S3C4510B作为嵌入式处理器;以SA4828作为SPWM信号发生器,经过驱动电路控制IGBT模块,产生变频正弦波信号;配以键盘、LCD显示器进行信息输入、显示;采用HY39LV160 Flash作为系统存储器,并在其上移植uClinux操作系统和相应的程序,实现扫频信号源的产生.该信号源设计简单,运行可靠,功能完善,软硬件可剪裁,具有极高的实用价值.     

用于颗粒检测的高精度移相信号源

基于锁相放大技术的颗粒检测需要频率范围宽、移相精度高的移相信号源.针对现有的移相信号源在高频范围移相精度低的缺点,设计了采用直接数字频率合成技术,以2片AD9852为核心的移相信号源,给出了系统硬件设计原理.重点介绍了高精度移相、幅度闭环控制的软硬件设计.实验结果表明:该系统在保证宽频范围的同时,输出信号在相位差、频率、幅度方面都具有较高的精度,满足颗粒检测的要求.     

信号源识别的相干函数法

实际工程中所采集的多个信号往往不满足独立性，而且独立信号源的个数也常常是未知的，针对此问题，提出一种基于相干函数分析的振动信号源识别方法。该方法可用于独立、非独立以及未知独立的信号源识别。对于检测到的振动信号，用虚相干函数中的虚输入矩阵确定信号源独立个数，并以此判断信号源是否独立。对于非独立信号源，提出一种优先级排序的滤波器法。在进行优先级排序后，用重相干函数检测是否有重要信号源被遗漏，然后分别用常相干函数和偏相干函数对独立信号源和非独立信号源进行识别。随机信号的仿真试验说明，基于相干函数分析的振动信号源识别方法对信号源的识别具有满意的效果。     

超宽带毫米波信号源测量接收机的研制

目前很多单位已将毫米波信号源作为雷达测试及舰用无线电设备检测的重要设备,这些信号源输出信号质量的好坏很大程度上决定着武器装备整体性能的发挥。完成其所有参数的检定比较困难。研制超宽带毫米波信号源测量接收机。就有可靠的能力对现有的信号源设备进行测试和计量,而不受国外技术壁垒的限制,保障舰船雷达装备量值传递可靠,节约大量经费。本文讨论了超宽带毫米波信号源测量接收机技术方案、国内外现状和应用前景。     

基于DDS技术的涡流检测激励信号源

设计了一种基于直接数字合成(DDS)技术的涡流检测智能激励信号源.它以高速单片机W77E58和FPGA芯片为核心控制单元,外围配合D/A转换、滤波器、人机交互和电源管理等模块,以产生参数可调的高精度激励信号去驱动涡流探头.该激励信号源具有性能稳定、操作灵活、界面友好等特点,可以满足裂纹涡流检测系统的需要.     

Study on GNSS satellite signal simulator

Satellite signal simulator for global navigation satellite system（GNSS） can evaluate the accuracy of capturing,tracing and positioning of GNSS receiver.It has significant use-value in the military and civil fields.The system adopts the overall design scheme of digital signal processor （DSP） and field-programmable gate array （FPGA）.It consists of four modules：industrial control computer simulation software,mid-frequency signal generator,digital-to-analog （D/A） module and radio frequency （RF） module.In this paper,we test the dynamic performance of simulator using the dynamic scenes testing method,and the signal generated by the designed simulator is primarily validated.     

检测混沌背景中微弱正弦信号的神经网络方法

提出了一种提取混沌背景中微弱正弦信号的神经网络方法。该方法利用RBF神经网络对被噪声污染的混沌背景建立最优一步预测模型，结合频域处理的方法从预测误差中提取微弱正弦信号。改善了信噪比，在混沌背景中存在白噪声和任意色噪声情况下，均能检测出微弱正弦信号，微弱正弦信号与混沌背景的检测信噪比门限最低可以达到-37dB。     

Vibration component separation by iteratively using stochastic resonance with different frequency-scale ratios

It is well-known that stochastic resonance (SR) is mainly used for signal denoising and weak signal detection. In this paper, we firstly find the frequency range selection characteristic (filtering characteristic) of re-scaling frequency SR (RFSR) caused by the driving frequency limitation of bistable SR. It then follows that a novel approach to separate vibration components with different frequencies by iteratively using SR is explored. The frequencies of most vibration signals exceed the driving frequency limitation, thus by use of different frequency-scale ratios, the vibration signals with different frequency range can be extracted by RFSR. Firstly, a small frequency-scale ratio is used to obtain the vibration signal with a narrow frequency range, i.e. low frequency vibration. As the output of SR may have a phase lag, a simple phase-shift correction method is proposed to improve the accuracy of signal component separation. The phase-shift corrected signal of RFSR output is separated from the original vibration signal and the residue is treated as the new vibration signal. Then, increasing the frequency-scale ratio according to a searching algorithm, the vibration signal with higher frequency can be obtained by RFSR. Through this iterative process, several harmonic vibration components can be separated from the original noisy vibration signal. The proposed method, empirical mode decomposition (EMD) and Hilbert vibration decomposition (HVD) are respectively applied to analyzing a simulated vibration signal and extracting the fault feature of a rotor system. The contrastive results show that this proposed method has good frequency resolution and can successfully separate monocomponent harmonic signals from a strongly noisy multicomponent harmonic vibration signal while EMD and HVD cannot.     

