一类网络环境下的离散线性系统的可靠性滤波器设计研究

 本文对一类网络环境下的离散线性系统进行了可靠性滤波器设计,其中用一组随机变量来表示传感器的概率性失真,并综合考虑网络环境的时滞、错序、丢包等非理想服务质量,建立了包含传感器随机失真的系统模型;通过使用李亚普诺夫泛函稳定性理论和线性矩阵不等式技术给出了可靠性滤波器设计算法存在可行解的充分性条件,最后通过数值算例验证本文给出方法的有效性.     

一种适合集成传感器的微弱信号读出放大器

设计了一种适用于低频集成传感器微弱信号检测的低噪声放大器。该电路应用斩波技术抑制低频噪声和失调，利用带通滤波器减少残余失调电压。电路采用0．8μm N阱CMOS工艺设计，并进行了实际流片。对试制样片进行了测试，测得电路的增益为37dB，等效输入噪声为56．4nV/√Hz。     

一种高线性度低失真跨导运算放大器的设计

为了解决线性跨导输入范围有限的问题,提出了一种具有宽线性输入范围的高线性运算跨导放大器(Operational Transconductance Amplifier,OTA),可有效适用于包括低频连续时间滤波器在内的电流模式电路。该OTA利用源极退化和辅助差分结构,通过减少失真分量来显著增加线性范围。此外还利用该OTA实现了一种二阶全差分滤波器;采用SCL180 nm CMOS工艺进行了设计和仿真。实验结果表明,相比于其他设计方法,该OTA和滤波器具有更宽的线性范围和更低的失真。对于1 MHz信号频率、600 mVP-P的输入,该OTA的三次谐波失真分量和互调失真分量分别为-74.8 dB和-76.1 dB,线性范围为0.9V(1%跨导变化)。对于300 mVP-P、10 kHz输入,该滤波器的三次谐波失真分量和互调失真分量分别为-69.75 dB和-65.2 dB。     

传感器的低频特性对高冲击测试的影响研究

根据航天、航空环境中加速度的测试特点,对比分析了压电传感器和压阻传感器在高冲击环境下的测试性能。首先,通过对冲击信号进行建模,仿真分析了不同低频特性的加速度传感器对冲击信号测试的影响;然后,分析了压电、压阻类传感器的低频特性;最后,用冲击试验台验证压电传感器和压阻传感器在模拟的环境下的测试情况,得出低频特性好的传感器(压阻传感器)更适合在高冲击条件下的测量的结论。     

某型过载传感器数据采集失真故障原因研究

本文对某型过载传感器试验中数据采集失真的故障原因进行了分析。基于阻尼对传感器动态特性的影响分析可得出,传感器在被试件的载荷急剧变化时会产生系统振动,若频率达到传感器的固有频率,将会导致传感器的数据采集失真。     

线性相位数字化音调控制

本文提出了一个新的线性相位三路滤波器系统,该系统实现了数字化音调控制。这种滤波器系数的数值大约有80%都等于零,其余的非零系数的数值分别等于0.5和0.25。因此,这个滤波器系统实质上不用乘法。当高频增益量和低频增益量为1时,这个滤波器系统是无频率响应失真的纯延时系统。     

MOEMS低频声传感器的设计与实验研究

MOEMS声传感器是MEMS技术、微光学技术、声传感技术相结合发展的新一代声音传感技术,具有灵敏度高、抗电磁场和射频干扰等优点。针对水下潜艇对空声预警涉及的高灵敏度、低频响应好、微型化声传感器整列,研究了反射光强度调制型MOEMS低频声传感阵元。对MOEMS低频声传感器膜片的振动特性进行了有限元分析,得出振动膜片的几何参数,并对反射光强特性进行了仿真和实验。采用设计的MEMS膜片、850 nm波长的LED光源设计并制作了MOEMS低频声传感器样机,通过实验表明,该传感器低频响应好,灵敏度可达200 mV/     

光学磁场传感器中超宽带模拟信号的重构

为了解决光学脉冲磁场传感器中超宽带模拟光信号的数据采集与波形重构,本文提出了一种基于频带分割与频谱搬移的模拟信号重构方法。在频域上采用分割滤波器进行频带分割,在每个采样通道内对输入的子带信号进行采样,降低了对ADC采样速率的要求,再由各个通道的采样序列重构原模拟信号。该方法有效解决了光学磁场传感器中带宽高达几千兆赫的信号无法直接进行A/D转换的难题。给出了重构算法并进行了计算机仿真。仿真结果证实,滤波器的特性决定了重构的精度。所提出的方法具有较高的信号重构精度和较小的频谱失真。     

