新型RSA系列的实时频谱分析仪

RSA系列实时频谱分析仪采用了实时频谱分析技术,为开发射频技术的工程师提供了一个完整的测量套件,包括RF标识(ID)标记应用到完善的雷达应用。实时频谱分析为触发、捕获和分析随着时间变化的RF信号提供了独特的解决方案。这些仪器通过触发扫频分析仪     

基于局域网的频谱仪信号参数录取方法研究

立足实际装备,对电波监测类装备的监测原理进行了深入研究。提出了通过局域网连接频谱仪并设置参数、录取频谱仪实时显示数据参数的方法。通过设计软件实现频谱仪数据录取系统。达到丰富电波监测的测量手段、提高测量仪器的自动化水平的目的。对今后监测系统的功能实现、扩展、虚拟仪器设计都具有一定的指导作用。同时,对电波监测类装备的研制及改进也有一定的借鉴意义,可提高测量仪器的自动化水平。     

DS spread spectrum signal acquisition using adaptive threshold techniques

Initial synchronization (i.e. acquisition) of the spreading wave-form is a significant problem in spread spectrum system design. In this paper, adaptive threshold techniques are employed in a serial search acquisition scheme for direct sequence (DS) spread spectrum signals to improve the mean acquisition time of the system. Two approaches for adpative threshold modelling are presented, analysed and compared, namely the sample test approach and the probability-of-error approach. The results show that, using an adaptive threshold, a significant improvement may be achieved in the mean acquisition time for a certain range of interference-to-signal ratios (ISRS). The type of interference assumed is narrowband interference, from which DS spread spectrum systems suffer most, in addition to additive white Gaussian noise (AWGN). © 1998 John Wiley & Sons, Ltd.     

激光多普勒测速仪的频域自适应阈值检测

激光多普勒测速仪(LDV)能够实现载体速度的高精度测量,从而满足航空航天领域对高精度导航的需求。目标速度测量是建立在回波信号成功检测的基础上进行的,因此微弱多普勒信号检测是LDV的关键技术。根据光频段噪声频谱特性,提出了对有用信号频率进行带阻滤波、利用剩余噪声强度估计总体噪声强度的方法,设计了频域内基于噪声强度估计的自适应阈值信号检测算法。通过与传统的固定阈值算法的对比仿真和实验,表明该方法具有更好的探测性能,能够在保持较低恒定虚警概率条件下实现对高于信噪比为-9 dB信号的完全检测,具有抵抗噪声强度的起伏变化、算法简单、适用性强等特点。     

扩频通信系统中弱信号检测研究

介绍了一种用于扩频通信系统微弱信号检测的新方法。该方法利用了正弦函数的特殊性质，在信号未知的情况下，通过多次自相关运算成功的检测出埋没于强大噪声中的微弱正弦信号。具有理论推导简单、物理意义明确、计算量小等特点。还给出了具体信号的仿真结果。     

Narrowband weak signal detection by higher order spectrum

A study of narrowband weak signal detection by higher order spectrum (HOS) using real signals and real noise, rather than just Gaussian noise, is presented. Noisy real signals are processed using various HOS techniques. We propose to look at the diagonal slices of the bispectrum and the trispectrum as possible substitutes for the power spectrum. The result of applying these slices to weak, real signals is surprisingly good. The dramatic improvements are presented for visual inspection. The performance of the various techniques are then compared quantitatively for different signal-to-noise ratios. The diagonal slices prove to be fast and robust techniques for weak signal detection     

突发多进制扩频通信中自适应门限检测方法

针对突发多进制扩频通信系统在大频偏情况下的快速可靠检测需求,提出一种自适应门限检测方法。利用多个短码构造前导序列以降低频偏比,将短码相关峰做差分构造新的统计量,并基于信号能量构建恒虚警概率自适应检测门限,在判决时加入滑动窗口以进一步提升检测性能。仿真结果验证了算法可行性。     

