动态电路冲激响应中的电荷、磁链、能量守恒问题

冲激响应是电路理论分析的重要内容。由于冲激函数的奇异性,在R-C、R-L动态电路中产生冲激响应时,电荷、磁链和能量是否守恒,常引起电路学习者的疑虑,也难见对此问题进行完整、严密地分析。本文试图从由电路初始状态所引起的冲激响应、由冲激信号作用所引起的冲激响应两个方面分析R-C、R-L动态电路的电荷守恒、磁链守恒和能量守恒问题。     

用时域分析法求解冲激响应的方法

冲激响应的求解在“电路分析”和“信号分析处理”课程中是一个十分重要的内容,也是“电路原理”课程中暂态分析的重点和难点之一。在时域中,冲激响应可用三种方法求解。本文论述了时域分析法求解冲激响应的方法。本文并就一些典型电路的求解进行了较详细讨论,解题的思路和方法可作为相关内容教学的参考,以提高其课堂教学效果。     

采用高斯脉冲函数计算电路的冲激响应

电路的单位冲激响应是研究电路暂态性质的重要工具之一。为了建立电路冲激响应的物理图景,本文以高斯冲击函数作为激励源,对储能元件采用伴随模型,对一阶RC电路的响应进行仿真计算。由于考虑了冲激函数的作用过程,电压和电流是时间的连续函数,从而为理解冲激响应的物理过程提供一个正确的物理描述。同时,本文给出的数值算法亦可应用于高阶电路的暂态仿真中。     

动态电路中冲激响应初始值的求解方法

从冲激函数定义出发,剖析了冲激响应的实质,介绍两种求解冲激响应初始值的方法,通过比较,根据不同结构的电路,可以采取不同的分析方法,但是,根据能量有限的原理所得出的方法2,具有明显的优越性,只需将冲激源作用期间,电容看成短路,电感看成开路,就可得出冲激函数作用下的等效电路,从而可以很方便地分析出冲激函数在电路各个元件上的分布情况。这样就轻松地解决了冲激响应初始值求解难的问题。     

基于Nose-to-Nose校准法的取样示波器 冲激响应的一种算法

本文根据时变电路概念和信号与电路系统理论,利用Nose-to-Nose(NTN)校正法,对取样示波器的双二极管平衡型取样电路建立了时变线性电路模型,导出了kick-out脉冲和取样系统冲激响应的时域表达式,证明了该脉冲是NTN校正中的零输入响应而非冲激响应,提出了从kick-out脉冲中提取时间常数从而确定取样器冲激响应的新的数据处理方法与公式,有效地解决了NTN校正中取样管结电容变化对校正精度的影响问题.     

模拟电路浪涌信号产生机理的研究与仿真

针对某型雷达模拟电路中存在的浪涌信号,提出了一种简单、实用的冲激响应理论分析方法。对雷达产生浪涌信号的一个典型电路进行仿真,得出模拟电路产生浪涌的一个重要原因是晶体管的瞬间导通电流过大。提出了一些防止浪涌信号对模拟电路冲击的措施。     

对电路理论教程及相关文献中问题的讨论

本文指出了陈希有主编的《电路理论教程》(1版、2版)及相关文献中存在的若干概念性问题,这些问题包括冲激函数单位、冲激响应单位、阶跃响应单位、冲激响应与阶跃响应的关系。文中通过对相关公式的分析,结合逻辑推理和一些文献的观点,对问题进行了分析和讨论。     

“电路基础”教学内容的精选与讨论

为适应宽口径大类招生模式,培养基础扎实、适应性强的综合型人才的需求,我们对"电路基础"的教学内容进行了精心的选择。通过对电阻电路内容的整合,在不增加学时的情况下,增加了高级电路分析章节,扩充冲激响应、传递函数和频谱等概念的内涵,从而使学生深刻认识到自然规律的普遍性。     

一种数字有限冲激响应滤波器电路的设计

提出了一种数字有限冲激响应(FIR)滤波器电路的设计思想,克服了传统的从算法直接入手的滤波器设计方法中存在的计算量大、电路描述繁琐以及验证困难的缺点.并按此思想设计了一个通用数字FIR滤波器电路,在利用Matlab工具构造出滤波器数学模型的基础上,提出了一种滤波器电路结构,用VHDL语言对电路进行描述,并进行了电路综合和仿真.给出了该电路的数学模型和滤波结果.     

一种基于Butterworth滤波器的DAC幅频特性模型

首先分析了理想DAC幅频响应特性,然后采用沿函数和矩形脉冲函数卷积和的方式对DAC单位冲激响应建模.最后采用Butterworth滤波器的方式,建立了DAC幅频响应模型,并根据实际电路提取模型参数.仿真表明模型能够准确反映电路特性,克服了分数阶保持模型的偶数倍奈奎斯特频带内的谱峰分裂现象.试验证明这种模型与实测数据吻合.     

Windowing Design Method for Polynomial-Based Interpolation Filters

An efficient implementation for finding digitally the interpolated samples is the Farrow structure. It mimics digitally a hybrid system where a continuous-time (CT) signal is reconstructed using an analog reconstruction filter having a piecewise-polynomial impulse response. The interpolated samples are obtained by sampling reconstructed signal. This paper introduces a generalized design method for polynomial-based interpolation filters and Farrow structure. The proposed method also can be used to calculate the coefficients of Selva interpolator. In this approach, the ideal CT impulse response is truncated by using CT window functions. The obtained windowed impulse response is then approximated using the piecewise Taylor polynomial approximation. Length of the impulse response and degree of the approximating polynomial can be arbitrarily selected, and in this way the transition band width can be controlled. However, if CT fixed-window functions are used, the stopband attenuation is determined by window type and remains approximately constant with increase of length and order of the impulse response. The stopband attenuation can be controlled by using CT dynamic windows such as Kaiser window. The presented windowing design method is an effective tool for calculation of the Farrow structure coefficients, with filter performance that is comparable to the frequency domain design.     

