微弱信号检测的前置放大电路设计

针对精准农业中对微弱信号检测的技术需求,论文设计了以电流电压转换器,仪表放大器和低通滤波器为主要结构的微弱信号检测前置放大电路.结合微弱信号的特点讨论了电路中噪声的抑制和隔离,提出了电路元件的选择方法与电路设计中降低噪声干扰的注意事项.本文利用集成程控增益仪表放大器PGA202设计了微弱信号检测前置放大电路,并利用微弱低额信号进行了测试,得到了理想的效果.     

一种用于微机测控系统的高性能检测信号转换变送器

介绍了一种用于微机系统的高性能检测信号隔离放大器。具体阐述了将传感器低电平信号放大为微机系统使用的高电平信号的隔离放大器。较详细地讨论了隔离放大器前置级和电压/电流转换电路的设计。     

HgCdTe红外探测器放大电路的低噪声设计

以HgCdTe光伏型红外探测器输出的微弱电流信号为根据对探测器的发前置放大电路和二级放大电路进行设计,运用标准的电路理论建立了等效噪声模型,分析计算电路中各个噪声源引起的噪声,进而运用叠加法计算总的电路的噪声和信噪比可知所设计放大器电路为高增益、低噪声、高信噪比放大电路,最后从工程角度提出了抑制电路噪声的方法.     

一种检测微弱光电流信号的锁相放大器设计

针对强背景噪声下光寻址电位传感器中微弱电流信号检测困难的问题,设计了一种基于锁相放大原理的微弱光电流信号检测电路。该电路主要包括两部分：前置放大器和相敏检波器;其中,前置放大器主要由包括第一级电流电压转换电路在内的四级放大电路组成。系统选用高性能的AD8652作为前置放大器中的第一级运放,相敏检波器采用电子开关型芯片AD630实现信号的乘法运算。实验结果表明,当前置放大器增益设置为104、105、106时,整个锁相放大器检测系统的灵敏度分别为-1.2678×104V/A、-1.2651×105V/A、-1.2302×106V/A,该灵敏度与理论计算值的相对误差绝对值最大为3.38%,可检测的输入电流范围是100nA~180μA,频率响应范围是1kHz~1.2MHz;当外加白噪声时,系统输出值随着噪声的增大而增大,当噪声不超过待测信号的2.25倍时,系统输出值与无噪声的输出值之间的相对误差不超过5%。系统具有良好的稳定性和线性度,在微光电流信号检测中具有较好的应用前景。     

基于PI闭环控制的AMR磁阻传感器信号调理电路

为了提高磁场测量精度,提出一种基于PI闭环控制的AMR磁阻传感器信号调理电路。该电路由前置放大器、开关同步检波、积分电路和闭环反馈电路组成。首先通过选取较小的前置放大器增益,以降低对传感器输出噪声的放大;然后利用积分器对放大后信号进行积分,得到积分电压;最后,将积分电压进行V/I转换,并将电流接入HMC1001偏置电流带,实现闭环反馈,以抵消外部待测磁场,当电路平衡时,传感器工作于零场,积分输出电压正比于待测磁场。与开环结构对比实验结果表明:在相同的灵敏度条件下,闭环式信号调理电路噪声功率谱密度为40 pT/√ Hz @1 Hz,并且与开环式的信号调理电路相比,它的输出信号信噪比提高了15.55 dB。     

有关光电检测技术中的一个放大性电路的设计

光电检测技术是一个电子技术与光学技术紧密结合在一起的一个新兴的检测技术,具有二者的优点,在光电光电检测系统中光电器件紧密连接一个低噪声前置放大器,它的任务是:放大光电探测器件所输出的微弱电信号;匹配后置处理电路与探测器件之间的阻抗。对前置放大器的要求是:低噪声、高增益、低输出阻抗、足够的信号带宽和负载能力,以及良好的线性和抗干扰能力。针对不同类型的光电检测系统的相应的前置放大电路的种类不同有T型网络前置放大电路、差分式前置放大电路、双运放前置放大电路、高阻型前置放大电路,低阻型前置放大电路等等。     

一种改进的差动放大电路

<正> 在微弱信号检测电路中,由传感器送出伴有干扰的弱信号,通常需经一个前置放大器放大后,方可送往后级处理。由于差动放大器对共模噪声信号有良好的抑制能力,故前置放大一般由差动放大器来承担。一般差动放大器电路如图1所示。在理想情况下,当R_1=R_3,R_1=R_2时,     

程控增益射频宽带放大器

为实现射频信号的放大和程控增益调节功能,采用压控增益宽带放大器AD8367为核心放大器件,通过MSP430F5529单片机控制高精度数/模转换器TLV5638实现增益步进调节。前置放大级采用低噪声宽带放大器OPA847,功率输出级采用高速电流反馈宽带放大器THS3201,实现10MHz~110MHz宽带、增益调节范围为12~52d B、步进1d B的射频宽带放大器。     

一种双色激光接收放大电路设计

为了实现对双色激光探测器的光电信号转换和处理,设计一种高增益光学接收电路.采用前置放大器和主放大器两部分放大电路,使用多级放大器级联,通过优化各级放大器的放大倍数和级间匹配,实现高增益放大,并转换为差分信号,实现与后级模数转换器件的匹配.通过对接收电路的测试表明,可以有效输出稳定的高增益高信噪比双色信号,实现前放100倍、主放56 dB的放大和差分信号输出.     

