一种用于测量厅堂扩声系统动态失真的滤波器

最近,电子工业部第三研究所研制出一套用于厅堂,舞台扩声系统动态失真测量的滤波器。该套仪器由四分之一倍频程带通滤波器和四分之三倍频程带阻滤波器组成。整机采用集成电路元件、有源滤波电路的形式。     

聚合物光学干涉滤波器

在光子产品设计和制造中，聚合物的使用不断地增加。有一类聚合物光学元件仅通过聚合物本身获得产品形状和功能。具体的应用包括超高效率反射器和反射起偏器。最近，已生产出为发展光敏元件产业的全聚合物波长分离滤波器。这些滤波器在元件和设备级别方面为设计者和制造者提供新自由度。     

基于对数域无损积分器的高阶滤波器设计

提出利用双极型晶体管构成的对数域无损积分器以及对数压缩和指数扩展电路实现高阶滤波器.基于无源网络模拟,该设计不仅方法简单,而且使用元件种类很少,易于集成给出一个6阶Butterworth带通滤波器设计实例.PSpice仿真结果表明,该对数域滤波器能在低电压条件下工作,并具有高频、宽调谐范围和低失真等特性.     

跳耦结构差分式连续时间电流模式电流镜滤波器

在差分式电流模式电流镜积分器的基础上，提出了一个跳耦结构差分式连续时间电流模式五阶切比雪夫低通滤皮器的电流镜电路和设计方案。讨论了电流模式跳耦结构滤波器的设计方法，给出了所提出的滤波器电路的设计机仿真结果。该滤波器电路继承了电流镜电路、差分式电路、跳耦结构滤波器的优点，具有适于低电太供电、消除偶次谐波、元件灵敏度低、传递函数失真小等特点。     

SD7408：D类音频功放

杭州士兰微电子发布2×10W模拟输入的D类音频功放SD7408,丰富了公司的音频功放产品线。该电路采用先进的“免滤波器”调制方案,最大限度降低了外部滤波器要求,不仅减少了该电路应用方案的总成本和电路板空间,改进PCB布局,也可以减少因非线性滤波元件而导致的额外失真。该电路可广泛应用于平板电视、多媒体音响等消费音频领域。     

一种具有分段式DEM的二阶噪声整形SAR ADC北大核心

设计了一种具有分段式动态元件匹配(DEM)的高分辨率、低功耗噪声整形SAR ADC。该电路实现了具有无源增益的二阶噪声整形滤波器，从而增强了噪声整形能力。此外，提出了一种分段式动态元件匹配电路来解决由DAC电容失配引起的谐波失真问题，以进一步提高ADC的信噪失真比(SNDR)。仿真结果表明，在4 MS/s的采样速率和40倍过采样率(OSR)的情况下，所设计的噪声整形SAR ADC的信噪失真比达到91.1 dB。当电源电压为1.8 V时，该ADC的功耗仅为231μW,并实现了174.5 dB Schreier优值(FOM)。     

TriQuint发布SAW滤波器p/n 856756

TriQuint半导体公司发布最新的用于GPS（全球定位卫星）导航系统的SAW滤波器p／n 856756，该超低失真、高抗扰的滤波器为客户提供了更多的选择。TriQuint滤波器在对PND用户进行精确定位时，相比其他的无线信号，GPS信号到达地面时其功率水平较低。在接收信号链中的TriQuintSAW滤波器能够滤除非GPS信号源的其他噪音信号，同时降低GPS信号本身的损耗。WWW．triquint．com     

基于Matlab的无失真模拟滤波器设计

介绍用Matlab设计出一个由低通、带阻、相移滤波器构成的无失真模拟滤波器方法.分别给出各个滤波器的设计过程、仿真结果、实际电路图,并在最后给出了经过无失真滤波器后输出信号的眼图.眼图结果表明,无失真滤波器的幅频、相频特性良好.说明用Matlab设计模拟滤波器简单、方便、有效,是一个在滤波器设计方面很有力的工具.     

