基于虚拟无线电技术的多媒体收音接口卡设计

介绍了一种基于虚拟无线电技术的多媒体收音接口卡设计方法,可以接收调幅和调频信号,试验调试表明,接收效果良好。     

数控振荡器应用及其在FPGA中的实现

本文首先描述NCO的基本工作原理,然后介绍利用NCO产生调频信号(FM)、频移键控信号(FSK)、相移键控信号(PSK)、调幅信号(AM)和幅度键控信号(ASK)等多种调制信号的方法,最后以调幅信号(AM)为例介绍调制信号在FPGA中的实现。     

基于经验模态分解与差分包络谱的齿轮故障诊断

为了准确地进行齿轮故障诊断,结合经验模态分解与纯调频信号差分包络谱,对齿轮故障诊断提出了一种新方法;首先,对齿轮振动信号进行经验模态分解得到多个不同分量;其次,根据峭度最大分量及其相邻分量的峭度值情况,合成有效分量;然后,运用经验调幅-调频分解得到纯调频信号;接着,将纯调频信号应用经验调幅-调频分解及傅里叶变换得到纯调频信号差分包络谱;最后,观察分析纯调频信号的差分包络谱进行故障诊断;利用该方法对断齿齿轮的振动信号进行分析,验证了方法的有效性。     

基于局域均值分解包络谱和神经网络的轴承故障诊断研究

滚动轴承振动信号是非平稳信号,而且往往是由许多分量的调频调幅信号组成;轴承故障特征频率容易被高频的调频调幅信号淹没;局域均值分解技术是近年来新的时频分析方法,能够有效的处理非平稳信号;它能将多分量的调制信号自适应的分解为若干个生产函数(PF)分量,每个PF分量都是一个单分量的调幅调频信号,包含了原始信号的局部特征;利用共振解调技术对每个PF分量进行包络分析,能够有效地提取高频载波中的故障特征频率;同时,为了实现智能诊断,提取各PF分量包络信号的能量值作为特征向量,训练BP神经网络,从而达到智能诊断目的。     

基于LabVIEW的软件无线电解调系统的设计

结合当下流行的数据采集和虚拟仪器技术,采用G语言和Lab VIEW IDE对通信系统中的解调系统进行了软件无线电设计。对本地文件中已有的已调信号以及外部通用数据采集卡采集的调幅和调频信号进行解调和分析,对调频信号的解调提出了一种软件脉冲均值标记滤波算法,该算法可以很好地实现调频波的解调。本系统还可以对实时信号波形数据进行保存、打印和对历史信号的回放。该系统彰显了数据采集技术和虚拟仪器技术在无线电领域的应用优越性。     

锁相环解调信号的仿真分析

在信号解调中,使用锁相环可取得较好的解调信号。以调频波和调幅波为例,通过用MATLAB 编程与Simulink 现有组件两种方法对载波同步进行建模与仿真,并详细给出仿真设计原理以及合理选择仿真参数的方法。最后,对仿真 结果进行深入分析,并比较两种方法的可行性与优缺点。     

基于DDS技术的高精度微波信号发生器

介绍了一种基于DDS和正交上变频技术的微波信号发生器的设计,给出了完整的系统解决方案。它的工作频率范围为0.8￣2.5GHz,从而使DDS技术得以在微波频域获得应用,并且还可以产生调频、调幅、调相等各种调制信号。     

基于DDS产生线性调频信号技术研究

本文介绍了一个线性调频信号数字产生系统的设计与实现。首先对线性调频信号的两种主要数字产生方法进行了简要阐述和比较,然后根据直接数字合成（DDS）方法提出了线性调频信号产生方案,对其进行了系统实现研究,并给出了部分测试结果。     

基于通用检测平台的典型激励信号产生方法研究

为了满足在自动测试领域激励信号产生方法通用化、模块化的要求,以通用检测平台为基础来研究典型激励信号的产生过程;介绍了通用检测平台的整体结构及软件运行;归纳了自动测试领域所涉及的典型激励信号和激励资源;设计了通过定义结构体变量来获取信号特征信息的方法,并在此基础上深入分析了基于仪器功能接口的典型激励信号的产生方法;最后,以较为复杂的调幅、调频信号为例,通过封装相应激励资源的仪器功能接口,设置结构体"SignalInformation"所含"car-ampl、car-freq"等参数的值并导入到信号产生函数中,实现了信号的产生;结果证实了方法的有效性与合理性.     

高精度正弦波数字合成技术

以数字合成技术为基础。采用数字调幅、数字变频、数字移相技术，提出了一种高精度正弦波发生电路的实现方法。可实现全范围的高精度调幅调频调相。     

A local normalized method to eliminate riding waves appearing in the empirical AM/FM decomposition

The intrinsic mode function (IMF) generated by empirical mode decomposition (EMD) is usually seen as an amplitude and frequency modulation (AM–FM) signal. To obtain the FM part of an IMF, an empirical AM/FM decomposition method has been proposed by Huang and his coworkers. However, riding waves may appear in the empirical decomposition, which makes the instantaneous frequency (IF) physically meaningless. To eliminate the riding waves, riding wave turnover-empirical AM/FM decomposition method has recently been developed by Yang et al. In this paper, a local normalized method is proposed to eliminate the riding waves. Different from the previous method by Yang et al., the proposed method does not need any more empirical AM/FM decomposition and is carried out locally, which can significantly reduce computational complexity.     