焊接工艺的改进

介绍了压电角速率传感器用敏感元件的焊接及密封工艺的改进。采用新工艺后，敏感元件的成本降低，可靠性提高及性能得到了改善。将该工艺应用到低频滤波器用谐振子中，同样得到了满意的结果。     

应用于微传感器信号处理系统的低通滤波器的设计与实现

研究旨在设计一款应用于微型飞行器机翼表面分离点检测的高精度微型传感器信号处理系统中的模拟低通滤波器。该滤波器由开关电容滤波器及其前置抗混叠滤波器和后置平滑滤波器组成。在整个信号处理系统中,滤波器不仅起到滤除信号干扰和噪声的作用,而且还用作过采样模数转换器的前置抗混叠滤波器。设计基于无锡上华0.5um 2层多晶硅3层金属（2P3M）CMOS 工艺,在3.3V电源电压下,采用相关双采样技术（CDS）及优化的开关组合,削弱了器件非理想特性的影响,提高了开关电容滤波器的精度,并运用具有低元件灵敏度及失真特性的多重反馈型二阶低通滤波器作为抗混叠滤波器和平滑滤波器,保证了整个滤波器具有良好的高频衰减特性。芯片测试结果表明：该芯片的截止频率为0.7kHz, 面积为0.39 mm2,功耗仅为1.53mW。     

Envelope-constrained filters with uncertain input

In an envelope-constrained filtering problem with uncertain input the set of possible input waveforms and the set of permissible output waveforms are each defined by envelope constraints (time domain inequalities). The object is to find the optimal (minimal norm) inpulse response for which every waveform in the input envelope evokes a response in the output envelope. The problem is solved by extending earlier results for a single specified input. The solution is further extended to allow for unknown-but-bounded errors in the filter realization.Research supported by the CSIRO and the Australian Research Grants Committee.Part of this work was carried out while the first author was at the Control and Management Systems Division of Cambridge University, UK.     

极化有源雷达校准器的幅相失真分析及修正

极化有源雷达校准器（Polarimetric Active Radar Calibrator,PARC）可用于宽带高分辨雷达的定标,以使高分辨成像技术能准确刻画雷达目标的细微特征,但其作为有源器件会引入额外失真从而影响系统失真补偿。本文基于成对回波理论及频域失真补偿原理,通过将频域补偿转换为时域滤波,提出截取滤波器系数的方法以修正PARC失真。实测数据结果表明了理论分析和提出的修正方法的正确性,修正后的PARC可近似理想地补偿系统失真。     

对FIR数字滤波器频域实现错误观点的讨论

关于FIR数字滤波器的频域实现存在一种错误的观点和做法,即直接在离散傅利叶变换域将输入信号属于阻带的谱线清零,而属于通带的谱线保留,再离散傅利叶反变换到时域,并且认为通过这种方法得到的信号是对输入信号理想滤波的结果.本文针对这一观点,利用频域取样的概念,从时域和频域两个角度分析,指出该做法并不能实现理想滤波,并且滤波性能通常不能达到指标要求.     

Non-idealities Compensation in Full-Digital Receivers with Application to Ultra-Wide Band

Nowadays many transceivers adhere to full-digital design principles, with the basic operations performed in the analog domain (filtering, down-conversion) and the whole remaining processing postponed to the digital domain (including matched filtering and synchronization). Though the operations in the analog front-end are ideally reversible, hence no signal degradation should occur before the analog-to-digital conversion (thus preserving the information integrity), however the intrinsic non-idealities in the circuitry may introduce a certain level of distortion. In this paper we provide a simple and flexible approach for the compensation of these effects. We derive useful formulas for obtaining a digital compensation filter by means of a direct transformation of the analog system coefficients. This allows to easily perform the compensation in the digital domain via fast Fourier transform. To illustrate the procedure, the case-study of a ultra-wide band receiver is addressed. Numerical results show that an improvement of more than 1 dB can be obtained at bit-error rate of interest for the applications. Sample code is also provided for an easy implementation.     

Power converter line synchronization using a discrete Fourier transform (DFT) based on a variable sample rate

Line synchronization of grid connected power converters is a well recognized problem when the grid is weak, or derives from a remote area power supply with poor frequency regulation. Such systems can suffer significant line voltage distortion due to notches caused by power device switching and/or low frequency harmonic content, which can easily corrupt the output of a conventional zero crossing detector. This paper presents a method of filtering the incoming grid voltage using a recursive discrete Fourier transform (DFT). The filter provides a high degree of noise immunity but does produce a phase shift between the incoming grid voltage and the filtered output voltage when the DFT time window does not match the grid period. Two methods of compensating this phase shift are presented, based on tracking the drift in the phase predicted by the recursive DFT. The first method makes a deadbeat adjustment to the time window (thereby changing the sampling rate) while the second approach calculates the phase error based on the linear phase response of the DFT. These compensation algorithms can correct for discrepancies of at least 25% between the DFT time window and the system period, and can track grid frequencies with slew rates as high as 40 Hz/s with negligible phase shift (<2/spl deg/) between the grid voltage input and the filtered output waveforms.     

