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1.
设计了一种含有量程自动转换功能的3 1/2位的数字电容表。系统以AT89S52单片机为控制核心,以电容充电规律为测量依据,实现了对0~2μF范围内的电容值的测量。电容表的量程分为4档,通过单片机控制移位寄存器实现对测量档位的自动选择控制,读数单位采用nF,可显示小数点。在Proteus软件环境下进行了系统设计的仿真测试,仿真结果表明,电容表在有效范围内能实现电容值的自动准确测量,得到了预期的结果。  相似文献   

2.
利用中芯国际(SMIC)0.18μmCMOS工艺设计了应用于高速率光接收机的前置放大器.该放大器采用了RGC放大器的电路拓扑结构,应用了优化的片上螺旋电感,通过并联峰化技术实现了带宽放大.仿真结果表明跨阻放大器的跨阻增益为52.8dB·Ω,-3dB带宽为8.6GHz,1.8V单电源供电功耗小于37mW.  相似文献   

3.
为了提高电化学分析系统的分析速度和测量的准确度.探究如何对电化学分析系统中,既有慢变化又有快变化的pA~μA范围的微电流进行快速、准确的测量.基于定阻式I/V转换的方法,对pA~μA范围的微电流,设置了由微机控制的多个电流量程及自动调零电路,以及从软、硬件上进行抗工频干扰的设计.实现对宽范围微电流测量的量程快速搜索、转...  相似文献   

4.
导电聚苯胺/γ-Fe2O3纳米复合物的红外与微波吸收性能   总被引:1,自引:0,他引:1  
用溶胶-凝胶法制备了γ-Fe2O3纳米粉料,然后通过原位聚合方法制备了质子酸掺杂的聚苯胺(PANI)/γ-Fe2O3纳米复合材料.对其形貌、微结构以及电导率分别用X射线衍射仪(XRD)、透射电镜(TEM)和四探针法进行了表征,用矢量网络分析仪和傅立叶红外谱仪(FTIR)测试分析了样品的微波、红外吸收特性.发现PANI/ 5 wt% γ-Fe2O3复合材料在7~18GHz频率范围内最大反射式吸波衰减为-25dB, 吸波衰减小于-8dB的有效带宽为4.6GHz,比未复合的导电聚苯胺和纳米γ-Fe2O3材料具有更优越的微波吸收性能,但随着γ-Fe2O3的含量分别增加到10%和20% 时,复合物的带宽变窄,微波吸收性能下降;另外,PANI/ 5wt% γ-Fe2O3复合物与纳米γ-Fe2O3材料以及导电聚苯胺相比,红外吸收特性得到了显著增强,在3276cm-1波数附近的透过率仅为17%、1700cm-1 ~1100cm-1范围内透过率均小于40%.同时对PANI/γ-Fe2O3纳米复合材料的微波和红外吸收机理进行了初步探讨.  相似文献   

5.
采用双复纤维作为吸收剂,在基体环氧树脂中平行、垂直、正交排列,制备出了吸波复合材料。分别研究了平行、垂直和正交排布双复纤维的微波吸收特性,并对双复纤维的吸波机理和吸波性能的影响因素作了初步探讨。结果表明:双复纤维的吸波性能不仅与碳纤维含量有关,还与双复纤维在基体中的排列方式有关,当双复纤维平行排布、含量为0.5%(质量分数)时,复合吸波材料最大反射衰减为-27.3dB,低于-5dB的有效带宽为3.2GHz;当双复纤维垂直排布时其吸波性能不明显;当双复纤维正交排布、含量为1%(质量分数)时,吸波复合材料最大反射衰减为-29.3dB,低于-5dB的有效带宽为3.6GHz。  相似文献   

6.
龚玲莉  陈开和 《电器评介》2013,(12):122-123
本系统采用AVR单片机作为系统的核心,由数据采集模块、存储模块、控制模块、按键及LCD显示模块等组成,该系统实现了将示波器和逻辑分析仪集成在一起,其中示波器部分最高采样频率可达60MSa/s,垂直灵敏度从5V/div到10mV/div共9挡,水平扫描速度从50ms/div到250ns/div共8挡,逻辑分析部分为16通道,最高采样频率为10MSa/s,利用多CPU技术在LCD上显示信号。  相似文献   

