Cryogenic ultra-low-noise SiGe transistor amplifier

An ultra-low-noise one-stage SiGe heterojunction bipolar transistor amplifier was designed for cryogenic temperatures and a frequency range of 10 kHz-100 MHz. A noise temperature T(N) ≈ 1.4 K was measured at an ambient temperature of 4.2 K at frequencies between 100 kHz and 100 MHz for a source resistance of ~50 Ω. The voltage gain of the amplifier was 25 dB at a power consumption of 720 μW. The input voltage noise spectral density of the amplifier is about 35 pV/√Hz. The low noise resistance and power consumption makes the amplifier suitable for readout of resistively shunted DC SQUID magnetometers and amplifiers.     

L波段雷达功率放大器设计和优化

设计一种L波段雷达功率放大器.对功率放大器的输出功率、脉冲顶降、热设计等关键参数进行了理论分析,结合电路输出功率的仿真结果对功率放大器的工作效率以及输出功率的带内波动进行评估.研究了脉冲顶降对输出信号的品质影响,探讨了功率放大器热设计的半定量的制约问题.给出系统主要参量的优化设计方法,完成了L波段雷达功率放大器的样机制...     

Thermomechanical noise of a free v-shaped cantilever for atomic-force microscopy

We have calculated the thermal noise of a v-shaped AFM cantilever (Microlever, Type E, Thermomicroscopes) by means of a finite element analysis. The modal shapes of the first 10 eigenmodes are displayed as well as the numerical constants, which are needed for the calibration using the thermal noise method. In the first eigenmode, values for the thermomechanical noise of the z-displacement at 22 degrees C temperature of square root of u2(1) = A/square root of c(cant) and the photodiode signal (normal-force) of S2(1) = A/square root of c(cant) were obtained. The results also indicate a systematic deviation ofthe spectral density of the thermomechanical noise of v-shaped cantilevers as compared to rectangular beam-shaped cantilevers.     

集成运算放大电路噪声谱矩阵计算及噪声性能分析

由于集成运放电路内部具有大量噪声源,特别是运算放大器本身等效输入电压和电流噪声源的相关性,使运放电路噪声分析较困难。常用的噪声功率迭加方法由于无法考虑噪声源相关性会引起较大误差。本文提出用噪声谱矩阵表示具有噪声相关的运算放大器ｅ-ｉ噪声,推导了集成运放电路等效输入噪声谱迭加公式。不仅可以对运放电路的噪声进行准确计算及性能分析,而且可以计算电路内各噪声源的贡献,对低噪声集成运放电路参数设计有重要指导意义。     

A high sensitivity ultralow temperature RF conductance and noise measurement setup

We report on the realization of a high sensitivity RF noise measurement scheme to study small current fluctuations of mesoscopic systems at milli-Kelvin temperatures. The setup relies on the combination of an interferometric amplification scheme and a quarter-wave impedance transformer, allowing the measurement of noise power spectral densities with gigahertz bandwidth up to five orders of magnitude below the amplifier noise floor. We simultaneously measure the high frequency conductance of the sample by derivating a portion of the signal to a microwave homodyne detection. We describe the principle of the setup, as well as its implementation and calibration. Finally, we show that our setup allows to fully characterize a subnanosecond on-demand single electron source. More generally, its sensitivity and bandwidth make it suitable for applications manipulating single charges at GHz frequencies.     

一种微机电源的LDO设计与实现

针对微机电源稳压性能较差的缺点,设计一款输出电压为5 V,最大输出电流为1 A的低压差线性稳压器(LDO)。通过选择误差放大器、反馈电阻网络、大功率N沟道MOS管作为调整管;采用具有过温、限流保护功能的芯片和外围电路构成基准源电路,改善了稳压器的线性调整率。测试结果表明,室温下输入电压为5.5~25 V时,输出电压稳定在5 V,负载为5Ω时电压调整率为0.6%,显示出良好的稳压性能。     

The use of RuO<Subscript>2</Subscript> resistors as broadband low-temperature radiation sensors

The possibility of using commercial RuO₂ planar resistors as low-temperature radiation sensors was investigated. At temperatures of 0.08–0.1 K, their sensitivity to blackbody radiation at temperatures of 5–40 K was about 2–3 pW. The radiation absorption coefficient was <10%. The response is a linear function of the radiation power, thus indicating that the detector band is no narrower than 0.5–2.5 THz. The rise time of an output signal without feedback-assisted temperature stabilization was ~12 s owing to an unexpectedly high thermal capacity of the resistor.     

