Analysis of the effect of various physical and technical factors on the efficiency of adaptive algorithms of processing of hydroacoustic signals

This paper presents results on evaluating the impact of a set of physical and technical factors on the effectiveness of classical and projection fast adaptive algorithms. The factors include the conditions of signal propagation, including multipath; the noise-signal situation; signal fluctuations due to scattering in the medium; the parameters of the receiving antenna, including the amplitude-phase value of element dispersion; and the parameters of the spectral signal analysis at the output of the antenna elements.     

Accuracy of Determining Reverberation Parameters during Recovery of a Signal with Reverberation Distortions in the Case of Discrete Delays

We discuss the accuracy of determining reverberation parameters, which is required to recover a signal with reverberation distortions. It is shown that if the signal with distortions is digitized under conditions of the sampling theorem, then it is insufficient to determine the delay time of the retarded signal with an accuracy of the sampling interval. We present an iterative algorithm for determining the reverberation parameters with sufficient accuracy.     

光束束宽对自散焦介质中诱导光束聚焦的影响

影响自散焦介质中诱导光束聚焦过程的方程参量和初始条件共有5个，即两光束波长比(方程参量)、抽运光和信号光的初始振幅、两光束初始束宽比和两光束中心初始间距。通过数值计算讨论了初始束宽比在不同初始光束间距和波长比情况下对信号光聚焦过程的影响，得到了信号光聚焦效果的最佳初始参量条件。从而实现了对影响自散焦介质中诱导光束聚焦过程5个参量的完整详细研究。     

Theoretics of remote acoustic monitoring of the level and density of fluid contacting media at the interface

We present a method for monitoring the physical parameters of a medium, based on processing of an acoustic signal reflected from the studied medium. The method makes it possible to rapidly and simultaneously measure the level and density of the reflecting medium owing to acoustic sounding with pulses of different shape. We have obtained the analytic dependences relating the controlled parameters to the phase and amplitude spectra components of the reflected acoustic signal.     

Experimental investigation of the stability diagram for Paul traps in the case of praseodymium ions

The present paper describes an investigation of non-linear resonances of praseodymium ion clouds stored in a Paul trap as a function of the storage parameters. These have been observed in traps with different ring electrode diameters. In these different traps the resonances occur for different values of the operating parameters. Discrepancies with the approximation model for one ion have been found. The intensity of the fluorescence signal and the Doppler half width have been recorded as a function of one of the storage parameters: q. We use our results to optimize the fluorescence signal of the stored ions, which is especially useful in the case of the double-resonance method.     

Effect of thermal nonlinearity in high-absorption media on the parameters of the photoacoustic signal detected by the gas microphone method: The fundamental and second harmonics

A perturbation theory is put forward that describes the effect of thermal nonlinearity due to the temperature dependence of the thermophysical parameters of high-absorption systems with a low thermal conductivity on the parameters of the photoacoustic signal detected by the gas microphone technique. It is found that the dependence of the photoacoustic signal amplitude on incident beam intensity I ₀ stems from the dependence of the illuminated surface temperature on I ₀. This dependence is a complicated function instead of being a simple quadratic function as was expected. In the limiting cases (μ_sβ ? 1 and μ_sβ ? 1), this contribution to the photoacoustic signal amplitude is described by simple expressions, which are convenient for determining the thermal coefficients of the thermophysical parameters of the medium. It is found that the thermal nonlinearity significantly affects the photoacoustic signal phase in the frequency region meeting the condition μ_sβ ～ 1. In the above limiting cases, its effect is insignificant. A theory of generation of the photoacoustic signal second harmonic is proposed. The second harmonic is related to the temperature dependence of the thermophysical parameters of the buffer gas and sample. It is shown that the amplitude of the signal is a quadratic function of the incident beam intensity and varies with its frequency as ω^?3/2 for μ_sβ ? 1 and ω^?5/2 for μ_sβ ? 1.     

脉冲激光探测的最大探测距离的研究

脉冲激光探测的最大探测距离与发射信号功率有关,根据系统发射端瞬时功率的形式,通过计算得出了脉冲激光平均发射功率和最大瞬时功率分别与驱动电流的脉冲上升沿时间、脉冲宽度、脉冲重复周期的关系.结合传输衰减、弱信号检测和信号预处理过程中的信号功率变化,得出了最大探测距离与激励电流波形参数、光电探测器参数、信号预处理电路噪声、信...     

