基于复调制细化谱分析的轧辊偏心谐波参数估计

针对轧辊的上、下支撑辊偏心信号是密集型频谱的特点,提出了一种基于复调制细化谱分析方法的轧辊偏心谐波参数估计新方法。利用复调制细化谱分析方法准确估计出偏心谐波的频率及幅值;同时,结合快速傅里叶变换算法估计出偏心谐波的相角参数。仿真实验结果验证了该方法在偏心谐波参数估计上的有效性和可行性。     

Carrier wave frequency multiplication of AM signals

Until now carrier wave frequency multiplication has been applied in CW, PM and FM techniques. However, it has never been considered as applicable to AM signals. This is due to unsupported opinions that it would distort the envelope of AM signals. Theoretical considerations were carried out with the use of the double Fourier series expansion. The results have shown that it is enough to have an uninterrupted flow of the envelope through the amplifier to have a nondistorted envelope in both amplification and frequency multiplication. The results were verified experimentally and by observations of BC and TV stations at their harmonic frequencies. The conclusion has been made on AM signals having two or more frequency fringes, e.g.: single tone DSB, two tone SSB     

Novel adaptive IIR filter for frequency estimation and tracking [DSP Tips&Tricks]

In many applications, a sinusoidal signal may be subjected to nonlinear effects in which possible harmonic frequency components are generated. In such an environment we may want to estimate (track) the signal's fundamental frequency as well as any harmonic frequencies. Using a second-order notch filter to estimate fundamental and harmonic frequencies is insufficient since it only accommodates one frequency component [1], [2]. On the other hand, applying a higherorder IIR notch filter may not be efficient due to adopting multiple adaptive filter coefficients.     

A novel chip-interleaving DS SS system

This paper proposes a chip-interleaving direct-sequence (DS) spread-spectrum (SS) system. Its performance is analyzed under ON-OFF wide-band jamming, and closed-form bit error rate (BER) performances of two special cases of the system are obtained. The behavior of the system under tone interference is also studied. The average signal-to-noise ratio of the system is given as a function of tone interference frequency, and the system BER performance under harmonic tone jamming is then investigated. The system is compared with a conventional system using numerical examples     

谐波电流与谐波阻抗的估算——工业与建筑电气系统谐波问题之二

本文介绍了电气设备发射的谐波电流大小以及与设备的哪些参数有关和如何估算大小，指明了近代出现电压型谐波源的谐波量更大，比较分析了单相负载中有不同的谐波源时，如何估算中性线电流IN的大小，简单介绍了谐波阻抗计算的难点所在。     

Smith-Purcell radiation from a narrow tape helix

A theoretical investigation of a narrow tape helix excited by a modulated electron beam gives quantitative results which can be used to estimate the strengths of interactions obtainable in experimental configurations. Extensive results are presented for the radiation emitted by a single fast space harmonic when a slow beam is in synchronism with the azimuthally symmetric space harmonic. The effects of beam velocity, frequency, beam diameter, tape width, and pitch angle are illustrated. The analysis also demonstrates the influence of the synchronism or electromagnetic resenance condition on the interaction and, further, points out the usefulness of the complex Brillouin (k - β) diagram in predicting some of the quantitative as well as most of the qualitative properties of this influence.     

基于自适应小波包变换的直接序列扩频通信窄带干扰抑制技术

本文提出一种基于小波包变换的直接序列扩频通信窄带（单、多音）干扰抑制技术。该技术通过小波包分解将信号和干扰分离,然后再对滤波处理后的分解结果进行小波包合成,以此达到窄带干扰去除的目的。文中对这种方案的性能进行了分析并给出了仿真结果。结果表明,与传统的方法相比,它具有较好的误比特率性能,较快的干扰定位速度和简单的计算复杂度。是宽带系统中行之有效的窄带干扰抑制方法,尤其适合于窄带干扰以近似于比特率的速度快速变化的场合。     

电光调制器偏置点抖动控制对射频信号的影响

马赫-曾德尔电光调制器的偏置点控制是光载射频传输链路中一项十分关键的技术。为了分析马赫-曾德尔电光调制器偏置点抖动控制对射频信号的影响,用贝塞尔级数展开再进行频谱分析的方法对系统输出信号成分进行了理论分析,设计了马赫-曾德尔调制器任意点控制系统并进行了实验验证。用MATLAB进行仿真后可知,在输入射频功率为18dBm时,抖动信号幅度需小于45mV,2次射频信号对抖动信号引起的频率分量抑制比才能大于20dB;而在输入射频功率为10dBm时,这个幅度要小于19mV。改变抖动信号幅度进行实验,得到2次射频信号对抖动信号引起的频率分量抑制比与仿真结果误差始终保持在3dB~3.2dB左右。结果表明,马赫-曾德尔电光调制器工作在线性偏置点时,抖动信号引起的频率分量是可以忽略的;但将调制器偏置控制在最低偏置点时,对射频信号的影响不可忽略。     

