传输函数在滤波器综合中的应用

滤波网络传输函数的零点、极点位置对滤波性能起着决定作用。全极点滤波器的所有衰减极点都位于DC和∞处。如果将传输零点放在S面有限频率处,则会形成特殊频率响应：虚轴上（实频）的传输零点,可形成准椭圆函数的陡降幅频响应;而实轴上（虚频）的和复数（实部非零）传输零点则起到类似时延均衡网络的作用,实现线性相位传输响应。在对不同文献关于传输函数的理论表述进行分析后,总结了传输函数、特征函数以及滤波网络综合中的一些重要概念,给出了几种典型函数的极点分布图对比,提供了几种运用特殊的传输零点放置来实现特殊滤波响应的设计应用。     

基于Multisim的高通滤波器的设计与仿真分析

高通滤波为实现高频信号能正常通过,而低于设定临界值的低频信号则被阻隔、减弱.但是阻隔、减弱的幅度则会依据不同的频率以及不同的滤波程序而改变.文中阐述了对电压转移函数推导分析及电路性能的要求,并利用Multisim仿真软件对其频幅特性的分析进行.     

基于幅-频曲线的系统时域响应特性评价方法

在电磁兼容测量中,通常采用频率响应来描述一个系统的特性。而系统的频响特性一般仅提供了响应幅度的频域分布,很少给出相位信息。在连续波测量时这种幅－频信息是足够的,但在利用频域测量结果评价一个系统的脉冲响应特性时,还必须知道系统的相位信息。本文假设系统为最小相位系统,采用Ｈｉｌｂｅｒｔ变换根据系统响应的频谱幅度估计相位信息,进而将系统的频域信息转换到时域,用于评价系统的时域响应特性。根据一组磁场探头的     

旋转Y切石英谐振器的幅频非线性效应分析与研究

通过对幅频非线性效应的分析,详细地推导了旋转Y切石英谐振器的纯厚度切变模的幅频公式,并计算了幅频效应曲线.分析结果表明,通过选择切型可获得尽量小的幅频系数D,以及通过控制激励幅度来减小幅频影响的途径,从中也发现了石英谐振器的Q值(品质因素)对幅频曲线有影响.     

无源正交混频器HMC620LC4的原理与应用

HMC620LC是基泰尔微波公司推出的一款紧凑型正交混频器.该芯片由双平衡混频器、3dB耦合器(90°移相)构成,利用砷化镓MESFET工艺制作.该芯片具备宽中频输出,本振到射频端口隔离度高,镜频抑制能力优越,幅度和相位平衡出色,可用作镜频抑制混频器.介绍了HMC620LC4芯片的器件特性与结构.以及器件工作的基本原理.最后,将该器件作为下变频组件应用在0～2GHz的幅相检测系统中,对射频器件能够实现简单的幅相测量.     

有线电视网络幅频失真浅析及对策

目前 ,国内多数中小型有线电视系统仍以同轴电缆为主要手段来传输信号 ,而大多数同轴电缆网络都存在着带内幅频特性不良的问题 ,即幅频失真。幅频失真一般有两种 :一是带内各频道电平参差不齐 ,或某几个频道电平明显高于或低于其他频道电平 ;二是幅频曲线中部凸起 ,也就是所谓的中频段“鼓包”或“馒头”形曲线 ,如图 1所示。第一种失真普遍存在 ,但其失真幅度一般较小 ,对网络质量影响较小。第二种失真存在范围更广 ,失真幅度较大 ,对网络影响严重 ,其凸起的幅度随传输距离的增加而增大 ,少则有 3～ 5ｄＢ ,多则可达 2 0～ 30ｄＢ ,而且旧…     

基于过零点-极点估计的瞬时频率幅度算法

Hilbert-Huang变换(HHT)理论通过经验模态分解(EMD)提取信号的内蕴模态函数(IMF),并对IMF利用Hilbert变换得到信号的时频幅度谱和边际谱。在总结Hilbert变换理论和算法实现局限性的基础上,提出基于过零点-极点估计求取IMF瞬时频率、幅度算法,通过对离散信号插值运算精确求取过零点和极点位置,并据此求出相应点的瞬时频率和幅度,最后采用三次样条求取信号的瞬时频率幅度曲线。通过几个典型的例子对该算法进行检验,结果表明,与Hilbert变换结果比较,借助该算法得到信号的时频幅度谱和边际谱结果更精确、频率分辨率更好。     

一种恒幅点频信号的光传输方法

针对恒幅点频信号常用的直接模拟调制光传输和PCM采样数字化光传输方式存在的缺陷,提出一种简单可靠的增量调制数字化恒幅点频信号信号光传输方案,该方案根据采样定理进行增量调制采样,省去直接模拟调制的非线性补偿电路或PCM采样数字化的ADC/DAC转换电路.该方法调试简单,系统可靠,传输距离远,抖动性能指标较好.     