NON-STATIONARY SIGNALS: PHASE-ENERGY APPROACH—THEORY AND SIMULATIONS

Modern time–frequency methods are intended to deal with a variety of non-stationary signals. One specific class, prevalent in the area of rotating machines, is that of harmonic signals of varying frequencies and amplitude.This paper presents a new adaptive phase-energy (APE) approach for time–frequency representation of varying harmonic signals. It is based on the concept of phase (frequency) paths and the instantaneous power spectral density (PSD). It is this path which represents the dynamic behaviour of the system generating the observed signal.The proposed method utilises dynamic filters based on an extended Nyquist theorem, enabling to extract signal components with optimal signal-to-noise ratio. The APE detects the most energetic harmonic components (frequency paths) in the analysed signal.Tests on simulated signals show the superiority of the APE in resolution and resolving power as compared to STFT and wavelets wave-packet decomposition. The dynamic filters also enable the reconstruction of the signal components (paths) from the noisy signal. A quantitative comparison was performed both for the detected path in the time–frequency plane as well as for the reconstructed signal, demonstrating the performance of the APE.     

Effect of the Size of a Flat-Bottom Hole in a Cylindrical Specimen on the Bottom-Signal Level

The effect of a change in the size of a flat-bottom hole on the level of a bottom signal measured with a normal probe at an end surface of a cylindrical specimen is considered. It is shown that this effect depends on the specimen's radius-to-length ratio. It is established that the difference in the levels of a bottom signal and a signal from a hole in the specimen is in good agreement (within 0.5 dB) with the corresponding difference obtained from the calculated DGS diagram.     

小波变换在机械系统非线性信号消噪中的应用

噪声的去除一直是信号处理中较为关键的技术之一。小波变换在时、频两域都具有表征信号局部特征的能力，突破了传统Fourier分析的局限性，很适合检测信号的奇异现像。用Daubechies小波和Fourier变换分别对洛仑兹混沌信号以及撞击流反应器压力波动非线性信号进行去噪分析，结果表明，二者的去噪效果有较大的不同，突出了小波变换用于非线性信号去噪的性能。因而，将小波用于信号消噪具有重要的意义。     

经验模分解在信号趋势项提取中的应用

研究了经验模分解方法(EmpiricalModeDecomposition,简称EMD)在信号趋势项提取中的应用,提出了基于EMD方法在不同频率限制要求下信号趋势项的定义和提取方法。通过应用于数值模拟信号及实测记录,验证了此定义的可靠性。分析结果表明,EMD方法依据信号自身的特性来定义趋势项,无需预先假定其类型,是一种提取信号趋势项的良好方法。     

相位式光电测距仪的信号源系统设计

文中介绍了一种新颖的中短程相位式光电测距系统的信号源系统。介绍了信号源电路的设计方案,并给出了相关的具体电路。     

Signal strength and noise in confocal microscopy: Factors influencing selection of an optimum detector aperture

In confocal microscopy, several factors influence the selection of an optimum size and geometry of detector aperture. These include (1) strength of signal from the specimen, (2) noise level in the system, (3) optical configuration of the microscope (e.g., reflection or fluorescence), (4) time available for signal accumulation, (5) specimen thickness, and (6) amount of reduction in axial and transverse resolution (from the theoretical maximum) that can be tolerated. It is shown both theoretically and experimentally that the size of the detector aperture critically influences the type and amount of system noise that is detected along with the specimen signal. It is also demonstrated that increasing the size of the detector pinhole does not appreciably increase the signal strength from any single thin plane, but only increases the sampling depth, enhancing brightness at the cost of a reduction in axial resolution. As a result, it is shown that there is no advantage, from the standpoint of signal strength, to using a slit aperture rather than a circular detector pinhole. Finally, it is concluded that all confocal microscopes should be designed to allow the user the capability of selecting ah optimum compromise detector aperture setting based on the particular specimen properties, type of microscopy (e.g., fluorescence or reflection) and resolution required.     

分形分析在齿轮箱缺陷检测中的应用

具有多尺度(分辨)分析和时-频局部化特性的分形分析技术,特别适用于边缘信号和峰值突变信号的处理和特征提取,因此在齿轮箱缺陷检测中和诊断将会有很大的发展前途.用分形变换的方法对齿轮传动过程中进行初步缺陷检测和诊断,结果表明分形分析在齿轮箱缺陷检测中和诊断有很好的应用前景.