视频编码失真两步补偿法及其参数描述

为了减少视频编码失真,论文提出了一种新颖的视频编码失真补偿方法两步补偿法。该方法优先补偿解码恢复图像的直流失真,再利用直流补偿后的恢复图像设计维纳滤波器,进一步减弱解码恢复图像中的交流失真。实验数据表明两步补偿法的编码效率优于现有自适应环路滤波方法,提高H.264/AVC的编码效率最高可达26.31%。此外,利用分析得到的交流补偿滤波器系数和为1的特点,提出相应的滤波器系数的量化编码方法,去除了滤波器系数表示方法中的冗余。     

高速接口引发ESD保护元件革新

据意法半导体MPA产品部产品营销科长吉野善晴介绍：“由于设计设备时必须考虑的防ESD措施发生了变化，自2005年秋天起，开发平板电视的技术人员不断表示希望能使用静电电容较低的元件。”由于元件本身的静电电容会导致信号波形失真，因此越来越多的设备设计人员表示，传统的ESD保护元件将会逐渐无法继续使用（见图1）。为了避免信号失真，必须使用静电电容低于现有产品（3pF～5pF）的ESD保护元件。随着对低静电电容ESD保护元件需求的增加，松下电子元器件及意法半导体等器件厂商自2006年起相继推出静电电容低于1pF的ESD保护元件（见表1）。     

Design of a low-distortion 22-kHz fifth-order Bessel filter

A linearity improvement technique employing passive resistors and current-steering MOS transistors as a variable resistance element is proposed to implement a low-distortion filter in CMOS technology. This proposed implementation relies on the linearity of the passive resistors and the tunability of the current-steering MOS transistors operating in the triode region to overcome the limited linearity performance in continuous-time electronically tunable filters. By using the existing systematic feedback loops in the active filters and placing the nonlinear elements inside the feedback, the distortion resulting from the nonlinear devices is greatly reduced by the filter loop gain. A 22-kHz fifth-order Bessel filter, its dynamic range optimized by applying Karmarkar's rescaling algorithm and self-tuned with a switched-capacitor reference resistor, demonstrates better than -90-dB THD with a 2-kHz, 4-V_pp signal in 5-V 2-μm CMOS     

Low-distortion switched-capacitor filter design techniques

The distortion mechanism in switched-capacitor (SC) filters are considered, and closed-form expression relating switched-capacitors filter distortion to circuit parameters are derived. Design techniques for low-distortion applications are discussed and are applied to a sixth-order experimental filter. The filter design uses a fully differential class A/B op amp with a continuous-time common-mode feedback circuit. Distortion measurements show that for 82-dB dynamic range (relative to noise floor) the total harmonic distortion of 0.02% within the whole 4-kHz bandwidth and 0.07% within 20-kHz bandwidth.     

A 2.5-V active low-pass filter using all-n-p-n Gilbert cells with a1-Vp-p range

This paper describes the design and measured results of an all-n-p-n low-voltage (2.5 V), low-current (1 mA), large-swing (1 V_p-p), low-distortion (-53 dB, 1 V_p-p) active filter using a conventional bipolar process. The transconductors for the filter are composed of Gilbert cell transconductors. Distortion has been improved by feedback circuits without increasing the supply voltage and without using p-n-p transistors. The filter is a gyrator-capacitor type third-order Butterworth low-pass filter with a nominal cutoff frequency of 192 kHz. A voltage scaling technique has been applied directly to the gyrator-capacitor filter. This has improved the signal-to-noise ratio by 3 dB. Simulation results indicated that a fast operation up to tens of MHz is possible with a standard bipolar process, as the signal path is composed only of n-p-n transistors     

A 60-mW 200-MHz continuous-time seventh-order linear phase filter with on-chip automatic tuning system

A full CMOS seventh-order linear phase filter based on g/sub m/-C biquads with a -3-dB frequency of 200 MHz is realized in 0.35-/spl mu/m CMOS process. The linear operational transconductance amplifier is based on complementary differential pairs in order to achieve both low-distortion figures and high-frequency operation. The common-mode feedback (CMFB) employed takes advantage of the filter architecture; incorporating the load capacitors into the CMFB loop improves further its phase margin. A very simple automatic tuning system corrects the filter deviations due to process parameter tolerances and temperature variations. The group delay ripple is less than 5% for frequencies up to 300 MHz, while the power consumption is 60 mW. The third-harmonic distortion is less than -44 dB for input signals up to 500 mV/sub pp/. The filter active area is only 900 /spl times/ 200 /spl mu/m/sup 2/. The supply voltages used are /spl plusmn/1.5 V.     

