Multisection optical parametric–Raman hybrid amplifier for terabit+ WDM systems

We demonstrate flat-gain wide bandwidth Raman-Fiber optical parametric hybrid amplifier for wavelength division multiplexed systems (WDM). Raman-parametric amplifiers exploit system non-linearities which are otherwise inevitable in evolving WDM systems. Investigations show that the pumps of parametric amplifier and Raman amplifier can be carefully selected at wavelengths, to give gain over complementary bandwidth regions, resulting in wide bandwidth with low gain ripple. Results show a flat gain of 24.3 dB for 12 × 100 Gbps WDM system with lowest ripple of less than 2.78 dB reported over 220 nm bandwidth for Raman-FOPA hybrid.     

The Design of Extremely Low-Noise Camera-Tube Preamplifiers

The design of current amplifiers suitable for amplifying the signal of camera tubes (or other similar transducers) is presented. Excellent noise performance can be obtained especially at low frequencies. Only one adjustment is required for shaping the frequency response and a very large bandwidth can be obtained. Experimental results are given for an amplifier designed for a camera tube with 15-pF output capacitance. The measured equivalent input noise current of this amplifier is smaller than 1 nA in a 5-MHz frequency band. The bandwidth of the amplifier exceeds 10 MHz.     

一种计算热计量仪表误差的简便方法

热计量仪表中各组成部分的准确度对其热量计量准确度起着至关重要的作用。目前的有关标准与规程只给出了热计量仪表误差极限的计算方法 ,并由此确定其准确度等级。实际上 ,热计量仪表的误差并不是其各部分组件误差的代数和。文中根据热计量仪表误差计算的基本方法 ,提出了一种计算热计量仪表准确度的简化法 ,具有一定的准确性 ,便于在实际测量中使用     

传导抗扰度测试的信号电平控制方法

通过对传导抗扰度测试的信号电平控制方法进行分析,表明功率放大器增益的不确定度会导致试验电平的误差。为了避免功率放大器增益所引起的误差影响,对信号电平的控制方法提出改进。通过监测功率放大器的输出功率,调整输出信号的大小,提高传导抗扰度测试的准确性。     

Further Analysis of the Modulated Subcarrier Technique of Attenuation Measurement

The modulated subcarrier technique of attenuation measurement offers an accurate and convenient means of calibrating rotary vane attenuators. The technique also presents the possibility of being extended to other types of attenuation measurement. This paper gives an analysis of the output of the microwave detector, assuming it is completely linear; an error analysis of the technique; and a comparison of the technique with the 30-Mc IF substitution technique of attenuation measurement.     

Recursive random-sampling strategy for a digital wattmeter

A recursive random-sampling strategy is proposed for the implementation of a digital broadband wattmeter. In this strategy each sampling instant is obtained by adding to the preceding one a predetermined constant lag plus a random increment. In order to correlate the measurement uncertainty to the bandwidth, the asymptotic mean-square error arising from the sampling strategy and the filtering algorithm is evaluated and analyzed; it has been shown that the proposed sampling strategy does not limit the bandwidth of the instrument if an appropriate statistical distribution of the random increments is selected. The theoretical results are compared with those obtained by simulating the measurement process     

基于数字频谱与模拟带通滤波组的两线制涡街流量计

基于MSP430F1611单片机,采用数字频谱分析与模拟带通滤波器组相结合的方式,研制新型两线制数字涡街流量计,以扩展量程比,保证现场测量精度,并实现低功耗工作,解决目前此类流量计存在的关键性技术问题。采用低功耗运放和数字电位器组成程控放大器,以适应涡街传感器输出信号强度较大范围的变化;根据少点数FFT计算结果,选择带通滤波器组,既满足涡街传感器信号频率范围变化大的需要,又对涡街信号进行最佳滤波;设计有效的电源管理模块和电流输出电路,为仪表两线制工作提供足够的电流。     

Basic characteristics of quantum paramagnetic amplifiers

Conclusions It is advisable to consider as basic those characteristics of a maser whose aggregate completely determines the properties of a maser in its practical application (as an amplifying stage in a receiving system), and whose values can be measured directly. Such characteristics include the amplifier frequency range, amplifier gain, bandwidth, noise temperature at the amplifier input, saturation power, gain instability, and decoupling. Another group of characteristics which can be measured directly is of no particular interest, and includes the restoration time and losses of the amplifier.Finally, a third group of characteristics which are of specific interest and can be determined unambiguously, provided the characteristics of the first two groups are known, includes the paramagnetic amplification factor, resonant maser efficiency, and maser sensitivity and dynamic range.     