多族谐波信号估计的子空间匹配投影算法

该文根据子空间匹配投影分解算法,将信号自适应地分解在谐波子空间上,得到一种多族谐波信号参数估计的方法。这种方法利用插值FFT算法和谐波参数的先验信息,能分离基频或谐波频率结构较为紧密的不同族谐波分量,谐波频率估计精度高。仿真表明,这种新方法能准确地估计基频频率、谐波频率和阶数,对随机相位抖动也不敏感;用于分析实船噪声也准确反映了船舶辐射噪声功率谱的线谱规律和特点,较好地揭示了船舶的螺旋桨现场实际运行状况,是一种很有价值的多谐波参数估计方法。     

速调管发射机射频信号频谱特性分析

发射信号频谱质量的好坏与雷达动目标探测性能高低密切相关.文中分析了脉冲调制波形前后沿抖动、电网谐波、速调管工作状态等方面因素,对发射机射频信号频谱质量产生的影响.同时,以一套速调管发射机为实验系统,进行实验分析和验证.以实验数据的形式,分别指出以上各种因素对发射系统射频功率频谱质量影响程度.对速调管发射机的工程应用,具有一定的指导意义.     

多音干扰信号对直扩通信系统伪码捕获过程的干扰效果分析

传统的对直扩通信系统干扰样式分析一般认为多音干扰能量分散,干扰效果不如单音干扰理想。从组成多音干扰的每一个单音干扰分量入手,分析其干扰效果,进而得到多音干扰的总体干扰效果。仿真结果表明:在有用信号频率无法准确侦察的情况下,多音干扰能够有效提高干扰范围,干扰效果较好;在确定多音干扰频率分布时,应该充分考虑有用信号频率的分布,做到在其频率范围内的任意有用信号都有一个或者多个单音干扰分量能够对其有效干扰;在确定多音干扰的功率分配时,应该充分考虑有用信号频率的概率分布,对于干扰有用信号频率出现概率较大区域的单音干扰分量,其功率也应该较大。     

考虑孤岛现象的储能系统奇次谐波频谱分析

为了实现对电力储能系统的协调控制能力,提出基于孤岛现象的储能系统奇次谐波频谱分析方法,构建多类型储能系统的奇次谐波检测模型,在孤岛现象作用下进行储能系统的低频成分抑制,将总储能中的低频成分指派给蓄电池,根据储能系统奇次谐波分量,进行超级电容器之间的功率分配,获取能量型储能系统奇次谐波频谱分量,采用波动平抑策略,在考虑孤岛现象作用下,基于模型预测控制算法进行储能系统奇次谐波频谱分析和特征提取,实现功率型超级电容器储能之间的功率优化分配。仿真结果表明,采用该方法进行储能系统奇次谐波频谱特征提取的准确性较好,提高了储能系统的协调控制能力,储能功率得到提升。     

雷达发射机信号谐波带宽模型分析

在对雷达间电磁兼容状况进行预测时,需要对雷达的谐波带宽进行分析.从谐波的产生机理出发,运用傅里叶变换方法,深入分析了雷达谐波带宽规律及其产生原因.结果发现,常规脉冲调制、高重频的谐波带宽和基波的带宽相比是相等的,线性调频的谐波带宽呈整数倍数变化,而相位编码的奇数次谐波和基波的带宽相比是相等的,偶数次谐波带宽很小.本研究...     

乘性和加性噪声中二维谐波频率估计

噪声中的谐波恢复问题是信号处理领域的一个典型问题,在众多领域中有着广泛的应用。本文主要研究零均值乘性和加性噪声并存下的二维谐波信号频率估计问题,提出了一种基于数据矩阵的奇异值分解和子空间的旋转不变性的零均值乘性和加性噪声中的谐波频率的估计方法。乘性噪声为零均值情形下传统的估计方法往往难以直接应用或估计失效。本文利用谐波模型信号特征,通过对观测信号进行平方运算构造了一个数据矩阵。通过对数据矩阵的特征值进行理论分析,结合子空间旋转不变性,得到了零均值乘性和加性噪声中的谐波频率和数据矩阵之间的一种内在关系。这个性质可以用于零均值乘性和加性噪声并存下的二维谐波信号频率估计,并且所得的二维频率能自动配对。仿真实验验证了本文所提算法的有效性。      