Noise floor and dynamic range analysis of a microwave attenuation measurement receiver from 50 MHz to 26.5 GHz

The noise floor and dynamic range of a proposed voltage-ratio based microwave attenuation measurement receiver are analysed. The thermal noise and phase noise effect on attenuation measurement is studied. For frequencies higher than 1 GHz, the receiver employs a lock-in amplifier with a coherent frequency reference to minimize the phase noise effect and achieve very wide dynamic range of attenuation measurement. The equivalent noise floor at the receiver mixer output port is found to be around −172 dBm. The dynamic range of the receiver is 181-175 dB from 50 MHz to 26.5 GHz. Measurement results of a 0-170 dB synthesized step attenuator at 26 GHz is given to verify the performance of the proposed receiver.     

Dynamic behavior of amplitude detection Kelvin force microscopy in ultrahigh vacuum

The acquisition rate of all scanning probe imaging techniques with feedback control is limited by the dynamic response of the control loops. Performance criteria are the control loop bandwidth and the output signal noise power spectral density. Depending on the acceptable noise level, it may be necessary to reduce the sampling frequency below the bandwidth of the control loop. In this work, the frequency response of a vacuum Kelvin force microscope with amplitude detection (AM-KFM) using a digital signal processing (DSP) controller is characterized and optimized. Then, the main noise source and its impact on the output signal is identified. A discussion follows on how the system design can be optimized with respect to output noise. Furthermore, the interaction between Kelvin and distance control loop is studied, confirming the beneficial effect of KFM on topography artefact reduction in the frequency domain. The experimental procedure described here can be generalized to other systems and allows to locate the performance limitations.     

激光测距与跟踪系统低噪声电子设计方法

各种电子元器件,光电转换器件存在着各种各样的噪声,如散弹噪声、1/f噪声、热噪声在系统中还存在背景噪声等等.降低噪声,一直是提高系统作用距离的主要研制任务.本文以噪声的基本理论为基础,从工程的角度论证在激光测距与跟踪系统设计中主要的噪声源与低噪声设计方法.并以实例介绍了在工程中应用的前置放大器设计方法.     

A gain and bandwidth enhanced transimpedance preamplifier for Fourier-transform ion cyclotron resonance mass spectrometry

The nature of the ion signal from a 12-T Fourier-transform ion cyclotron resonance mass spectrometer and the electronic noise were studied to further understand the electronic detection limit. At minimal cost, a new transimpedance preamplifier was designed, computer simulated, built, and tested. The preamplifier design pushes the electronic signal-to-noise performance at room temperature to the limit, because of its enhanced tolerance of the capacitance of the detection device, lower intrinsic noise, and larger flat mid-band gain (input current noise spectral density of around 1 pA/√Hz when the transimpedance is about 85 dBΩ). The designed preamplifier has a bandwidth of ~3 kHz to 10 MHz, which corresponds to the mass-to-charge ratio, m/z, of approximately 18 to 61 k at 12 T. The transimpedance and the bandwidth can be easily adjusted by changing the value of passive components. The feedback limitation of the circuit is discussed. With the maximum possible transimpedance of 5.3 MΩ when using an 0402 surface mount resistor, the preamplifier was estimated to be able to detect ~110 charges in a single scan.     