使用频谱分析仪

有线电视技术人员一般会有频谱分析仪可供使用,用这种仪器来测量噪声是很方便的。在不扫频(零频距)时,频谱分析仪是一个固定调谐的选频电压表(见图3)。在扫频时,频谱分析仪直接显示某一频率范围内一系列零频距测量的结果。当频谱分析仪显示功率时,实际上是从实测电压换算而得的。     

实现宽带信号实时测频的声光频谱分析仪

针对日益复杂的电磁波环境,为突破工程可实用化的关键技术,对声光频谱分析仪进行高灵敏度、大带宽、实时响应等多方位技术攻关.阐述了高灵敏度、宽带、实时声光频谱分析仪的主要工作原理及设计方法.研制出瞬时带宽200 MHz,灵敏度优于-80 dBm,测频分辨率达1 MHz的声光频谱分析仪样机.若采用5通道同时工作,便可将带宽拓展到1 GHz,这将在电子战中具有很高的应用价值.其中,详细介绍了采用超声跟踪方式拓展声光偏转器布喇格带宽的设计以及在视频信号处理电路中首次采用的频点跟随读数方式.此种数据采集方式避免了传统设计中靠微机对信号进行处理、检出等繁琐环节所造成的时间拖延,真正做到信号的实时响应输出.     

Superconductive chirp-transform spectrum analyzer

Spectral analysis over an instantaneous bandwidth of 2.4 GHz has been demonstrated utilizing superconductive dispersive delay lines in a chirp-transform configuration. Two-tone resolution of 43 MHz and ±1.2-dB amplitude uniformity were achieved.     

Embolic Doppler ultrasound signal detection using discrete wavelet transform

Asymptomatic circulating emboli can be detected by Doppler ultrasound. Embolic Doppler ultrasound signals are short duration transient like signals. The wavelet transform is an ideal method for analysis and detection of such signals by optimizing time-frequency resolution. We propose a detection system based on the discrete wavelet transform (DWT) and study some parameters, which might be useful for describing embolic signals (ES). We used a fast DWT algorithm based on the Daubechies eighth-order wavelet filters with eight scales. In order to evaluate feasibility of the DWT of ES, two independent data sets, each comprising of short segments containing an ES (N=100), artifact (N=100) or Doppler speckle (DS) (N=100), were used. After applying the DWT to the data, several parameters were evaluated. The threshold values used for both data sets were optimized using the first data set. While the DWT coefficients resulting from artifacts dominantly appear at the higher scales (five, six, seven, and eight), the DWT coefficients at the lower scales (one, two, three, and four) are mainly dominated by ES and DS. The DWT is able to filter out most of the artifacts inherently during the transform process. For the first data set, 98 out of 100 ES were detected as ES. For the second data set, 95 out of 100 ES were detected as ES when the same threshold values were used. The algorithm was also tested with a third data set comprising 202 normal ES; 198 signals were detected as ES.     

频谱检测门限与n-out-of-K融合规则的联合优化

为了减少计算复杂度,提出联合优化检测门限λ和n-out-of-K融合规则的算法.以λ和n为参数建立目标函数,并将参数以二进制形式表示,从而把算法转化为组合优化问题.接着,采用基于样值修改的互熵优化方法渐次逼近最优的参数.仿真表明,该算法在获得与已有算法几乎相当的总错误率情况下,可有效降低平均搜索次数,且随着K的增加搜索次数增加更平缓.     

Micro-emboli detection: an ultrasound Doppler signal processing viewpoint

Several studies have been carried out in the last twenty years on the characterization and detection of cerebral artery emboli. From the detection point of view, the existing methods are largely based on the classical Fourier analysis of which the well known limitations provide poor accuracy. This paper first recalls existing methods based on Fourier, Wigner-Ville and wavelet approaches. It then presents new emboli detection methods based on parametric signal processing approaches. The basic idea of these parametric methods is to compare the Doppler embolic signal to its autoregressive model. The detection principle consists in constructing a decision information which contains the signature of the micro-embolus being sought. The detection is finally evaluated using receiver operating characteristic (ROC) curves. Comparison between the new methods and classical approaches is performed using a realistic embolic signal simulation. Furthermore, to validate our theoretical study, we tested our new algorithms using in vivo signals. This comparison shows the significant inaccuracy of existing methods to detect micro-emboli.     