一种增益自适应光电信号放大器

该文设计了一种针对光电信号的可自动调控增益的微弱电流信号放大器,该放大器使用电压比较电路与数字逻辑电路结合。电压比较电路对将输入的电压信号与设定的三个基准电压进行比较,再使用数字逻辑电路对比较结果进行处理得到增益选择信号,实现了电路根据输入信号的幅值自动选择放大增益。实验表明,该放大器可以将不同幅值的电流信号按照电路选择的增益放大到适合AD采集的幅值范围。     

A novel integrated silicon capacitive microphone-floating electrode“electret” microphone (FEEM)

A novel principle “electret” microphone, i.e., floating electrode electret microphone, is proposed and implemented in this study. Single-chip fabrication and corrugation technique are used in the design and fabrication of the microphone. The floating electrode is encapsulated by highly insulated materials to ensure that there is no electric-leakage passage between the floating electrode and the electrodes of the microphone. Net-free electronic charges (not “bonded” charges as in traditional electret) in the floating electrode can excite the electric field, which is similar to that of the traditional electret. The floating electrode can be easily charged by use of the “hot” electron technique, available using the avalanche breakdown of the p⁺-n junction. Therefore, the electret microphone is rechargeable, which can greatly increase the lifetime of the device. The preamplifier has been on-chip integrated in a junction-field-effect transistor (JFET) source-follower type with resistors by use of ion implantation. Electret charges are banded in a deep potential trap, thus, this microphone can operate at a high temperature (as high as 300°C) and has high stability and reliability. Experiments show that the prototype has a 3-mV/Pa sensitivity and a larger than 21-kHz frequency bandwidth in a 1 mm ×1-mm diaphragm area. Microphone performance can be further improved by optimized process and design. The fabrication is completely integrated-circuit (IC) compatible, hence, the microphone shows promise in integrated acoustic systems     

微传声器的发展􀀂 与光纤传声器

根据目前国际上传声器的生产情况和发展趋势,结合ECM讨论硅基微型传声器的结构特性,并分析国内生产现状以及它们在生产上的优势和欠缺.联系豪恩公司的生产特色和产品结构,介绍其在进行的技术改革和开展的产品,生产技术,市场开拓,发展远景等方向的科学研究而进行的战略性投资的情况.文中具体介绍驻极体话筒,数字话筒,光纤话筒等传声器的原理,结构性能和与高校合作,开发具有竟争力有高技术含量的硅基驻极体话筒、光纤话筒和数字传声器.这也表明豪恩公司在短期内为把自己建设成为电声,光声生产技术基地和开发成为有特色、有竟争力、有高科技含量的传声器生产研究中心而做的努力.     

High-performance condenser microphone with fully integrated CMOSamplifier and DC-DC voltage converter

The development of a capacitive microphone with an integrated detection circuit is described. The condenser microphone is made by micromachining of polyimide on silicon. Therefore, the structure can be realized by postprocessing on substrates containing integrated circuits (IC's), independently of the IC process, integrated microphones with excellent performances have been realized on a CMOS substrate containing dc-dc voltage converters and preamplifiers. The measured sensitivity of the integrated condenser microphone was 10 mV/Pa, and the equivalent noise level (ENL) was 27 dB(A) re. 20 μPa for a power supply voltage of 1.9 V, which was measured with no bias voltage applied to the microphone. Furthermore, a back chamber of infinite volume was used in all reported measurements and simulations     

非共振光声CO_2气体检测系统

非共振光声红外气体检测系统结构简单、成本低,有很好的应用前景。设计和制备了基于MEMS电调制光源、驻极体麦克风和单腔室及双腔室非共振光声探测器的气体检测系统。根据系统的频率响应特性选择了最佳的光源调制频率,并对不同体积分数的CO2气体进行了测试。相对于传统的单腔室结构,设计的双腔室结构有效提高了系统的响应信号幅值,并降低了气体检测限,单腔室系统的检测限约为7.2×10-6,双腔室系统的检测限约为2.1×10-6。     

A low-power self-biased rail-to-rail preamplifier as a readout circuit for a capacitor-type microphone