Field Programmable Analog Arrays for Conditioning Ultrasonic Sensors

This paper proposes the use of field programmable analog arrays (FPAAs) as adaptive conditioning blocks for ultrasonic sensors. The uncertainty achievable through this technique, in fact, results very sensitive to the measurement conditions, due to the attenuation affecting the echo during its propagation. Indeed, FPAAs emulate analog circuits whose characteristics have to be dynamically tuned according to different operating conditions. Actually, the signal provided by the ultrasonic sensor is properly processed in order to improve the overall measurement accuracy. In this paper, the prototype of a distance meter based on time-of-flight (TOF) measurement is presented in order to evidence the advantages gained by FPAA features in processing the sensor output to compensate echo attenuation and distortion versus target distance. The prototype working is supervised by a digital signal controller (DSC) whose tasks are: 1) driving the ultrasonic transducer; 2) performing the echo acquisition; 3) tuning on the fly the FPAA features; 4) evaluating the TOF; 5) measuring the target distance; and 6) delivering the final result to the end user. This paper is completed by the results achieved in a number of experimental tests allowing interesting considerations to be drawn. In particular, the experiments confirm the prototype reliability and effectiveness also with ultrasonic echoes characterized by very low signal-to-noise ratios.     

Bridge Circuit for Measuring Differences of Current or Voltage from a Preselected Value

A bridge circuit has been developed, using a Zener diode, which enables measurement of small changes in current or voltage from a preselected value. The circuit features increased sensitivity over a meter whose range includes the total current and is more easily used than a balanced bridge or potentiometer. The design equations are developed and the design procedure outlined for both the current and voltage difference measuring bridges, while a sample calculation is made for the current change measuring circuit. A bridge similar to that in the sample calculation was built and tested. The test circuit displayed less than 1 per cent nonlinearity of meter current vs change of input current for the design region of 460±5 ma. This shift was attributed to a slight heating of the Zener diode or a resistor at the higher test currents, but since the diode used in the test circuit had a smaller power rating than the type originally intended for use, it is not considered to be a serious limitation.     

Performance analysis of BER optimization in WDM systems using EDFA

Wavelength division multiplexing (WDM) systems, which are widely used in telecommunication, have the advantages of huge bandwidth support and reliability. A performance analysis is presented of a WDM system using an erbium-doped fiber amplifier (EDFA), with specific emphasis on bit error rate (BER) optimization. EDFA parameters, including doped fiber length and pump power, are optimized and performance evaluating parameters for different modulation schemes are observed. Simulation results provide optimized BER, noise figure, and gain flatness values. The WDM system is modeled from 1546 nm to 1558 nm bandwidth to obtain maximum gain uniformity, low noise figure, and low BER. This wavelength range is selected to investigate the 1550 nm wavelength commonly used in the telecommunication industry. Also, that we are using a WDM grid, so multiple channels can be accommodated in this range.     

端度类量具接触法测量的要点

狭义上的端度类量具,多指量块。而在光学机械量仪中,端度类测量仪器是指测量两端面外尺寸的量块、量具或零件的仪器,如测长机、测长仪、光学计等。所以广义上的端度类量具可以指凡是以量具两端面外尺寸为使用尺寸的量具,包括量块、量棒、内径千分尺、套管尺塞尺等。在测量各类端度类量具时,往往选择用端度类光学仪器来直接读出被测量具的偏差。测量时,要根据被测量具两端不同的测量面,选择合适的测头测帽,并寻找正确的转折点,以减少接触法测量中的测量误差。该文总结了各类端度类量具测量中遇到的测头选择问题和相应转折点的寻找方法。     

双向电能表的检定

介绍双向单相电能表和双向无功电能表检定时应注意的事项,提出减小双向单相电能表正、反向计量误差变化的办法,指出现有的电能表检定装置检定双向无功电能表时存在的不足及其解决方法。     

静水拖曳法电磁流速仪校准方法

利用搭建的高精度静水拖曳法流速标准装置,对JFE公司ACM3-RS电磁流速仪的流速测量能力进行了实验研究。考察了该流速仪的零点特性,以拖车车速为标准测试了不同速度下流速仪的示值误差,并分析了不同入水深度对测量结果的影响。实验结果表明,流速低于1600mm/s时该流速仪具有良好的线性和重复性,示值误差能够优于2%或5m/s,在流速更高时需重新标定;该流速仪存在明显的零点漂移现象,实际应用中需及时修正;淹没深度对流速仪测量结果有明显影响,建议应用前考虑实际淹没深度进行校准。     

Experimental 1-V flexible-IF CMOS analoguebaseband chain for IEEE 802.11a/b/g WLAN receivers

A low-voltage low-power analogue-baseband chain designed for IEEE 802.11a/b/g wireless local-area network (WLAN) receivers is described. It features architecturally a 'two-step channel selection' to complement the radio front-end, and a flexible intermediate frequency (IF) reception capability to alleviate the cancellation of frequency and DC-offset. In circuit implementation, a double-quadrature downconverter based on a 'series-switching' mixer- quad realises a wideband-accurate I/Q demodulation. A 'switched-current-resistor' programmable-gain amplifier (PGA) minimises the bandwidth variation and transient in gain tuning by stabilising, concurrently, the PGA's feedback factor and quiescent-operating point. An 'inside-OpAmp' DC-offset canceller creates area-efficiently a very low cut-off frequency high-pass pole at DC while providing a fast settling of DC-offset transients. Fabricated in a 0.35 mum complementary metal-oxide semiconductor (CMOS) process without resorting to any specialised device, the prototype consumes 14 mW per channel at 1 V. The transient time in a 52-dB gain step is < 1 mus and the stopband rejection ratio at 20/40 MHz is 32/90 dB. The error vector magnitudes are -27 and -17 dB for 802.11a/g and b modes, respectively.     

