Measurement of a filter using a power detector

This paper presents experimental results on the measurement of the magnitude and phase response of RF and baseband signal paths made with a power detector. The frequency response is obtained by measuring the magnitude and phase of the output of the power detector when the forward path is excited by a pair of tones. This technique provides a means for making vector measurements using a scalar detector. Instruments, like network analyzers, commonly use a mixer and sinusoidal source to downconvert the signal for digitization and measurement. The downconversion in this paper is performed using a power detector and an extra tone in the excitation signal itself, drastically reducing hardware complexity. Important applications of this technique include the characterization of the digital-to-antenna path of a software radio and the equalization of the antialiasing filter in a wide-band arbitrary waveform generator. Three examples of measurement, one at low frequency and two others at radio frequencies, show that the errors in the measured response are comparable to those obtained using conventional network analyzers     

Scanning Measurement Method of Dispersion Mini-spot by Quadrant Photodetector

Quadrant photodetector is a new type position detector, which has already been applied to many fields such as measurement, target tracking, control, laser collimation, guidance, etc. System performance is related to laser spot area received by the quadrant photodetector. The optimum linear output signal of system is gotten only when the size of laser dispersion spot is well-proportioned to the detector photosensitive area. A method to measure the mini-spot received by detector and to adjust it in real time is presented, which is based on the quadrant geometrical and optical structure, making use of tilting mirror scanning, the sequence output signal of detector is gotten, then measurement model is built with rate of signal change as characteristic variable, the radius of the laser dispersion spot and adjustable value of dispersion are calculated. The experiment result shows that the maximum error is 0.58μm in measurement range of 0.5mm±0.1mm.     

井下振动数据测量仪器电路设计

本文介绍了使用控制芯片来实现井下振动数据测量,采样参数控制,对振动传感器输出的三个方向波形进行处理,利用硬件电路将其转化为瞬时值、平均值、最大值,并对其九路信号进行采样;同时使电路简单,器件减少,结构紧凑,集成度高,进步提高电路的有效性,有效地降低噪声干扰.     

Low cost video scaler and gray scale integrator

A hybrid digital/analog device capable of making high-resolution linear and area measurements from a standard monochromatic video image is described. The device is capable of dynamic as well as static data acquisition when used in conjunction with standard NTSC video recording equipment. Digital output allows for computer interfacing. Linear dimensions are obtained by electronically superimposing two horizontal and two vertical scaling lines on a video monitor. Each linear dimension has an eight-bit resolution and is displayed on the front panel with seven segment LEDs. Eight-bit, digital-to-analog converters are also used to provide analog outputs. A measurement of the temporal deformation pattern of the accessory capsule surrounding a mechanoreceptor (Pacinian corpuscles) in response to vibratory displacements is demonstrated. Area measurements are obtained via a window comparator, a 6 MHz clock, and a 16-bit digital-to-analog converter. Data is only valid within the zone set by the scaling lines, allowing data regions to be isolated from noise, etc. The 16-bit digital signal measuring the area of interest is then converted for analog output. The measurement of the consensual pupillary reflex in response to full-field illumination (Ganzfeld) is given as an example     

Optical phase difference measurement and correction using AlGaAs integrated guided-wave components

A Y-junction interferometer phase measurement technique that is independent of the power or power ratio in the input arms has been developed. The technique is intended for use in the basic module of a proposed integrated optical system for use at GaAs wavelengths that produces a flat-phase output wavefront. A proof-of-concept AlGaAs guided-wave Mach-Zehnder interferometer was used to demonstrate measurement and correction of a phase difference between the arms using this phase measurement technique. Results have been obtained for the cases of successive steps in the phase difference between the interferometer arms, of random phase differences, and of a power imbalance of up to 30% between the arms.<>     