某星载功分器大功率隔离电阻器温控方法研究

针对某星载功分器中的大功率隔离电阻器开展温控方法研究。由于该电阻体积小,热耗大,为了解决高热流密度带来的器件高温失效问题,提出采用金属化过孔、焊锡、涂导热胶等方式来降低主要导热路径的热阻。研究表明,实验结果与计算结果符合良好,通过合理的热设计,可以使电阻器温度在严苛的热环境下保持在85 ℃以内的安全范围。     

LD泵浦腔内倍频Nd:YAG/LBO蓝光473nm激光器的低噪声运转

激光二极管（LD）泵浦腔内倍频Nd:YAG/LBO蓝光473nm激光器在不加入腔内特殊元件的情况下,往往倍频输出功率具有很大的高频噪声,即所谓的“蓝光问题”！这大大限制了473nm蓝色激光的应用！为了降低该激光器件倍频输出功率的高频噪声,采用了通过提高腔内基频光循环强度和缩短激光晶体以减小准三能级激光系统再吸收损耗的方法来实现473nm激光器的低噪声运转！实验中利用两个2W激光二极管耦合作为泵浦源及1.0mm厚的Nd:YAG材料作为激光晶体,在利用10mm长LBO材料作为倍频晶体的情况下,获得了输出功率为195mW的具有低噪声特性的473nm蓝光激光运转！实验结果表明：倍频输出功率（峰－峰值）/平均值小于1%！激光输出在1h内没有发生激光跳变现象发生并且无需腔内其它元件的引入。     

Measuring gain and noise in active long-range surface plasmon-polariton waveguides

We describe techniques and an experimental setup to measure the gain and noise characteristics of a long-range surface plasmon-polariton amplifier consisting of a symmetric metallic stripe waveguide incorporating optically pumped dye molecules in the solution as the gain medium. The setup is capable of acquiring absolute power measurements at the amplifier's output over a narrow optical bandwidth. This allows independent characterization of the amplifier's gain via measurements of stimulated emission and via measurements of amplified spontaneous emission (ASE) over a narrow optical bandwidth, both obtained during the same experimental run. In addition, the absolute power measurements of ASE quantify directly the amplifier's noise.     

Study of thermal and acoustic noise interferences in low stiffness atomic force microscope cantilevers and characterization of their dynamic properties

The atomic force microscope (AFM) is a powerful tool for the measurement of forces at the micro/nano scale when calibrated cantilevers are used. Besides many existing calibration techniques, the thermal calibration is one of the simplest and fastest methods for the dynamic characterization of an AFM cantilever. This method is efficient provided that the Brownian motion (thermal noise) is the most important source of excitation during the calibration process. Otherwise, the value of spring constant is underestimated. This paper investigates noise interference ranges in low stiffness AFM cantilevers taking into account thermal fluctuations and acoustic pressures as two main sources of noise. As a result, a preliminary knowledge about the conditions in which thermal fluctuations and acoustic pressures have closely the same effect on the AFM cantilever (noise interference) is provided with both theoretical and experimental arguments. Consequently, beyond the noise interference range, commercial low stiffness AFM cantilevers are calibrated in two ways: using the thermal noise (in a wide temperature range) and acoustic pressures generated by a loudspeaker. We then demonstrate that acoustic noises can also be used for an efficient characterization and calibration of low stiffness AFM cantilevers. The accuracy of the acoustic characterization is evaluated by comparison with results from the thermal calibration.     

An ultra low noise telecom wavelength free running single photon detector using negative feedback avalanche diode

It is challenging to implement genuine free running single-photon detectors for the 1550 nm wavelength range with simultaneously high detection efficiency (DE), low dark noise, and good time resolution. We report a novel read out system for the signals from a negative feedback avalanche diode (NFAD) [M. A. Itzler, X. Jiang, B. Nyman, and K. Slomkowski, "Quantum sensing and nanophotonic devices VI," Proc. SPIE 7222, 72221K (2009); X. Jiang, M. A. Itzler, K. ODonnell, M. Entwistle, and K. Slomkowski, "Advanced photon counting techniques V," Proc. SPIE 8033, 80330K (2011); M. A. Itzler, X. Jiang, B. M. Onat, and K. Slomkowski, "Quantum sensing and nanophotonic devices VII," Proc. SPIE 7608, 760829 (2010)], which allows useful operation of these devices at a temperature of 193 K and results in very low darkcounts (～100 counts per second (CPS)), good time jitter (～30 ps), and good DE (～10%). We characterized two NFADs with a time-correlation method using photons generated from weak coherent pulses and photon pairs produced by spontaneous parametric down conversion. The inferred detector efficiencies for both types of photon sources agree with each other. The best noise equivalent power of the device is estimated to be 8.1 × 10(-18) W?Hz(-1∕2), more than 10 times better than typical InP/InGaAs single photon avalanche diodes (SPADs) show in free running mode. The afterpulsing probability was found to be less than 0.1% per ns at the optimized operating point. In addition, we studied the performance of an entanglement-based quantum key distribution (QKD) using these detectors and develop a model for the quantum bit error rate that incorporates the afterpulsing coefficients. We verified experimentally that using these NFADs it is feasible to implement QKD over 400 km of telecom fiber. Our NFAD photon detector system is very simple, and is well suited for single-photon applications where ultra-low noise and free-running operation is required, and some afterpulsing can be tolerated.     