The concise fractional Fourier transform and its application in detection and parameter estimation of the linear frequency-modulated signal

A concise fractional Fourier transform(CFRFT) is proposed to detect the linear frequency-modulated(LFM) signal with low signal to noise ratio(SNR).The frequency axis in time-frequency plane of the CFRFT is rotated to get the spectrum of the signal in different angles using chirp multiplication and Fourier transform(FT).For LFM signal which distributes as a straight line in time-frequency plane,the CFRFT can gather the energy in the corresponding angle as a peak and improve the detection SNR,thus the LFM signal of low SNR can be detected.Meanwhile,the location of the peak value relates to the parameters of the LFM signal.Numerical simulations and experimental results show that,the proposed method can be used to efficiently detect the LFM signal masked by noise and to estimate the signal's parameters accurately.Compared with the conventional fractional Fourier transform(FRFT),the CFRFT reduces the transform complexity and improves the real-time detection performance of LFM signal.     

The use of multidimensional perceptual models in the selection of sonar echo features

The development of an accurate and efficient sonar-target classification system depends upon the identification of a set of signal features which may be used to discriminate important classes of signals. Feature selection can be facilitated through the identification of perceptual features used by human listeners in discriminating relevant sonar echoes. This study was conducted to establish a more reliable means of identifying perceptual features in terms of physical signal parameters as an initial step toward the development of an automatic sonar-target classification system. The results of an experiment involving eight subjects and six sonar echoes are presented. A model of the perceptual structure of these echoes was derived from subject similarity judgments using a multidimensional scaling (MDS) technique. It was found that three perceptual features accounted for the similarity judgments made by the human listeners. Echoes modified along candidate physical dimensions were employed to aid in the identification of perceptual dimensions in terms of physical signal parameters. The three perceptual features could be associated with signal parameters involving the amplitude envelope of the echoes.     

分数阶双稳系统中的非周期振动共振

在受二进制非周期信号和周期方波信号激励的分数阶双稳系统中,研究了非周期振动共振问题,用于微弱非周期信号的检测和增强.当非周期信号脉宽较大时,系统为小参数,通过调节周期方波信号的幅值,能够实现非周期振动共振.当非周期信号脉宽较小时,分别通过变尺度法和二次采样法实现了非周期振动共振.使用变尺度法,得到的大参数等价系统能够匹配任意小的非周期信号脉宽,其中变尺度系数是该方法在使用过程中需要选择的关键参数.使用二次采样法,二次采样后得到的非周期信号具有较大的脉宽,能够匹配原先的小参数系统,其中二次采样频率比是该方法使用过程中的关键参数.这两种方法虽然实现非周期振动共振的物理过程不同,但能够达到相同的效果.系统阶数对振动共振产生影响,随着阶数的增大,发生最佳振动共振时所需要的辅助信号幅值变大,同时系统输出的最佳时间序列与输入非周期信号之间的相似性增强.     

Phase Analysis of the Activity of a Voice Source

Acoustical Physics - Mathematical models are proposed that make it possible to relate the parameters of a voice source with the parameters of the phase-frequency responses (PFR) of speech signal...     

二次采样用于随机共振从强噪声中提取弱信号的数值研究

提出了二次采样的随机共振(SR)技术，并利用该技术，实现了绝热近似理论在大参数条件下，从强噪声中提取弱信号的目标.为便于应用，研究了二次采样随机共振方法在弱信号检测中相关参数之间的关联性.数值分析表明，该法在信号分析方面有着潜在的应用价值，有望将来应用于实测信号的数据处理. 关键词： 随机共振 弱信号检测 数值分析 非线性系统     

Optimization and control of parameters of the optical scheme of a heterodyne differential microscope

Dependences of the complex response of a heterodyne differential microscope to test objects on the parameters of its optical scheme are studied. Based on the obtained regularities, methods for controlling and optimizing these parameters are proposed. A procedure for accurately bringing the signal photodetector into coincidence with the center of the Fourier plane of the microscope is described. A method that enables one to control the focusing of the probe beams on an object under study, as well as their nonidentity, is proposed. Conditions for optimizing the size of the signal photodetector are formulated. A correlation between a detuning of the main parameters of the microscope optical system and the error in determining the parameters of an object under study is established.     

Influence of the Magnetic Field Modulation on the Absorption Signal in an NMR Peak Flow Meter

The influence of the parameters of the magnetic field modulation in the analyzer of an NMR peak flow meter with flowing fluid on the magnitude and shape of the read-out signal in the mode with the modulation amplitude being much greater than the width of the resonance line is analyzed. Correlation factors are determined for the measured amplitude of the detected signal and for the duration of the magnetic mark in relation to the parameters of the magnetic field modulation in the analyzer and to the flow rate of the flowing fluid.     