High performance ripple feedback for the buck unity-power-factorrectifier

The buck unity-power-factor rectifier has harmonic-free input current with complete load regulation down to zero output voltage. A new “nonlinear ripple feedback” is proposed which exactly cancels the spoiling effect of DC-side current ripple on the low-distortion AC line current waveforms, even for large amounts of ripple. This cancellation is independent of operating point and readily implemented with analog hardware, thereby permitting economies in the design of the DC filter while maintaining harmonic-free operation. Both large-signal and incremental analyses of the rectifier are given. Confirming experimental results from a 1 kW 48 V isolated battery charger operating with current-ripple levels ranging from 50% to discontinuous-conduction-mode operation are given     

A Monolithic Low-Distortion Low-Loss Silicon-on-Glass Varactor-Tuned Filter With Optimized Biasing

A low-distortion varactor-tuned bandpass filter is demonstrated on a high-Q silicon-on-glass technology. The dc bias network is optimized to achieve high linearity, the center frequency of the filter tunes from 2.4 to 3.5 GHz, and the measured loss of the filter is 2-3 dB at 2 GHz, with a stopband rejection of 25 dB. The measured IIP3 of the filter was +46 dBm     

Restoration of signals degraded by impulse noise by means of a low-distortion non-linear filter

A simple low-distortion non-linear filter for the restoration of signals degraded by random impulsive noise is proposed. It performs considerably better than a median filter, lowering the reproducing error both in mean-square and maximum-error sense, although being comparable in computing time and in terms of storage.     

A 0.6-V 82-dB delta-sigma audio ADC using switched-RC integrators

A 0.6-V 2-2 cascaded audio delta-sigma ADC is described. It uses a resistor-based sampling technique which achieves high linearity and low-voltage operation without subjecting the devices to large terminal voltages. A low-distortion feed-forward topology combined with nonlinear local feedback results in enhanced linearity by reducing the sensitivity to opamp distortion, and allows increased input amplitude, resulting in higher SNDR. The modulator achieves 82-dB dynamic range and 81-dB peak SNDR in the A-weighted audio signal bandwidth with an OSR of 64. The total power consumption of the modulator is 1 mW from a 0.6-V supply. The prototype occupies 2.9 mm/sup 2/ using a 0.35-/spl mu/m CMOS technology.     

一种宽带、低失真、高过载特性的Sigma-Delta模数转换器结构

提出一种混合Sigma-Delta级联调制器结构.结合传统和低失真结构的优点,包括4级:第一级采用二阶多位低失真结构,后面级联传统的一阶调制器.这种结构可以大大减小由于第一级调制器输入信号过大引起的非线性,同时可以较好地抑制带内噪声,因而非常适用于低过采样率和高精度的转换器设计.仿真结果表明,混合Sigma-Delta级联调制器结构具有高的过载特性、节省功耗和芯片面积等优点,适合宽带宽领域的应用.     

An adaptive RAM-DFE for storage channels

A modification of the decision feedback equalizer (DFE), RAM-DFE, is presented and analyzed for use in channels with trailing nonlinear intersymbol interference, especially binary saturation-recording channels. In the RAM-DFE, a look-up table, which can be easily implemented with random access memory, (RAM), replaces the transversal filter feedback section of the DFE. The feedforward section of the equalizer remains linear. A general nonlinear Markov (or finite-state machine) model is used to model the nonlinear intersymbol interference (ISI) channel. With this Markov model, a method is introduced for computing the minimum-mean-squared-error settings of the feedforward filter coefficients and the feedback filter and look-up table contents for the linear DFE and the RAM-DFE, respectively. RAM-DFE with these settings can be significantly better than the linear DFE for channels with trailing nonlinear ISI. Globally convergent gradient-type algorithms for updating the feedforward section coefficients and the contents of the feedback table are introduced and analyzed. Results based on data taken from disk storage units are discussed