基于灵敏度序列的非线性模拟电路故障诊断

对在非线性模拟电路中采用基于灵敏度序列的故障诊断方法进行了研究.针对非线性参数特性,首先采用分段线性叠代方法构建元件的线性模型,在被测电路中采用戴维南和诺顿定理等效替换;而后分段进行测前仿真,构造故障字典.采用分段线性叠代的方法,巧妙地构建了非线性元件的分析模型,避免了求解繁复的非线性代数方程或非线性微分方程.通过对两种等效替代模型进行分析和比较,指出各自的适用范围.在分段线性化后,引入工作域分析策略,简化了含多个非线性元件电路的测前分析.理论分析和相关实验为研究非线性电路的测试与故障诊断提供了新的方法.     

多载波卫星非线性信道分析

对卫星的非线性信道进行了详细分析,给出了信道仿真模型,并在此模型基础上分析了多载波信号在非线性信道中的功率回退,及其与调制方式和多载波数的关系,给出在不同系统参数下得到最优功率回退的具体方法.分析结果表明非线性信道所需的功率回退随着调制阶次和载波数的增加而增大.     

Pt100温度传感器非线性的补偿方法与电路实现

针对铂电阻(Pt100)温度传感器输出的非线性问题,结合其非线性的具体特点和船舶装备的实际使用要求,提出了一种补偿其非线性的方法,即通过动态调整流过铂电阻的激励电流,来补偿由于铂电阻随温度升高阻值增加率减小而引起的非线性,并设计了专用的非线性补偿电路.在对电路补偿原理及效果进行理论分析和计算机模拟仿真的基础上,实际制作了该非线性补偿电路,并进行了现场测试,结果表明在0~650℃的温度范围内,电路输出的非线性误差不超过0.12%.目前以本电路为核心的温度测量与控制系统已实际应用于某海军船舶装备.     

基于灵敏度分析及Volterra级数的非线性模拟电路故障诊断

为了有效解决非线性模拟电路故障诊断问题,提出了一种基于灵敏度分析及Volterra级数理论的故障诊断方法。首先采用灵敏度分析估计激励信号的有效频带范围,根据Volterra级数确定激励信号的频率成分,以使故障可测度最大化;其次基于多音激励下Volterra核的频域输出特性进行故障特征提取,并采用主元分析(principal componentanalysis,PCA)对故障特征进行维数压缩;最后构造多值分类支持向量机(support vector machine,SVM)网络进行故障模式判别。理论分析及仿真结果表明,与以往方法比较,该方法可以显著提高非线性模拟电路故障识别率,验证了该方法的有效性。     

基于多路音控电路的任意控制的研究设计

较全面地分析了常见的音控电路及音控IC模块,这些电路都具有不需专用的发射装置,电路较简单可靠,但抗干扰能力较差.而多路音控电路及IC模块一般只能进行顺序控制;且控制路数较少的缺陷.采用最常见而廉价的电子元件,采用理论分析计算与设计安装调试相结合的办法,设计制作出一种新型的,具有一定抗干扰能力的,能任意控制多路输出的音控电路,而且得到满意效果.     

基于Saleh函数的功放行为模型研究

如何精确地模型功率放大器以及模型的适用情况是系统仿真时重要的研究方面.文中在原始Saleh模型的基础上,提出了基于Saleh函数的无记忆和有记忆的非线性功放模型.利用Freescale半导体晶体管MRF21030器件模型及设计的电路从ADS中导出输入输出数据,对两种模型进行了仿真实现,得出了归一化均方根误差,并和多项式模型误差进行比较.结果表明,该模型简化了原Saleh模型的结构和减少了系数,能够精确描述功率放大器的非线性和记忆效应,适用于弱非线性系统电路中.     

红外焦平面阵列读出电路非线性的研究

在红外焦平面阵列读出电路中,非均匀性是限制其发展的主要瓶颈之一.优化读出电路的非线性可以改善焦平面阵列的非均匀性,提高红外系统的成像质量.文章主要对电容跨阻抗放大器(CTIA)型读出电路的非线性进行研究,包括该结构的积分放大器、复位管以及采样保持电路的非线性,并在理论分析的基础上提出了优化单元电路非线性的方法,设计了一个高线性的CTIA型单元电路.具体电路采用0.5μm DPTM CMOS工艺设计,仿真结果表明该单元电路功耗低,动态范围大,线性度高达99.87%.     