消光棱镜气室气体检测特性分析

在消光法气体浓度检测中,使用了两个相同的直角棱镜增大透射光束在气体中的光程,利用其对光束的全反射特性提高了气室的检测灵敏度;使用凸透镜对旁轴光束聚焦,解决了二次测量中输出光束平移问题;给出了旁轴光束条件下光束的传输特性方程及灵敏度的定性表达,并对灵敏度进行了仿真分析;使用单波长测量法对气体浓度进行了计算,并分析了系统误差。     

Dimensioning of the Wavelength Converters in a WDM Optical Packet Switch

This paper analyzes the performances of a WDM optical packet switch making use of fiber delay lines to resolve output packet contentions; the optical packet switch is equipped with tunable wavelength converters which can shift optical packets to any wavelength of the output link which they are directed to. As not all packets need conversion, we propose a dimensioning technique allowing to reduce the number of converters and to improve the signal quality by reducing unnecessary conversions. The obtained results show that a remarkable reduction of the number of converters is obtained with respect to that needed by other switches described in literature. Such a saving is achieved by maintaining the packet loss probability below a prefixed threshold.     

V777测试系统DA／AD测试技术的研究

文章以V777测试系统为平台,用虚拟测试方法和DSP的思想来模拟数模混合测试仪的工作机制,包括激励的产生、响应的采集、数据处理和为DUT提供的测试波形的组合响应处理。利用V777测试系统PMU端口可并行测试的功能获取待测电路AD模块的8位输出,在误差允许范围内匹配其理论对应值。在低频下,利用PMU对DA端口模拟信号的输出进行采样,对采样得到的数据做数字信号算法处理,实现波形的判断。用上述方法以低成本来实现具有一定难度的电路的测试。     

Estimation of RF PA Nonlinearities after Cross-correlating Current and Output Voltage

The estimation of 1 dB compression and third-order intercept points can be obtained after the cross-correlation between dynamic current and output voltage of radio frequency power amplifiers. This estimation is performed using actual power measurements and not power inferred from voltage values. The underlining theory and a correlator that allows implementing this measurement on-chip are presented. The trade-off between measuring voltage and the actual power is also discussed and it is shown that different information concerning the output load is obtained when observing the PA’s output voltage and power. Simulation results, obtained with the model of a prototype demonstration chip, show that good accuracy can be obtained with relatively simple measurement conditions. These results include the analysis of optimum stimuli amplitudes and the effect of noise in estimation accuracy.     

高精度低噪声基准电压源的设计

利用反向带隙电压原理,采用基于CMOS阈值电压的自偏置共源共栅电流镜技术,设计了一种低压低噪声基准电压源.该电压基准源没有外加滤波电容的情况下,通过双极型晶体管大的输出阻抗特性,实现了更低的噪声输出,提高了输出电压的精度.Hspice仿真结果表明,在0.95V电源电压下,输出基准电压为233.9 mV,温度系数为7.6...     

A tunable waveguide CO2 laser using Fabry-Perot modulator and fox-smith type mode selector

A tunable waveguide CO₂ laser was constructed and tested. Efficient output was obtained over expanded tuning range making use of the coupling modulation through the F-P modulator. A fox-smith type mode selector was used to obtain the tuning range wider than the longitudinal mode spacing. A continuous tuning range of 2.2GHz was experimentally obtained.     

可调谐半导体激光吸收传感器的温度测量验证

开发了一种可调谐半导体激光吸收传感器,用于测量气体的温度,应用扫描波长吸收谱和固定波长调制谱探测水蒸气在7 454.4 cm-1和7 185.6 cm-1附近的两条吸收谱线。传感器可实现绝对温度测量,固定波长调制谱更可实现10 kHz以上的测量带宽。传感器的性能和精度在已知温度和压力的静室中进行测量验证,在600~1 000 K的设定温度范围,两种方法的测量误差（RMS）都小于2%。表明可调谐半导体激光吸收光谱（TDLAS）传感器对于均匀的流场具有快速和精确的温度测量能力。     