探测器光谱灵敏度测试装置

本装置是一多功能光谱测试装置,适用于对红外探测器作宽范围光谱灵敏度的测量,以及红外光源光谱能量分布测量。整个装置由光学系统、电信号处理系统和数据自动记录系统组成。光谱响应的波长范围为1～50μm,在1～10μm波长范围内已校正的波长准确度为±0.1μm,其相对光谱灵敏度分布的重复性为2％。由于采用参比探测器方法组成双光路分光系统,以及锁相放大技术,消除了辐射源光谱分布的选择性和反射及吸收形成的能量损失对测量带来的影响。同时有效地抑制了噪声,提高了系统测试的信噪比,使装置的噪声等效功率达到NEP<7×10~(-11)W/HZ1/2。     

High temperature thermal conductivity of platinum microwire by 3ω method

The 3ω method for thermal conductivity measurement has emerged as an effective technique applicable to micro/nanowires and thin films. This paper describes the adaptation of the method to temperatures as high as 725 K enabling reliable thermal conductivity measurements on such samples for which previously published methods have been found inadequate. In the technique, a sample wire is heated by applying a sinusoidal current at an angular frequency ω, which causes a temperature and resistance variation at an angular frequency, 2ω, leading to a voltage signal at 3ω. The sample is connected as a four-terminal resistor to a digital lock-in amplifier, which is used to detect the in-phase and out-of-phase 3ω voltages resulting from the applied 1ω current. The data are fitted by varying the values of the thermal resistance and diffusion time, both of which are functions of thermal conductivity. Measurements are made at steady state temperatures between 300 and 725 K. Meaningful measurements at elevated temperatures require that thermal losses be understood and minimized. Conduction losses are prevented by suspending the sample above the mounting substrate. Convection losses are minimized by maintaining a vacuum of ~10(-5) torr inside the sample chamber. To minimize radiation losses, an appropriately sized sample is shrouded with a double heat-shield, with the inner shield temperature near that of the sample. Using the 3ω method, the thermal conductivity of platinum was determined to vary between 71.8 and 80.7 Wm(-1) K(-1) over the temperature range of 300 to 725 K, in agreement with published values measured for bulk samples.     

基于STC12C5A60S2单片机的简易电阻测试仪设计

为了实现对微小数值的电阻进行准确和高精度的测量,本文设计了以STC12C5A60S2单片机为核心,利用直流电压源和运算放大器组成一个多值恒流源,实现多量程电阻精确测量。利用单片机内部集成的A/D转换器对被测电阻两端的电压进行采样,通过数值比对,自动控制各个电阻档位继电器的开关,实现量程自动切换功能。用键盘输入筛选电阻阻值及误差值,通过单片机对步进电机的控制来实现电位器阻值的变化,由LCD12864显示测量数据和变化的曲线,符合筛选条件时,系统发出声音提示,实现准确、快速筛选电阻。     

基于AVR单片机的木材含水率测试系统设计

介绍了基于AVR单片机木材含水率测试系统的电路设计、硬件结构及软件设计。并解决了含水率电阻测量法中高阻值电阻难以测量的问题。首先判断电阻的范围,将放大器切换到合适的量程;放大后的电压信号经A/D转换送给AVR单片机计算阻值。经验证,在纤维饱和点以上时,含水率自动测试系统的平均误差小3%;在纤维饱和点以下时,误差小2%,尤其在终含水率（14%～9%）范围内误差小于1%。