选择性映射算法中的相位序列研究

降低峰值平均功率比是实现正交频分复用(OFDM)系统的一个关键性技术,目前主要有限幅类,编码类和概率类。概率类被认为是一种比较理想的技术,本文研究的选择性映射就是其中的一种。选择性映射需要传输边带信息从而使得频带利用率下降,系统复杂度增加。针对这点对改进的相位序列进行了研究分析,从仿真结果可以得到,这种单极随机相位序列可以有效的降低系统的峰值平均功率比,但是却存在计算量大的缺点。     

改善直接数字合成周期信号频率 分辨率的两种波形序列

在利用直接数字合成方法产生周期性宽带通信对抗背景信号时,信号的频率分辨率、带宽及频谱复杂度直接受限于合成系统的工作频率和存储容量.本文提出两种波形序列,能够在不改变合成系统工作频率和存储容量并且不影响合成信号的幅频包络和基本时域特性的情况下将其频率分辨率提高四倍以上,并且可以提高合成信号的频谱复杂度和可变性.这两种序列还可用于其它高频率分辨率周期信号的直接数字合成.     

一种高稳定性高精度低压差线性稳压器的分析与设计

提出了LDO,其基于缓慢滚降式频率补偿方法,通过在电路中引入三个极零对(极零对的产生没有增加静态功耗),不仅克服了常规LDO不能使用低等效串联电阻、低成本陶瓷输出电容的缺点,而且确保了系统在整个负载和输入电压变化范围内稳定工作.由于LDO通常给高性能模拟电路供电,因此其输出电压精度至关重要;而该补偿方法能满足高环路增益、高单位增益带宽的设计要求,从而大幅提高LDO的精度.该LDO基于0.5μm CMOS工艺实现.后仿结果表明,即使在低压满负载条件下,其开环DC增益仍高于70dB,满载时单位增益带宽可达3MHz,线性调整率和负载调整率分别为27μV/V和3.78μV/mA,过冲和欠冲电压均小于30mV,负载电流为150mA时的漏失电压(dropout电压)仅为120mV.     

Analysis of smooth muscle constants by pole-zero method

The use of pole-zero method for the analysis of smooth muscle network parameters like the myoplasmic resistance, the junctional resistance, and the junctional capacitance is described. The method determines the pole and zero of the equivalent network describing the smooth muscle cells, using the data set obtained from the impedance versus frequency values for tissue strips. The pole-zero method is compared with the frequency response method and the root locus method for the analysis of similar parameters in four strips from guinea pig taenia coli. The values of smooth muscle parameters obtained from all three methods were comparable. The pole-zero method is, however, computationally more efficient and is more precise than the other two methods. The pole-zero method, in determining the smooth muscle parameters, does not deviate from the proposed network model. Furthermore, the pole-zero method does not require phase information as is the case with the root locus method.     

具有快速动态响应的高稳定性电流型降压DC-DC转换器

提出了一种高稳定性的电流型DC-DC转换器.首先应用一种新型的电流型转换器的模型推导了控制环路的增益表达式,在分析其环路增益的基础上,提出了一种新颖的控制环路频率补偿的方法,从而使转换器的稳定性不受负载电流和电源电压变化的影响.其次应用这种新的频率补偿方法,使用0.5μm-CMOS工艺设计了一种电流模式的降压型转换器.仿真结果表明,该稳压器具有高度的稳定特性,其稳定性与负载和电源电压无关.并且由于这种新的频率补偿为环路提供了极高的带宽,所以该转换器具有优异的动态响应.其提供的全负载瞬态响应的建立时间小于5μs,过冲电压小于30mV.     

Speech analysis by pole-zero decomposition of short-time spectra

A new method for representation of speech spectra based on a pole-zero decomposition technique is proposed in this paper. In this method the parameters of a pole-zero model for the smoothed short-time spectrum of speech are determined by adopting a cepstral matching criterion. The cepstral coefficients of the impulse response of the model are equal to the cepstral coefficients of the signal up to a specified number which determine the order of the model system. This is analogous to autocorrelation matching in linear prediction analysis. It is shown that the model spectrum represents both peaks and valleys of the smoothed spectrum equally well, unlike the all pole model of linear prediction analysis where only the peaks are well represented. The pole and zero parameters are derived in an identical manner by approximately deconvolving the pole and zero contributions in the cepstral domain. The residual from the inverse pole-zero system can be used to obtain information about the excitation signal.     