7.
《电工技术》2002,(2):55
福禄克公司新推出的187、189万用表在性能、量程和准确度等方面实现了大突破:(1)0.025%的基本直流准确度;(2)50000字高分辨力显示模式,并带有瞬时读数的详细分析,模拟指针,双层背景光;(3)100kHz交流带宽、dBm/dBV测量,有效值电压电流测量;(4)响应速度有了显著的提高;(5)更宽的量程,高阻值测量达500MΩ,电导量程达500ns;  相似文献   

8.
针对检测设备的限制导致不能使用不同频率的大电流对大量程霍尔电流传感器的带宽进行测试的问题,设计一种带宽检测电路并探究大量程霍尔电流传感器的带宽与测试电流大小的关系。通过带宽检测电路将直流大电流斩波可以得到不同频率的大量程脉冲测试电流,该测试电流流经霍尔电流传感器和康铜丝阵列。根据-3 dB原则比较霍尔电流传感器输出信号幅值相对康铜丝阵列的失真程度,确定霍尔电流传感器的带宽。使用30~100 A不同大小测试电流对霍尔电流传感器的带宽进行测试,结果表明测试电流大小不同,大量程霍尔电流传感器的带宽不同,且随着测试电流的增大,带宽逐渐减小。  相似文献   

9.
为了满足电化学分析系统中宽量程范围内微电流的准确测量需求,设计了一种新型低功耗宽量程精密恒电位仪,提出了基于补偿式恒电位控制与两级比例电阻法相结合的微电流检测方法,实现10~(-10)~10~(-3)A量程范围内的准确电流测量。文中给出新型低功耗宽量程精密恒电位仪的硬件电路设计,利用等效模型电路推导了电路传输特性,并采用自制的三电极自制针状传感器和高精度电阻模拟生物电化学分析过程。仿真和实测结果表明,新型低功耗宽量程精密恒电位仪信号输出稳定,在10~(-10)~10~(-3)A量程范围内的微电流检测相对误差小于1%,据此设计的便携式恒电位仪已实际应用于组织工程液压生物反应器智能化监测系统。  相似文献   

10.
锌合金拉链头压铸自动生产线由锌合金熔化、自动加料系统、压铸及分料系统、自动回炉送料系统等部分构成,采用PID控制实现熔炉温度的可调可控,基于S7-300和S7-200构建无线以太网PLC控制系统实现自动加料控制,采用共用一套PLC的一体化控制方法实现压铸和分料的控制,基于Omron CJ2M和CP1E构建RS232无线通信PLC控制系统实现自动回炉送料控制,并采用基于机位的动态优先级算法实现了加料和回炉送料系统中运料任务的选取。应用结果表明,按所述方法实现的拉链头压铸全自动生产流水线,完全能够达到按需实时均衡送料,且系统维护方便,可靠性高。  相似文献   

11.
以高纯度的Y2O3、Fe2O3为原料,用固相反应法制备Y3FesO12( YIG)材料,通过VSM、SEM、Agilent 4291B对材料样品进行分析、测试.结果表明,所制备的YIG材料介电常数大约为15,饱和磁化强度μ0Ms约180mT.基于该材料设计环行器,利用Ansoft HFSS仿真软件建立三维电磁场仿真模型...  相似文献   

12.
The first integrated sampled-grating distributed Bragg reflector (SGDBR) laser-semiconductor optical amplifier-Mach-Zehnder modulator transmitter is presented. Devices have 3 dB bandwidth ranging from 13-18 GHz corresponding to electrodes lengths that range between 200-300 /spl mu/m long. This corresponds to a V/sub pi/ of 4.8-6.2 V.  相似文献   

13.
Electrical activity in the brain spans a wide range of spatial and temporal scales, requiring simultaneous recording of multiple modalities of neurophysiological signals in order to capture various aspects of brain state dynamics. Here, we present a 16-channel neural interface integrated circuit fabricated in a 0.5 mum 3M2P CMOS process for selective digital acquisition of biopotentials across the spectrum of neural signal modalities in the brain, ranging from single spike action potentials to local field potentials (LFP), electrocorticograms (ECoG), and electroencephalograms (EEG). Each channel is composed of a tunable bandwidth, fixed gain front-end amplifier and a programmable gain/resolution continuous-time incremental DeltaSigma analog-to-digital converter (ADC). A two-stage topology for the front-end voltage amplifier with capacitive feedback offers independent tuning of the amplifier bandpass frequency corners, and attains a noise efficiency factor (NEF) of 2.9 at 8.2 kHz bandwidth for spike recording, and a NEF of 3.2 at 140 Hz bandwidth for EEG recording. The amplifier has a measured midband gain of 39.6 dB, frequency response from 0.2 Hz to 8.2 kHz, and an input-referred noise of 1.94 muV rms while drawing 12.2 muA of current from a 3.3 V supply. The lower and higher cutoff frequencies of the bandpass filter are adjustable from 0.2 to 94 Hz and 140 Hz to 8.2 kHz, respectively. At 10-bit resolution, the ADC has an SNDR of 56 dB while consuming 76 muW power. Time-modulation feedback in the ADC offers programmable digital gain (1-4096) for auto-ranging, further improving the dynamic range and linearity of the ADC. Experimental recordings with the system show spike signals in rat somatosensory cortex as well as alpha EEG activity in a human subject.  相似文献   