Four Voltmeter Vector Impedance Meter Based on Virtual Instrumentation

In this paper, a digital vector impedance half-bridge meter based on virtual instruments is designed, implemented and tested. Here, not only the accuracy of the magnitude of the impedance is considered but, more importantly, its phase measurement accuracy. The meter utilizes a four-voltmeter method which is a basic modification of the well-known three-voltmeter method. The half-bridge is constructed with commercially available data acquisition (DAQ) board in the form of peripheral control interconnect cards incorporated in personal computers. The DAQ board is used only to acquire the voltages instead of using four separate voltmeters, while the excitation signal is produced by an integrated circuit signal generator. The main error in this method arises from the error in measuring the voltage values. Since the resolution of the DAQ board used here is 16 bits; expect that absolute errors due to A/D conversion will be around 0.305 mV for ±10 V range. Detailed error analysis of the method is included in the context of the paper. It is found that the errors in the impedance magnitude is fairly small and relatively less sensitive on the resolution of the voltmeters because of the relative measurements in the half bridge with a precise reference resistance. The original three voltmeter vector impedance meter has relatively large error in the phase especially in the small phase angles. To decrease the phase error to an acceptable range, one has to increase the resolution of the voltmeter appreciably, which makes them expensive. The other solution to reduce the error in the phase angle with less cost is to add a fourth voltmeter which acquires directly the small phase angles. In this case, it is found that, a much lower resolution voltmeter can be utilized while achieving an acceptable measurement accuracy of the impedance.     

The problem of analyzing errors in measuring systems

Summary In the operation of a linear measuring system with its elements subjected to various random external disturbances which produce in the elements additional static errors, transmitted to the output of the system together with the basic errors of the elements, a total static error is produced at the output. The latter error is the one which determines the accuracy of the measuring system under given conditions.If in experimental work the required variable is measured several times by means of a measuring system, whose elements are subjected to various random external disturbances, a statistical analysis of the measurement results may produce a certain compensation of the static measurement errors of this variable.     

Design of Relaxation Oscillator Based Ultra-wideband SFQ Amplifier for Chip to Chip Interconnection

In Rapid Signal Flux Quantum (RSFQ) logic circuits, on-chip interconnects and multichip module implementations for nearby distances have already been established. However, the flexible interconnection of two distant chips is still not achieved reliably due to impedance mismatching and attenuation. In this work, we propose a circuit that allows the usage of Passive Transmission Lines (PTLs) to transfer single-flux-quantum (SFQ) pulses between two distant chips which are separated by a distance greater than 10 cm by using 50 ?? transmission lines. For this purpose, we design an SFQ amplifier circuit to deal with impedance mismatch and attenuation problems. The circuit consists of two main parts: a relaxation oscillator (RO) circuit and an impedance transformer. The RO circuit utilizes relaxation oscillations occur in the underdamped Josephson junctions. The impedance matching circuit is an 8-section Chebyshev quarter-wave transformer and it eliminates impedance mismatching problem between the amplifier circuit and PTL. We performed circuit simulations and obtained voltage amplitude of about 600 ??V at the output of the circuit. The transformer has a broadband impedance matching with a fractional bandwidth (ratio of the bandwidth of a device to its central frequency) of 1.4 and a maximum Voltage Standing Wave Ratio (VSWR, the maximum voltage divided by minimum voltage on the transmission line) of 1.5.     

AVR 单片机在油耗测量中的应用

介绍一种AVR单片机串行通讯在汽车油耗测量中的应用方法．此方法能够将测量结果通过软件控制以数字信号的方式传送给主控单片机．减小了远距离传输的信号衰减和外界干扰．十分适合用于汽车油耗的测量．配合标准容积的油箱使用．测量精度达到了0．1％～0.5％．     

光纤中基于SBS实现慢光的数值研究

通过运用带有预测.校正的隐格式有限差分法对基于光纤的受激布里渊散射耦合方程组进行了数值求解.在增益0～16范围内考察了布里渊增益系数、增益带宽以及有效模面积对时间延迟和脉冲展宽的影响.结果表明,较小的增益系数和增益带宽、较大的有效模面积使得Stokes信号具有更大的饱和增益值,相应的时间延迟也较大.在固定泵浦功率并保证增益参数在小信号范围的情况下,时间延迟及脉冲展宽因子随着增益系数的增加而增加,但随着增益带宽以及有效模面积的增加而减少.