Harmonic filtering of high-power 12-pulse rectifier loads with aselective hybrid filter system

Current distortion of 12-pulse rectifier loads is significantly lower compared to six-pulse rectifier loads. However, in passive filtering of the lowest and dominant characteristic 11th and 13th harmonics, the use of 5th and 7th filters is often required in order to prevent possible parallel and series resonance between the passive filter and source impedance which can be excited by source background distortion or by load current residual noncharacteristic harmonics at the 5th and 7th harmonic frequencies. In hybrid filter systems, an active filter (AF) can be added in series with the passive filter in order to isolate the source and load. In most proposed hybrid filter systems, AF control is based on the detection of total current distortion and high-frequency inverters. With a selective AF control system and voltage-controlled inverter, the AF can be controlled to isolate the load at the critical frequencies only while at all other frequencies the passive filter function is preserved so that lower switching frequency and AF rating is required. In this paper, the authors present a selective AF filter control system and simple hybrid filter topology suitable for the compensation of high-power 12-pulse rectifier loads. Harmonic current controllers based on the second-order infinite-impulse response digital resonant filters are used, as they can be considered as simple digital algorithms for more complex double cascaded synchronous-reference-frame-based proportional plus integral controllers. They are centered to the targeted harmonic frequencies by using an adaptive fundamental frequency tracking filter. This approach gives good results, even if the reference waveform (in our case, a load voltage) is highly distorted or unbalanced and no separate phaselocked loop is required. Test results for a laboratory model of this system and stability analysis are presented and the importance of delay-time compensation is discussed     

具有宽调谐范围的低电压对数域二阶低通滤波器

提出了一个由BiCMOS构成的对数域二阶低通滤波器,并采用跨导线性原理分析得到其传递函数。分析了晶体管的寄生电容对此滤波器频率特性的影响。PSpice仿真结果表明,该对数域低通二阶节的实际频率特性和理想特性基本一致。且具有宽频率调谐范围、低工作电压和低失真等特点,可用于对数域高阶滤波器的设计。     

一种图像脉冲噪声小波域广义滤波算法

提出了一种脉冲噪声滤波算法.首先对噪声图像进行二维小波分解,得到高频和低频子图像;其次对高频子图像序列采用改进自适应加权中值滤波进行处理,以排除水平、垂直、对角方向的噪声;然后对于低频子图像引入基于修正系数的维纳滤波进行处理,并进行小波系数重构;最后设计出一种小波域图像增强模型,通过设置调节系数,将图像分为不同区域分别进行相应比例的对比度拉伸处理,结合实验定量讨论了噪声强度与模型系数的函数关系.实验表明,该滤波算法不仅优于几类单一滤波算法,相对于某些组合滤波算法而言,也具有一定的优势.     

Vers les 20 kbit/s en transmission décamétrique ionosphérique : une application du traitement d’antenne sur des capteurs colocalisés

This paper presents an operational system of digital transmission within the h.f. frequency range, aiming at a significant increase of the data transfer rate compared with the current standard (4800 bit/s). Therefore, an array processing algorithm performs with a set of collocated sensors, the spatial responses of which are different one from each other. The dependence of the incoming polarization relatively to the direction of arrival induces a significant decorrelation of the received signals though no geometrical phase exists. Signal processing techniques run at the output of the spatial filter resorting for the synchronisation and the filtering (lms algorithm) to classical and well-tested techniques involving training sequences. An experimental radio link with a 250 km range has been set up to test the sensibility of the performances in reception regarding the choice of waveforms. The operational results reach the expected goal as the data transfer rate increases up to 20 kbit/s in a bandwidth of 6 kHz.     

数字图像模糊滤波盲取证算法

数字图像模糊滤波操作常用于美化润饰“伪造”图像.针对常用的均值滤波、空域高斯低通滤波与中值滤波,提出了一种能同时检测上述3种操作的盲取证算法.首先将高频残差作为特征提取域,然后分别基于二值局部模式LBP和自回归模型提取特征,最后使用支持向量机构造模糊滤波检测器.实验结果表明,所提算法能有效地检测模糊滤波操作,对抗JPEG压缩的鲁棒性能较好.