简明分数阶傅里叶变换及其对线性调频信号的检测和参数估计

针对低信噪比下线性调频信号的检测问题,提出了一种简明分数阶傅里叶变换方法。该变换借助chirp相乘和傅里叶变换对时频平面上的频率轴进行旋转,以获取信号在各个角度下频率轴上的频谱分布。对时频分布呈直线状的线性调频信号,简明分数阶傅里叶变换能在特定角度上将信号能量聚集成尖锐的强能量峰,从而提高信噪比,实现对线性调频信号的可靠检测和参数估计。数值仿真和实验验证结果表明,简明分数阶傅里叶变换可对较低信噪比的线性调频信号实现有效检测,并由变换域峰值的位置对信号参数进行准确估计。相比于传统的分数阶傅里叶变换方法,简明分数阶傅里叶变换的复杂度更低,离散计算效率更高,在对噪声掩盖下的线性调频信号进行检测和参数估计时能更好地满足实时处理的要求。      

含负折射率介质的一维光子晶体构成的相干热辐射源的辐射特性及控制

电子清刷是微通道板生产流程中常用的除气方法,会引起微通道板其他性能参量的变化.为研究电子清刷对微通道板输出信噪比及增益的影响,根据信噪比及增益的定义讨论了微通道板性能参量的测试方法,研制了微通道板参量测试系统.应用微通道板参量测试系统对微通道板进行了电子清刷处理,测试清刷过程中不同阶段微通道板的信噪比及增益变化.实验表明:微通道板增益随清刷时间增加而降低,同时增益稳定性提高;电子清刷过程中微通道板的输出信号及噪音的变化率与微通道板增益的变化率基本相同,输出信噪比基本不变.增益变化是影响清刷过程中信号及噪音变化的主要因素,并且电子清刷对微通道板输出信噪比影响较小.     

Techniques for retrieval of the boundary displacement data in gas-dynamic experiments using millimeter-waveband radio interferometers

We describe a radio-interferometry method for measuring movement parameters of objects in application to gas-dynamic experiments. The origins of biasing in calculation of these parameters from measured interferograms are discussed. Bias reduction algorithms for the interferometer signal processing are described. For experimental setups with a single moving boundary, this algorithm is optimal for estimating the instantaneous phase and frequency of a narrow-band signal with bandpass prefiltering and quadrature-channel signal orthonormalization. For experiments with several moving boundaries, it provides the interferogram curve fitting by parameters of the electrodynamic model of an experimental setup. The results of test experiments verifying the reliability of the obtained information are presented. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 3, pp. 234–246, March 2008.     

Influence of ionospheric irregularities on the form of radio signal scattering spectrum in over-the-horizon radar sounding of the rough sea surface

Abstract

This paper is concerned with the backscattering of HF radio waves from the rough sea surface, which have propagated through the ionosphere with random large-scale irregularities.

For the sake of simplicity, it is assumed in calculations that the rough sea surface is a perfectly conducting surface with the known Philips power spectrum of irregularities. Ionospheric irregularities of a random medium that are isotropic and single-scale ones, with a Gaussian spectrum, are considered within the limits of the hypothesis of frozen-in irregularities.

Within the first approximation of perturbation theory, using, as the incident wave and the Green function, their geometrical-optics approximations, we obtained the expression for the backscattering spectrum of the ionospheric chirp radio signal with a Gaussian envelope. The expression involves the parameters of the receive–transmit antenna, the signal, the propagation medium, and of the scattering surface. Numerical simulation was used to investigate the influence of all the above-mentioned parameters on the backscattering spectrum. It is shown that travel of ionospheric irregularities has the largest influence on the scattering spectrum, the signal parameters mainly determine the size of the scattering area in the range, and the form of the coherent integration window determines the form of the received signal and can distort it.     

电子清刷对微通道板增益及输出信噪比的影响

电子清刷是微通道板生产流程中常用的除气方法,会引起微通道板其他性能参量的变化.为研究电子清刷对微通道板输出信噪比及增益的影响,根据信噪比及增益的定义讨论了微通道板性能参量的测试方法,研制了微通道板参量测试系统.应用微通道板参量测试系统对微通道板进行了电子清刷处理,测试清刷过程中不同阶段微通道板的信噪比及增益变化.实验表明:微通道板增益随清刷时间增加而降低,同时增益稳定性提高;电子清刷过程中微通道板的输出信号及噪音的变化率与微通道板增益的变化率基本相同,输出信噪比基本不变.增益变化是影响清刷过程中信号及噪音变化的主要因素,并且电子清刷对微通道板输出信噪比影响较小.     

大参数周期信号随机共振解析

通过调节双稳系统参数实现大参数频率范围内周期信号的随机共振, 在工程上具有重要意义. 推导了双稳系统参数的归一化变换, 利用归一化变换原理对大参数周期信号的随机共振进行了数值仿真, 阐明该原理适用于任意频率周期信号. 对大参数随机共振用电路模拟进行了实验验证, 揭示了通过调节双稳系统参数可以实现大参数频率范围内的随机共振. 分析了二次采样实现大参数周期信号随机共振的机理, 通过数值仿真与参数归一化变换方法进行了比较. 仿真结果表明, 在输入信号幅度变化的情况下, 二次采样方法易出现发散现象, 而归一化变换具有更好的稳定性与适应性.