非线性系统的模拟电路与数字电路仿真实验平台的设计

对自动控制原理实验课程进行教学改革,设计了综合设计性实验———非线性系统分析与实验。采用Matlab对非线性系统进行了仿真,通过运算放大器设计了非线性模拟电路,并采用Multisim软件进行仿真,观测到了丰富的混沌行为。同时通过单片机处理器设计了数字电路,利用Proteus软件进行了仿真,结果与模拟电路基本一致,该实验从理论分析到模拟电路与数字电路软件仿真,从基本电路设计到具体实现,培养了学生的多学科的融合,工程能力程意识,激发了学生学习兴趣和创新精神。     

基于CCCII非线性电阻实现的蔡氏电路及其研究

利用具有低电压、低功耗、低噪声以及电可调等优点的第二代电流控制电流传输器(CCCII),实现了一种具有"蔡氏二极管"特性的非线性电阻,并结合Pspice软件对由它构成的蔡氏电路进行了计算机仿真研究.仿真结果表明:调节非线性电阻电路的相关参数,不仅可以实现具有不同斜率的非线性电阻,而且由其构成的蔡氏电路也出现了诸如平衡态、周期、倍周期、单涡卷混沌吸引子、双涡卷混沌吸引子等丰富的混沌现象.同时还给出了蔡氏电路处于混沌状态时,各相关元件的参数变化范围.     

D类功放中全数字PWM结构的非线性误差校正方法

本文针对全数字PWM结构中存在的非线性误差,提出了一种数字校正方法.这种校正方法在delta-sigma调制器的各个积分器中加入校正系数.此方法计算量小,非常易于硬件实现实时的误差校正.在此基础上设计了一个全数字的PWM电路结构,并进行了仿真.仿真结果表明,经过校正的数字PWM具有良好的线性,完全消除了非线性误差.     

A comprehensive explanation of distortion sideband asymmetries

This paper presents a comprehensive study of intermodulation-distortion response asymmetries often observed in microwave nonlinear systems subject to a two-tone or multitone test. The reasons for the different amplitudes of the two adjacent tones are first investigated under small- and large-signal regimes, using a general circuit with frequency-dependent embedding impedances and resistive and reactive nonlinearities. It is shown that this intriguing phenomenon can be mainly attributed to the terminating impedances at the baseband or difference frequencies. Multitone behavior is also addressed and its main differences from the two-tone case explained. Those theoretical conclusions are then extrapolated for real circuits and validated by measured results obtained from microwave power amplifiers of two different technologies, i.e., a GaAs MESFET and an Si bipolar junction transistor     

用算术运算法分析多频率激励微波非线性电路

用全频域谐波平衡法的算术运算法分析多频率激励下电路的稳态响应，给出了一种新的Ｊａｃｏｂｉａｎ矩阵的构造方法，能分析任意多的频率激励情况。     

Analytical study of FFH systems with square-law diversity combiningin the presence of multitone interference

An analytical study of the performance of fast frequency-hopped (FFH), M-ary orthogonal frequency-shift keyed noncoherent modulation with linear combining of square-law envelopes in the presence of multitone interference is presented. The multiple equal-power interference tones are assumed to correspond to some of the possible FFH/M-ary orthogonal signaling tones. It is also assumed that the channel fading characteristics of the signal and interference tones are independent. We evaluate the effect of the channel fading on the system's performance as a function of various parameters, such as the number of hops per symbol, the signal power to multitone interference power ratio, and the number of interference tones. Our numerical results indicate that by use of square-law time diversity combining, a large number of hops per symbol make the bit-error probability of the system more sensitive to the fading of multitone interference. Finally, the analysis has been proven valid by simulation     