音频信号分析仪

以单片机和FPGA为核心的音频信号分析仪,利用傅里叶变换FFT法分析音频信号频谱.该分析仪主要由信号前级调理、有效值检波、采样保持等功能模块组成.频谱测量频率范围为20 Hz～10 kHz,频率分辨率达到5 Hz,幅度范围(峰-峰值)为10 μV～20V.系统设计控制简单,设计成本低,具有很高的实用价值.     

基于噪声分布特性的脉冲信号自适应门限检测

通过分析数字脉冲信号幅度差分的概率分布模型,得到噪声的分布特性,并推导出用于脉冲信号检测的时域自适应门限。该门限可通过计算信号幅度差分绝对值的均值直接得到。该门限算法的第一个优点是门限值仅与噪声统计特性相关,与信号无关,可避免传统自适应算法中检测门限被强信号拉高,造成强信号附近的弱信号漏检问题;第二个优点是计算复杂度低,非常适合于实时性要求高而资源不足的现场可编程逻辑门阵列（FPGA）等硬件平台实现,为脉冲信号的实时捕获和后续的侦察处理提供支撑。     

小波谱及其在线性调频信号检测中的应用

在前人工作的基础上,选用了高斯线调频小波作为基函数,研究了信号的小波谱,给出了小波谱在时间域及频率域的平滑谱并与傅里叶谱进行了比较.线性调频信号的检测与参数估计是一个广泛受到关注的问题,分析了线调频信号的小波变换,并提出了基于小波谱的线性调频信号检测的算法.     

音频信号分析仪

以单片机和FPGA为核心的音频信号分析仪,利用傅里叶变换FFT法分析音频信号频谱。该分析仪主要由信号前级调理、有效值检波、采样保持等功能模块组成。频谱测量频率范围为20H加10kHz,频率分辨率达到5Hz。幅度范围（峰-峰值）为10μV-20V。系统设计控制简单,设计成本低,具有很高的实用价值。     

基于检测门限优化的DVB-T信号联合检测算法

针对检测过程中认知信号检测门限难以合理设定以及检测准确率不高的问题,根据数字电视地面广播(DVB-T)信号循环前缀特征,给出一种联合能量检测与循环前缀相关检测算法。该算法将虚警概率与检测概率的加权作为门限的函数,通过最小化函数获得优化检测门限,最终达到提高系统检测性能的目的。仿真结果也表明,在信噪比为-25~-10 dB时,对比传统能量检测算法,采用优化判决门限的能量检测算法,检测概率提高了10%~22%,联合检测算法的检测准确率提高了2%~25%。     

在频谱仪上建立频谱数据库

频谱仪的应用很广泛,对于我们无线电管理部门来说,监测、检测、干扰分析等工作都可以利用它.现介绍我站对于频谱仪的一种用法. 我们尝试在频谱仪中建立频谱数据库.现以R/S公司的FSP13型频谱仪为例,介绍一下这种用法(无需安装键盘、鼠标).     

Selecting an optical spectrum analyzer

One of the most common measurement instruments found in a modern optics laboratory is the optical spectrum analyzer (OSA). These instruments measure the optical power spectrum of light emitted from optical sources, as well as light generated from optical interactions with matter. OSAs are based on several technologies. Each technology offers strengths, but also has limitations. Choosing the correct technology for a measurement application requires understanding the concepts of sensitivity (the ability to measure low power optical signals), dynamic range (the ability to measure low power signals), resolution (the ability to measure two signals separated by a small wavelength difference), amplitude accuracy (the ability to measure the absolute optical power present), and wavelength accuracy (again, the absolute value)