基于频率调制的随机共振系统研究

针对频率调制中存在的门限效应问题,提出了利用非线性科学领域的随机共振原理来降低门限值。首先将接收到的频率调制信号通过一低通滤波器,提取出其中的低频分量,然后输入非线性双稳态系统中,通过调节载波频率,使得系统发生随机共振,多次调节载波频率,可以有效的检测出有用信号的频率。理论分析和仿真结果表明该方法能有效降低频率调制的门限值,并且克服了随机共振不能检测大频率信号的缺点。     

On the non-negative impulse response of multi-dimensional systems

This paper presents sufficient conditions on one-dimensional (1-D) pole-zero patterns that exhibit a non-negative impulse response (NNIR) for several classes of multi-dimensional (M-D) hyper-planar systems in both the continuous-time and the discrete-time domains. The results provide some intuitive ideas about 1-D to M-D variable substitutions that preserve the non-negativity property of impulse response, as well as the relationship between the impulse response of a transformed M-D system and the impulse response of its 1-D prototype. To the best of our knowledge, this is the first paper in the literature discussing the sufficient conditions on pole-zero patterns that guarantee an NNIR for M-D systems. The sufficient conditions on the pole-zero patterns for the employed 1-D prototype systems represent the most inclusive sufficient conditions that ensure an NNIR. As a result, sufficient conditions on the pole-zero patterns that exhibit an NNIR are revealed for a broad category of M-D systems in this paper. It should be noticed that though there is a significant potential of applications in the area of NNIR M-D systems, NNIR M-D system design has received inadequate attention, which is surprising in view of the abundance of design frameworks developed over decades of research in M-D systems. In response to this inadequacy, this paper provides theoretical background and important guidance in constructing NNIR M-D systems. Specifically, the presented results can be employed to construct NNIR M-D filters using M-D hyper-planar filters as the building blocks. The constructing process is illustrated through a simple design example.     

Relationship between frequency response and settling time of operational amplifiers

The effects of pole-zero pairs (doublets) on the frequency response and settling time of operational amplifiers are explored using analytical techniques and computer simulation. It is shown that doublets which produce only minor changes in circuit frequency response can produce major changes in settling time. The importance of doublet spacing and frequency are examined. It is shown that settling time always improves as doublet spacing is reduced whereas the effect of doublet frequency is different for 0.1 and 0.01 percent error bands. Finally it is shown that simple analytical formulas can be used to estimate the influence of frequency doublets on amplifier settling time.     

A frequency sampling filter design method which accounts for finiteword length effects

System functions of frequency sampling filters require pole-zero cancellations on the unit circle. For practical implementations, finite word length effects usually prevent pole-zero cancellations which can result in filter instability. The article develops an optimization method for designing a modified frequency sampling filter which is guaranteed to be stable     

直流力矩电机在机载光电伺服系统中的应用研究

将永磁直流力矩电机引入机载光电伺服控制系统执行机构中可综合实现精度高,体积功耗小等伺服系统性能要求.在对采样电流信号滤波器截止频率的选取规则进行分析论证并给出选择建议的基础上,采用模拟PI电路实现电流闭环,使电流环理论开环特性变为一阶惯性环节,实际闭环截止频率达到1.2kHz.同时在提出一种简单易行的微分实现方法的基础上,将模糊控制引入速度环调节器;由模糊控制 经典零极点配置控制组成的复合控制器使机载光电伺服系统隔离度达到了0.536%,同时阶跃响应的超调为4%.     

一种改进的GFDM时频同步算法

针对广义频分复用( GFDM)系统对符号定时同步要求较高的问题,提出了一种新的基于前缀码的同步算法。在接收端,在获取粗略定时信息的基础上,利用前缀码前后两部分的相位差实现载波频偏估计,并对接收序列的频率偏移进行纠正,然后通过纠正后序列与已知发射前缀的互相关函数实现精确的符号定时估计。由于该前缀码具有共轭对称的特性,使其避免了“平顶效应”的出现。结合5G中低时延高可靠场景,在频率选择性信道中对其进行仿真,并通过均方误差对其性能进行了评估。理论分析及仿真结果表明,该算法相对于原算法具有更好的定时同步性能和更低的复杂度,提升了GFDM系统的整体性能。