14.

Objective

To reduce acoustic noise levels in T 1-weighted and proton-density-weighted turbo spin-echo (TSE) sequences, which typically reach acoustic noise levels up to 100 dB(A) in clinical practice.

Materials and methods

Five acoustic noise reduction strategies were combined: (1) gradient ramps and shapes were changed from trapezoidal to triangular, (2) variable-encoding-time imaging was implemented to relax the phase-encoding gradient timing, (3) RF pulses were adapted to avoid the need for reversing the polarity of the slice-rewinding gradient, (4) readout bandwidth was increased to provide more time for gradient activity on other axes, (5) the number of slices per TR was reduced to limit the total gradient activity per unit time. We evaluated the influence of each measure on the acoustic noise level, and conducted in vivo measurements on a healthy volunteer. Sound recordings were taken for comparison.

Results

An overall acoustic noise reduction of up to 16.8 dB(A) was obtained by the proposed strategies (1–4) and the acquisition of half the number of slices per TR only. Image quality in terms of SNR and CNR was found to be preserved.

Conclusions

The proposed measures in this study allowed a threefold reduction in the acoustic perception of T 1-weighted and proton-density-weighted TSE sequences compared to a standard TSE-acquisition. This could be achieved without visible degradation of image quality, showing the potential to improve patient comfort and scan acceptability.
  相似文献   

15.
We developed high-speed optoelectronics packaging technologies for a waveguide photodiode and a traveling wave electro-absorption modulator device for 40-Gb/s digital communication systems. The effects of the device and the packaging designs on the broadband performance were investigated to optimize broadband characteristics. For the receiver, inductive peaking was used for bandwidth control and an internal bias tee was implemented; in addition, two types of preamplifier devices were used to develop high-gain receiver and wide-bandwidth receiver. In the optical-to-electrical response, a 3-dB bandwidth of the high-gain module was about 32 GHz as compared to 42 GHz for the wide-bandwidth module. The clear 40-Gb/s nonreturn-to-zero (NRZ) eye diagrams showed a good system applicability of these modules. In addition, an optimized modulator module showed a 3-dB bandwidth of 38 GHz in the electrical-to-optical response, an electrical return loss of less than 10 dB at up to 26 GHz, an rms jitter of 1.832 ps, and an extinction ratio of 5.38 dB in a 40-Gb/s NRZ eye diagram.  相似文献   

16.
提出了一种新型串行馈电的全向缝隙阵列天线,在带状线两侧背靠背刻蚀8对圆环缝隙,在缝隙内部加载一个Y形缝隙,延长Y形缝隙的长,并在顶部刻蚀横槽,形成最终的Y-T型缝隙结构,用以提升单元辐射性能。采用遗传算法(GA)对阵列进一步优化,使其工作带宽进一步扩宽,增益有所提升。根据设计结果加工制作了天线样品,实际测试表明,天线的|S11|<-10 dB阻抗带宽为7.93% (5.56~6.02 GHz),带宽内峰值增益均高于8.99 dBi。工作在5.8 GHz处,E面旁瓣水平低于-10.11 dB,峰值增益为9.43 dBi, 且有稳定的全向辐射性能。  相似文献   