An active-set approach for OFDM PAR reduction via tone reservation

Common to all orthogonal frequency division multiplexing (OFDM) systems is a large peak-to-average-power ratio (PAR), which can lead to low power efficiency and nonlinear distortion at the transmit power amplifier. Tone reservation uses other unused or reserved tones to design a peak-cancelling signal that lowers the PAR of a transmit OFDM block. In contrast to previous methods, the new active-set method proposed here converges very quickly toward a minimum-PAR solution at a lower computational cost. An efficient real-baseband algorithm is well suited for discrete multitone (DMT) modulation over twisted-pair copper wiring, where some subchannels may have an insufficient SNR to reliably send data. The real PAR problem occurs in the analog signal before the power amplifier, and results focus on this figure of merit. The performance of oversampling before applying PAR reduction is analyzed, and results show that this is necessary to sufficiently handle the analog PAR problem. An extension of the real-baseband technique can be applied to complex-baseband signals to help reduce PAR in wireless and broadcast systems. By sacrificing 11 out of 256 OFDM tones (4.3%) for tone reservation, over 3 dB of analog PAR reduction can be obtained for a wireless system.     

Efficient Multitone Detection [DSP Tips & Tricks]

This article presents the digital signal processing (DSP) tricks employed to build a computationally efficient multitone detection system, implemented without multiplications and with minimal data memory requirements. More specifically, the article describes the detection of incoming dial tones, validity checking to differentiate valid tones from noise signals, and the efficient implementation of the detection system. While the discussion focuses on dual-tone multifrequency (DTMF) telephone dial tone detection, the processing tricks presented may be employed in other multitone detection systems     

The multitone channel

The maximum bit rate of multitone QAM (quadrature amplitude modulation) over a general linear channel is found. First, the overall bit rate for an AWGN channel with a two-level transfer function is maximized, using a multitone QAM system. The power distribution between the tones and the number of bits/symbol per tone is optimized for a given symbol error rate. Extending these results to the general channel, it is shown that the optimum power division for multitone signals is similar to the water-pouring solution of information theory. Furthermore, multitone QAM performance is about 9 dB worse than the channel capacity, independent of the channel characteristics. The multitone results throughout are compared to those of an equivalent single-tone linearly equalized system. The comparison shows that the multitone system is useful for some channels, e.g. those with deep nulls in the transfer function. The maximum bit error rate over a twisted-pair channel which is performance dominated by near-end crosstalk (NEXT) is also found     

Impact of nonlinear distortion on FDM signals in radio over fiber systems with multiple RF tones

A numerical analysis model is proposed and simulated to evaluate the impact of nonlinear distortion on frequency division multiplexing (FDM) signals in radio over fiber (RoF) systems with multiple tones. Due to the multi-channels for FDM signals, the analysis on nonlinear distortion is quite different from the existing model for two-tone measurements, and the inter-modulation distortion (IMD) products is determined by channel numbers, input signal power and conventional two-tone spurious free dynamic range (SFDR). Based on a series of deducing and calculating, we obtain the important parameter dynamic range, which is beneficial for optimization of the link performance in multi-channels FDM-RoF systems.     

Multitone signals with low crest factor

After an introductory discussion of real-valued and complex signals, it is shown that minimizing the crest factor (CF) of multitone signals is closely related to the construction of complex sequences with low sidelobes in their aperiodic autocorrelation function. Inspired by this observation, a lower bound on the achievable CF is derived. Four differing algorithms for the reduction of the CF of complex multitone signals are compared with each other by computer simulation. The preferred algorithm is presented in detail, and its convergence is proven. Examples of multitone signals with up to 15 tones and lower CF than previously reported in the literature are given     

多音激励非线性互调失真特性研究

通过研究多音激励下射频通讯电路三阶无记忆非线性系统的互调失真,得到了多音互调比(IMR)、邻道功率比(ACPR)、噪声功率比(NPR)和同道功率比(CCPR)的理论计算公式,测试结果表明估算公式和实际测试结果的误差在2.56 dB之内。     

Time-varying Volterra-series analysis of spectral regrowth andnoise power ratio in FET mixers

This paper presents a direct and robust analysis technique for evaluating nonlinear distortion phenomena in FET mixers excited by multitone signals. Time-varying Volterra-series analysis has previously been proven to be appropriate for small-signal intermodulation-distortion calculations in mixers excited by simple RF signals. Spectral convolutions of the suitably mapped control voltages are introduced in this paper in order to solve the nonlinear current source calculations for narrow-band modulated or broad-band multicarrier RF signals. Simulations and measurements of a properly characterized resistive mixer validate the accuracy of this direct and noniterative analysis tool for spectral regrowth and noise-power-ratio prediction in such applications