The “Harmonic” Rejecting Correlation Function

A classical problem in signal processing is accurate estimation of fundamental frequency/periodicity of periodic signals at low SNR. Typically, researchers address the estimation problem, assuming that the signal environment is a sum of sinusoids in white Gaussian noise. If the signals and noise are pulsed, the situation is much more complex since normal FFT based methods result in spectra which are sums of harmonic structures. Sorting radar signals can be especially difficult since there may be many pulsed signals present in a low SNR impulsive noise environment. In this paper, a method equivalent to integration along a hyperbola on the Wigner distribution is presented. This transform, which is closely related to both the Fourier transform and the correlation function, has the property that a periodic signal produces an expected non-zero complex-valued bulge at only the fundamental. The phase, magnitude and position of the correlation bulge are sufficient to characterize the time-domain pulse train. Finally, a simple super-resolution method is presented which may be used to refine the fundamental frequency/period estimate.     

Phase-locked millimeter-wave two-port second-harmonic Gunnoscillators

Two-port harmonic oscillators have been developed which are suitable for voltage-controlled-oscillator (VCO) operation in frequency stabilized systems. Two oscillator designs are presented. The first has a fundamental frequency cavity located above the harmonic output cavity and the fundamental is coupled by means of the Gunn device bias-line filter. The second design is an in-line structure which uses a waveguide taper as the filter element separating the fundamental and harmonic frequency components. The latter design is a translation of the first oscillator concept onto a single plane, so that the prospect of an integrated monolithic version is conceivable. The performance of the oscillators is discussed, and a demonstration of their use in a heterodyne phase-locked loop control system is presented     

Mean-Square Crosstalk in Tamed Frequency Modulation

An analytical expression for evaluating the mean-square crosstalk between adjacent channels in coherent tamed frequency modulation (TFM) systems is presented. Numerical results are obtained and compared to previous crosstalk results for minimum shift keying (MSK); the substantial superiority of TFM is confirmed. An equivalent white Gaussian noise model for crosstalk is included and used to estimate performance degradation as a function of frequency separation between channels. The crosstalk results are also used to show that TFM is about 0.9 dB more sensitive to tone jamming than MSK.     

DS/BPSK扩频系统单频干扰方法研究及仿真实现

介绍了DS/BPSK扩频系统的基本原理,分析了单频干扰下的抗干扰性能,给出了单频干扰DS/BPSK扩频系统的最佳频率位置,建立了基于Simulink的单频干扰下的DS/BPSK扩频系统仿真模型,通过Simulink仿真分析,给出了单频干扰下系统各个阶段的频谱图及不同信噪比下的误码率,仿真结果表明:该方法对DS/BPSK扩频信号中心频率区域的干扰效果极其明显.     

On the blind estimation of the parameters of continuous phase modulated signals

In this paper, a blind estimator of the technical parameters of continuous phase modulated (CPM) signals is proposed. It consists in estimating jointly the modulation index, the symbol period and the frequency offset. It is based on the following observations. First, the inverse of the index is the smallest positive real number a CPM signal should be raised to in order to generate a deterministic harmonic signal; second, the frequencies of the harmonic signal are simply related to the symbol period and the carrier frequency. The practical implementation of this joint estimator is described and the asymptotic behavior of the estimation error is studied. If N is the number of signaling intervals, the estimate of the modulation index is shown to converge to a non-Gaussian distribution at rate 1/N, while the estimate of the frequency offset and the estimate of the symbol period converge at rate 1/N/sup 3/2/. We also investigate the case where the modulation index and the symbol period are available at the receiver side. An estimator of the frequency offset is proposed by adapting the above joint estimator to the latter case. The asymptotic behavior of this estimator is studied and compared with the case where all of the parameters are unknown, so as to evaluate the possible degradation of the performance due to the ignorance of certain technical parameters. Simulations results sustain our theoretical claims.     

Detection of harmonic sets

We examine the detection problem of signals with narrowband, harmonically related components received by a passive sensor array. We investigate detector structures based on the Fourier method. The harmonic detector estimates the total signal power by combining the DFT coefficients from harmonic frequency bins. This power estimate is normalized by the estimated background noise power and then compared to a threshold. We investigate two harmonic detector structures: one that operates with coherent, correlated signals and the other with uncorrelated harmonic signals. We derive statistical laws governing both detector structures that facilitate setting a power threshold for a given probability of false alarm; and present upper- and lower-bounds for the probability of detection. The results developed and presented demonstrate the inherent advantage of the harmonic detector. At operating conditions characterized by low signal-to-noise power ratio values the harmonic detector exhibits enhanced detection performance by combining the estimated signal power from harmonic frequency bins. We generalize results from single-bin and harmonic detector structures and present them as special cases of a unifying framework