17.
A high SNDR discrete-time (DT) 2-1 MASH sigma-delta modulator (SDM) for 15-MHz bandwidth was presented. Cascade of integrators with feedforward (CIFF) scheme, combined with the optimized gain coefficients, was adopted to avoid of the integrators. Double sampling technique was employed to relax the OPA settling requirements by halving the clock frequency and therefore reduce the power consumption. Five-bit flash quantizer was adopted in both stages to improve the overall signal-to-noise and distortion ratio (SNDR) performance, and third-order dynamic element matching (DEM) was analyzed and applied for the multibit DACs to suppress the element mismatch noise. Fabricated in a mature 0.18-μm CMOS technology, the occupied area of the modulator was 0.24 mm2 and dissipation power 25.4 mW from a 1.8-V voltage supply. As a sampling rate of 240 MHz for the input sampling and DAC and 480 MHz for the flash ADC, a SNDR of 90.2 dB over 15-MHz signal bandwidth and the corresponding effective number of bits (ENOB) of 14.69 bit were achieved. The spurious-free dynamic range (SFDR) was 98 dB with DEM turned on for a 3.75 MHz at −2.5-dBFS input signal, and the figure of merit (FOM) was 30.7 fJ/conv. for 15-MHz bandwidth. A 15-MHz bandwidth multibit MASH2-1 discrete-time sigma-delta modulator was proposed. Double sampling technique was employed to relax the OPA settling requirements by halving the clock frequency and therefore reduce the power consumption. High-order DEM was analyzed and applied for the multibit DACs to suppress the element mismatch noise. Fabricated by a 0.18-μm CMOS process, the modulator achieved a SNDR of 90.2 dB and the corresponding ENOB 14.69 bit over 15-MHz signal bandwidth. The proposed modulator was very suitable for wideband applications including wireless communication systems, high-frequency biomedical imaging or sensing systems, and so on.  相似文献   

18.
This paper describes an ultralow-power neural recording amplifier. The amplifier appears to be the lowest power and most energy-efficient neural recording amplifier reported to date. We describe low-noise design techniques that help the neural amplifier achieve input-referred noise that is near the theoretical limit of any amplifier using a differential pair as an input stage. Since neural amplifiers must include differential input pairs in practice to allow robust rejection of common-mode and power supply noise, our design appears to be near the optimum allowed by theory. The bandwidth of the amplifier can be adjusted for recording either neural spikes or local field potentials (LFPs). When configured for recording neural spikes, the amplifier yielded a midband gain of 40.8 dB and a -3-dB bandwidth from 45 Hz to 5.32 kHz; the amplifier's input-referred noise was measured to be 3.06 muVrms while consuming 7.56 muW of power from a 2.8-V supply corresponding to a noise efficiency factor (NEF) of 2.67 with the theoretical limit being 2.02. When configured for recording LFPs, the amplifier achieved a midband gain of 40.9 dB and a -3-dB bandwidth from 392 mHz to 295 Hz; the input-referred noise was 1.66 muVrms while consuming 2.08 muW from a 2.8-V supply corresponding to an NEF of 3.21. The amplifier was fabricated in AMI's 0.5-mum CMOS process and occupies 0.16 mm2 of chip area. We obtained successful recordings of action potentials from the robust nucleus of the arcopallium (RA) of an anesthesized zebra finch brain with the amplifier. Our experimental measurements of the amplifier's performance including its noise were in good accord with theory and circuit simulations.  相似文献   

19.
针对一种两轴四音圈电机驱动的快速反射镜,提出了一种驱动控制方法。该方法为每个电机配置一个高带宽的电流环,通过控制电流给定量的符号和大小,实现同一轴上两台电机的同步推挽运动;为了改善系统阻尼,抑制谐振,提高响应频率,基于快速傅里叶变换(FFT)谱分析的方法,精确测量了快速反射镜传递函数,并引入一个双二阶型校正函数,对快速反射镜的开环响应特性进行改善。实际测试结果表明:快速反射镜高达20 d B的谐振峰得到有效抑制,-3 d B响应带宽由校正前的118 Hz提高到177 Hz,稳定时间由原来的151 ms降低到3.5 ms,超调量由原来的83.3%降低到1.51%,快速反射镜的动态响应得到明显改善,证明了该方法的有效性。  相似文献   

20.
用铁砂(磁铁矿)尾矿制备的复合电波吸收材料特性   总被引:3,自引:0,他引:3  
用铁砂(磁铁矿)尾矿为原料可制备性能优良的电波吸收材料。在8 ̄12GHz,其最大吸收量达18dB,匹配厚度0.58mm,10dB带宽2.5GHz。铁砂尾矿经450℃淬火处理后最大吸收量可提高到28.4dB;用尖晶石型铁氧体吸收材料代替部分尾矿可使吸收峰位置移向宽3.5GHz;不同电性介质加入,也能改善其吸收特性,差异较大,尾矿用于生产吸波材料,变废为宝,有较高的经济效益。  相似文献   

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