数字信号处理的FPGA实现

介绍了三种常见的数字信号处理过程的FPGA实现,包括频率合成、AM调制和FM调制,并进行仿真和硬件下载验证。     

Fast-varying AM–FM components extraction based on an adaptive STFT

A new method is proposed in this article for fast-varying AM–FM components extraction. There are two prominent characteristics in this method. Firstly, a new evaluation method for the instantaneous bandwidth is established, which is based on the instantaneous slope of the time-frequency curve with respect to the AM–FM component. Secondly, a new adaptive STFT algorithm is established, which adjusts the window width by adapting to the instantaneous bandwidth at each frequency position. In order to extract multiple AM–FM components from a signal, the width of the reconstruction area is required to be determined efficiently to avoid the interference caused by adjacent components. Simulations are given in the end, which show that the proposed method has good performance for fast-varying AM–FM components extraction from noisy signals.     

A rotating machinery fault diagnosis method based on local mean decomposition

Local mean decomposition (LMD) is a novel self-adaptive time–frequency analysis method, which is particularly suitable for the processing of multi-component amplitude-modulated and frequency-modulated (AM–FM) signals. By using LMD, any complicated signal can be decomposed into a number of product functions (PFs), each of which is the product of an envelope signal and a purely frequency modulated signal from which physically meaningful instantaneous frequencies can be obtained. In fact, each PF is just a mono-component AM–FM signal. Therefore, the procedure of LMD may be regarded as the process of demodulation. While fault occurs in gear or roller bearing, the vibration signals picked up would exactly display AM–FM characteristics. So it is possible to diagnose gear and roller bearing fault by LMD. Targeting the modulation features of the gear or roller bearing fault vibration signal, a rotating machinery fault diagnosis method based on LMD is proposed. In this paper, firstly the LMD method is introduced; secondly, the LMD method is compared with another competing time–frequency analysis approach, namely, empirical mode decomposition (EMD) method and the results show the superiority of the LMD method; finally, the LMD method is applied to the gear and roller bearing fault diagnosis. The analysis results from the practical gearbox vibration signal demonstrate that the diagnosis approach based on LMD could identify gear and roller bearing work condition accurately and effectively.     

AM/FM/GIS数据模型在信息基础设施中的应用研究

AM/FM/GIS系统建设中,基于几何空间与基于逻辑空间的对象进行统一管理是核心问题。提出空间对象模型的概念,并给出严格的形式化定义。通过对AM/FM/GIS数据模型的分析,运用面向对象的AM/FM/GIS数据建模方法,实现了信息基础设施中的数据存储与管理,提高了AM/FM/GIS系统的运行效率。     

基于AD9954的多功能信号源设计

多功能信号源选用AT89C55单片微处理器对直接数字频率合成器AD9954进行控制与管理,在CPLD和A/D转换等电路配合下实现了1～ 100 MHz正弦信号输出、扫频、跳频信号输出和AM、FM、FSK、PSK、外部AM和FM调制功能.最后,使用了多种高档电子仪器对系统性能和技术参数进行了实验测试,均达到了设计要求.     

Parametric modeling of speech by complex AM and FM signals

Complex AM and FM signal models can be used for parametric modeling of speech signals. Complex AM signal model has been found to be suitable for voiced speech phonemes, whereas complex FM signal model can be used for representation of unvoiced speech phonemes. This article explains the basic principles of parameter estimation of these two models, and presents techniques for fast on-line processing of speech data and automated model fitting.     

AM/FM/GIS应用系统建设中若干问题的探讨

在进行多项AM／FM／GIS应用系统建设实践和对AM／FM／GIS的深入研究的基础上,阐述了AM／FM／GIS的特点,指出了当前AM／FM／GIS建设过程中存在的一系列问题,并从AM／FM／GIS标准,平台建设,模型集成,知识与规则的应用,多层体系结构,分布式计算等几个方面对AM／FM／GIS进行了较为详细的探讨,提出了解决相关问题的思路。     

DDS技术在智能相关流量计中的应用

在介绍超声波相关流量计工作原理基础上,论证了产生高精度正弦波的必要性。分析了DDS技术的工作原理及结构,最后还提出了一种应用DDS芯片AD9850和DSP芯片TMS320VC5402组成的正弦波信号、AM和FM信号发生器。通过实测数据表明,本文所讨论的方法和研制的系统是可行的、有效的。     

AM/FM/GIS领域模型研究

通过分析当前AM／FM／GIS在国内外日趋广泛的现状，作者指出AM／FM／GIS软件系统建设过程中存在的主要问题——软件可重用性差，指出其存在潜在的规律和本质的特征，通过找到这些规律和特征将能明显改善AM／FM／GIS系统建设的重用性。作者利用FODA的领域分析方法，对AM／FM／GIS系统进行了深入的研究，通过符合标准规范的表示方法，得到了领域特征模型、领域信息模型和领域操作模型，从不同的侧面精确描述了AM／FM／GIS的领域模型。