用于梳状结构光学测速系统的周期优化方法

为了提高梳状结构光学测速系统的测速精度,采用数学原理研究了梳状结构的间距大小对输出光强信号周期性的影响,通过优化输出光强信号的周期性来提高测速精度,并采用一种结合图像处理选择最佳间距的实验方法,进行了相关的理论分析,对两种不同路面进行了实验仿真验证,得到不同间距下不同的输出光强信号的周期性情况。结果表明,当栅状结构的间距大小与地面特征点大小一致时,得到的输出光强周期性最优,对于普通的柏油和水泥路面,对应到地面的最佳栅状结构间距大小为1.0mm ~1.5mm。     

一种有效的短序列功率谱估计算法及其应用

由于实际中采集到的数据量总是有限的，所以要准确获得待研究数据的特性必须采用高效的短序列估计方法。本文提出了一种基于伯格算法的新的短序列谱估计方法，该方法在阶数估计时引入收敛因子，从而更为有效地估计了阶数；同时不直接用伯格算法计算反射系数，而是先求得二阶预测误差系数，继而求一阶反射系数，再进一步求得高阶系数来实现谱估计。计算机仿真表明，这种算法可以有效地减小谱偏，提高谱分辨率。     

A high gain, high output saturation power Pr/sup 3+/-doped fluoride fiber amplifier operating at 1.3 mu m

A high net gain of 30.1 dB at 1.309 mu m and an output saturation of 13 dBm are obtained using a Pr/sup 3+/-doped fluoride fiber amplifier pumped at 1.017 mu m. The critical Pr/sup 3+/ concentration at which concentration quenching begins to occur was obtained by fluorescence lifetime measurement. The Pr/sup 3+/ concentration should be less than 1000 ppm to suppress the concentration quenching by cross relaxation. A high signal output power of 17.8 dBm was extracted from the Pr/sup 3+/-doped fluoride fiber. The Pr/sup 3+/-doped fluoride amplifier shows good potential for use in 13. mu m telecommunication systems.<>     

Bandstop Filter in Nonradiative Dielectric Waveguide Using Rectangular Resonators

A bandstop filter realized by means of rectangular resonators coupled to the center dielectric strip of a nonradiative dielectric (NRD) waveguide is described.This filter has the advantage that it is simple to manufacture, making use of a center dielectric of standard cross section. The design procedure is similar to the conventional strip line design procedure, with the stubs replaced by "stubs" of dielectric, or resonators. The design equations for the stub coupling are derived the properties of the stubs are obtained through measurement.     

An alternative method for spectral response measurements of large‐area thin‐film photovoltaic modules

A new method for the spectral response measurement of large‐area single and multi‐junction thin‐film photovoltaic modules is presented, making use of a chopped monochromatic beam produced from a continuous source with band pass filters and lock‐in technique. The beam is projected onto part of the test module and superimposed over continuous bias light of variable colour. The procedure for the determination of the absolute spectral response is presented, and the influence of the intrinsic non‐uniformity of the monochromatic beam is investigated. The results obtained are compared with those from two other methods of spectral response measurement, providing a validation of the proposed experimental setup. Copyright © 2011 John Wiley & Sons, Ltd.     

基于UC3842开关稳压电源的设计

开关电源是一种效率很高的电源变换电路,通过对Boost型开关电源作详细的数学推导后得到准确数据。该系统包括整流滤波模块、DC-DC变换模块、过流保护及人机接口模块,以DC-DC变换器作系统的核心。采用UC3842作开关电源控制芯片,开关管采用耐高压,导通电阻很小的MOSFET管IRF640。输出滤波电路中用LC构成的型网络,同时输出采用单片机采样系统,可显示当前的电流和电压,且通过采样电流实现过流保护功能。     

Matched filter estimation of serial blood vessel diameters from video images

A method for making a contiguous series of blood vessel diameter estimates from digitized images is proposed. It makes use of a vessel intensity profile model based on the vessel geometry and the physics of the imaging process, providing estimates of far greater accuracy than previously obtained. A variety of techniques are used to reduce the computational demand. The method includes the generation of measurement estimation error, which is important in determining total vessel patency as well as providing a basic measure of diameter estimate accuracy.