Characterization of avalanche diode TRAPATT oscillators

The characteristics of a coaxial avalanche diode oscillator circuit are calculated and compared with experimental results. The circuit admittance, as seen at the diode terminals, is calculated in the frequency domain for "optimally tuned" experimental conditions. The impulse response function of the circuit, as obtained from the transformed admittance, is used to obtain time-evolution solutions of the avalanche diode circuit system. The impulse response is more general than the previously employed differential equation characterization of a lumped element equivalent circuit. The simulation presented of the high-efficiency mode of oscillation allowed no adjustable parameters and is in excellent agreement with experiment. The simulation verifies the original TRAPATT [1] explanation for the high-efficiency mode of oscillation.     

外磁路涡流对铁氧体开关响应时间的影响

从开关电路和响应磁场2个方面对涡流的影响进行了研究.以激励线圈等效阻抗的变化,得出涡流效应对外磁路开关电路响应时间的影响;在响应磁场方面,以典型模的方式,应用安培定律、楞次定律、电磁感应方程,以数学推导得出典型模涡流对响应磁场的影响,以此得出涡流对外磁路开关响应时间的影响因素及其量级大小.通过具体产品的设计验证,证明了结论的正确.     

相关分析法辨识脉冲响应实验设计

基于目前新工科背景下，加强工程教育的理念，设计了相关分析法辨识脉冲响应实验。通过对被辨识系统的阶跃相响应、幅频响应、输入输出特性进行理论计算和仿真分析，进而确定被辨识系统的过渡过程时间、最大截止频率和系统脉冲响应辨识激励M序列的阶数、循环周期、移位节拍、幅值，并利用运放模块搭建被辨识系统，通过STM32单片机、TFT触摸屏构建脉冲响应特性测试系统实现脉冲响应辨识。实验实施软硬、虚实结合，有利于学生理解理论知识、掌握工科学习新方法、提高综合运用知识的能力和培养创新思维。     

The damped dynamics of printed circuit board and analysis of distorted and deformed half-sine excitation

The JEDEC test standard JESD22-B111 that introduced a half-sine pulse excitation to the supports of the printed circuit board (PCB) is known to suffer from poor reproducibility. Closed formed solutions for the damped dynamic responses of the test board are developed to gain in-depth understanding of the physics. The ratio of the resonant frequency of the test board to the frequency of the half-sine excitation has been found to be the single most important parameter that governs the response of the test board. The magnitude of response increases almost linearly with frequency ratio up to the ratio of 0.7 then increases non-linearly before decreases towards a quasi-static response. In case of no damping, the test board would vibrate perpetually, except for the frequency ratios of 3, 5, 7, etc. for which the test board will cease to vibrate immediately upon the ending of the half-sine excitation. For the specific frequency ratio of 3, the test board exhibits an ideal bell shape response within the duration of the half-sine excitation. Using the closed formed solutions, simple expressions for the maximum fibre strain on the test board and the maximum stresses in the solder joints have been developed. The maximum fibre strain on the test board is proportional to the square root of its density. An ideal PCB for minimum solder joint stresses is one that has low density, high flexural compliance, and in-plane compliances. In practice, it is near impossible to introduce a perfect half-sine excitation and this inconsistency is responsible for the poor reproducibility of the JESD22-B111 test method. The developed closed form solutions were used to investigate two forms of distortions to the half-sine excitation: general shape distortion and local spikes. The former has been shown to alter the response of the test board significantly and is responsible for the poor reproducibility of the JEDEC test.     

基于柔性铰链结构的高灵敏度低频光纤光栅加速度传感器

设计了一种基于柔性铰链结构的光纤光栅加速度传感器,进行了结构理论分析,并构建有限元模型仿真分析了传感器的加速度传感特性。基于F-P滤波器构建了具有温度自补偿功能的光纤光栅加速度检测系统,并通过增加反馈控制电路,对F-P滤波器进行反馈控制,实现了系统的零点自温度补偿。对系统的特性进行了实验测试,结果表明:系统对加速度的连续激励信号和冲击激励信号均有良好的动态响应,系统的固有频率为380.0 Hz,动态响应范围可达65.6 dB,频率响应范围为10.0 ~240.0 Hz,灵敏度为236 pm/g,所设计的加速度传感器具有较强的横向抗扰能力,干扰方向灵敏度仅为工作方向灵敏度的3.5%。     

电容电荷守恒和电感磁链守恒的条件

动态电路换路时，若存在由纯电容和理想电压源构成的回路，则电容电压就有可能跃变，在含电压可能跃变的电容支路的割集中，若除电容支路外的支路中无冲激电流存在，则电容电荷守恒，否则电容电荷有可能不守恒；若存在由纯电感和理想电流源构成的割集，则电感电流就有可能跃变，在含电流可能跃变的电感支路的回路中，若除电感支路外的支路中无冲激电压存在，则电感磁链守恒，否则电感磁链有可能不守恒。文中同时给出了电容电荷不守恒和电感磁链不守恒时电路初始条件的求解方法。     

Mildly suboptimal digital filters using a host windowing approach

A digital-filter design technique is described which employs simple trigonometric windowing of a `host? digital filter. In contrast to the usual windowing rationale which uses a truncated ideal impulse response, this approach uses an optimal (finite-length-minimax) host impulse response. It is shown that optimal Hilbert-transform filters serve as suitable hosts for lowpass filters of even-length impulse response, and optimal differentiators can be used as hosts for odd-length impulse responses. The resulting windowed filters are no longer optimal, but yield approximation errors under most operating conditions.