This study is dedicated to design a readout circuit to extract the output signal of a capacitive-type MEMS microphone. A low-power preamplifier is forged for a capacitive-type microphone to meet the demands on cell phone applications. The design starts with modeling the electro-mechanical behavior of a biased capacitive-type microphone using combination of AV and DC voltages sources. This aims to enable co-simulation of the microphone and the readout circuit design. The output signal of a capacitance-to-voltage converter is normally small and may cause substantial noise in the output signals. Therefore, a preamplifier is designed and applied to amplify the signal to an acceptable level for the convenience of ensuing signal processing. The designed readout circuit consists of two main sub-circuits, responsible for functions in two different stages. One is a newly-designed self-bias circuit in the structure of a capacitance-to-voltage converter at the first stage, while another is a low-voltage low-power two-stage or rail-to-rail MOS operational amplifier at the second stage. The proposed circuit is implemented by using the technology of TSMC 0.35 µm Mixed-Signal MODE (2P4M, 3.3 V/5 V) POLYCIDE. The supply voltage is fixed at low voltage (3 V), the total power dissipation is merely 200 μW. Experiments are finally conducted to validate the performance of the designed readout circuit from 20 to 20k Hz with appropriate add-on high- and low-pass filters.     

Silicon condenser microphones with corrugated silicon oxide/nitride electret membranes

Corrugated electret membranes are used in a micromachined silicon microphone. The membranes consist of a permanently corona-charged double layer of silicon dioxide and silicon nitride, known to have excellent charge-storing properties. This electret can replace the external bias needed for condenser microphones. The well-known LOCOS technique—also combined with dry etching—is used for the first time to fabricate membranes with corrugation depths of several microns. The membrane thickness amounts to 600 nm.

The interferometrically measured center deflection is up to 40 nm/Pa for diaphragms with four corrugations of up to 3.3 μm depth and a size of A_M=1 mm². This high mechanical sensitivity limits the dynamic range to sound pressures below 50 Pa. The obtained mechanical sensitivities are in excellent agreement with the theory.

The most compliant corrugated diaphragms result in a microphone sensitivity of 2.9 mV/Pa, an equivalent noise level of 39 dB(A) and a total harmonic distortion below 1.7% at 28 Pa (123 dB SPL). The corrugation depth in the sensors has been only 1.3 μm. All sensors cover the whole audio and low ultrasonic range. The temperature coefficient is between 0.05 and 0.1 dB/K.     

基于ZigBee无线传输技术的电子听诊器

设计一种基于ZigBee无线传输技术的实用电子听诊器,能够采集和处理人体心音数据,并将处理后的数据通过无线传输方式发送出去,接收端通过USB通信接口将数据传输到上位机进行实时显示.该设计运用MEMS麦克风采集心音信号,前置放大和滤波端提供信号放大和滤波等调理功能.无线传输模块采用TI公司的集成无线收发芯片CC2530.     

一种电流模式敏感放大器及其在SRAM的应用

电流模式敏感放大器是提高大容量SRAM性能的有效方法.介绍了在SRAM中应用传统的电流模式敏感放大器设计,在现阶段研究的基础上提出了一种用数据线来跟踪位线的电流模式敏感放大器设计.用HSPICE进行电路级模拟,得出结果正确.相比较以前的电路设计,速度提高46.3%,功耗延时积降低38.13%.     

A lightweight sensing method of tooth-touch sound for disabled person using remote controller

To support disabled people to use remote controllers, several biological signals are used. The tooth-touch is one of desirable biological signals. This is because it is the simple and natural human behavior. However, a sophisticated signal processing to extract only the tooth-touch sound is needed since the tooth-touch sound is mixed with the voice sound. This paper proposes a lightweight sensing method extracting the tooth-touch without a sophisticated signal processing to eliminate only voice sound from the sound wave in which tooth-touch and voice are mixed. Instead of the audible sound wave, proposal uses a shock wave (i.e., ultrasonic wave) which is generated when the upper tooth and the lower tooth hit each other. Using the shock wave generated to detect the tooth-touch, a trivial high-pass filter can eliminate only voice sound in the lower frequency domain than in the ultrasonic domain including the tooth-touch. Through a preliminary experiment that uses a conventional microphone and well-known digital high-pass filter, we show that the used electret microphone can sense the tooth-touch as ultrasonic wave and the high-pass filter can extract only tooth-touch. Then, we show some robustness of our method by using the sound waves including the voice and tooth-touch. In addition, we design the filtering hardware to implement a small and cheap system-on-chip achieving a real-time operation. Through the implementation of Field Programmable Gate Array, and the simulation, we show that our hardware is small and performs well for a real-time operation.     

电容式仿生触须传感器的设计与试验

为模拟动物触须所具有的非常敏锐的环境感知能力,设计了一种电容式仿生触须传感器并开展试验研究。该传感器以电容式微音器为敏感元件,以光纤为触须材料,用以测量作用在触须尖端的微弱刺激信号。讨论了触须传感器的工作原理,进行了传感器结构和信号调理电路设计,分析了传感器特性。试验研究表明:该仿生触须传感器具有良好的重复性、静态特性和线性度,能充分反映被扫描物体的表面特征,可用于物体形态和表面纹理的有效识别及机器人自主运动避障。