低温低噪声放大器的发展概况及其结构设计综述

介绍了低温低噪声放大器的研制历史、现状及应用情况 ,举例分析了在该类放大器的结构设计中需要解决的关键技术 ,对军事和民用装备的有关领域有参考作用。     

Precision Resonator Microwave Spectroscopy in Millimeter and Submillimeter Range

By the use of Fabry–Perot resonator with quality factor 600 000 and fast precision (down to one Hertz) frequency control of coherent millimeterwave radiation source the 20 Hz accuracy in measurements of the width of resonance curve is obtained. This accuracy corresponds to the detection of 1.8 × 10^–3 dB/km absorption in the sample filling the resonator and exceeds the before known sensitivity more than by an order of magnitude. The example of precise measurement of 60 GHz oxygen absorption band in the real atmosphere is presented. The new possibilities of application of precision resonator microwave spectroscopy to the atmospheric problems as well as to the ultra-low absorptions measurements in dielectrics and metal surfaces up to Terahertz frequencies are discussed.     

A Low Noise NbTiN-Based 850 GHz SIS Receiver for the Caltech Submillimeter Observatory

We have developed a niobium titanium nitride (NbTiN) based superconductor-insulator-superconductor (SIS) receiver to cover the 350 micron atmospheric window. This frequency band lies entirely above the energy gap of niobium (700 GHz), a commonly used SIS superconductor. The instrument uses an open structure twin-slot SIS mixer that consists of two Nb/AlN/NbTiN tunnel junctions, NbTiN thin-film microstrip tuning elements, and a NbTiN ground plane. The optical configuration is very similar to the 850 GHz waveguide receiver that was installed at the Caltech Submillimeter Observatory (CSO) in 1997. To minimize front-end loss, we employed reflecting optics and a cooled beamsplitter at 4 K. The instrument has an uncorrected receiver noise temperature of 205K DSB at 800 GHz and 410K DSB at 900 GHz. The degradation in receiver sensitivity with frequency is primarily due to an increase in the mixer conversion loss, which is attributed to the mismatch between the SIS junction and the twin-slot antenna impedance. The overall system performance has been confirmed through its use at the telescope to detect a wealth of new spectroscopic lines.     

Production of an Intense, Well-Collimated Submillimeter Wave Beam and Its Application to Plasma Scattering Measurements

Intense submillimeter wavelength radiation (f=354 GHz, P=110 W) from Gyrotron FU II is converted into a well-collimated, linearly-polarized beam by a quasi-optical transmission line consisting of a quasi-optical antenna and several mirrors. The observed focusing of the beam agrees with calculations based on the Huygens equation. We have used this intense beam to study low frequency density fluctuations by plasma scattering in Compact Helical System (CHS) plasmas at the National Institute for Fusion Science.     

一种新型低噪声大动态范围小型前端电路的研制

设计了一款小型化、低噪声、大动态范围的前端处理电路,包括电荷灵敏前放、成形放大电路、单道脉冲幅度分析电路。前放的等效输入噪声≤1.5 keV,动态范围可达0~11 V,积分非线性 ≤0.11%。该电路为模块化电路,当前放与主放模块构成系统时,其分辨可以达到0.12%。当前放、主放模块与中国科学院近代物理研究所制作的离子注入型硅探测器构成系统时,采用239Pu 源进行测试,测得在5.157 MeV时的能量分辨约为0.82%;当主放、单道脉冲幅度分析模块与中国科学院近代物理研究所制作的碘化铯晶体探测器构成系统时,采用60Co 源进行测试,对于能量为1.332 MeV 的 射线,测得其能量分辨约为7.9%。该电路可用于半导体探测器、光电倍增管及电子倍增器等探测器信号的处理。目前,小型前端电路已经应用于中国科学院近代物理研究所自行研制的便携式盐湖卤水铀、钍、钾快速测量仪的原型样机,达到了预期效果。A small dimension front-end circuit with low noise and wide output dynamic range is introduced in this paper. The front-end circuit is made up of a charge sensitive preamplifier, a shaping circuit and a single channel pulse height analyzer. The equivalent input noise is under 1.5 keV. The output integral nonlinearity is less than 0.11% within the dynamic range of 011 V. And the circuit can be suitable for different conditions by different modules. The resolution was about 0.12% with the charge sensitive preamplifier and the main amplifier. The energy resolution of 0.82% was achieved for 5.157 MeV -rays from a 239Pu source with the charge sensitive preamplifier, the main amplifier and anion-injection silicon detector designed by the Institute of Modern Physics(IMP). An energy resolution of 7.9% was achieved for 1.332 MeV rays from a stationary 60Co source with the main amplifier, the single channel pulse height analyzer and a CsI scintillator detector designed by the IMP. The front-end circuit has the features of wide output dynamic range, simple structure, high level of integration,small dimensions, low noise, fast rise time of the output pulse and excellent stability. The front-end circuit can be applied to signal processing of semiconductor detectors, photomultiplier tubes and electrons multiplier. And the front-end circuit had been applied to a prototype of the portable rapid measuring instrument designed by IMP for measuring Uranium, Thorium and Potassium in the salt lake brine with goodtest result.     

低噪声不隔直光电探测电路的设计

光电探测电路是光纤通信和光电检测系统中光信号转换成电信号的关键部分,但现有光电探测器大都不能同时测量脉冲光信号与直流光信号。为了获得低噪声并且能够同时测量脉冲光信号和直流光信号的光电探测器,设计一个不隔直光电探测电路,采用平衡放大方式消除直流工作点不稳定问题,提出了一种利用谐波分析法测量光电探测电路带宽的方法;同时对影响噪声的各种因素进行了研究,计算了探测电路的噪声电压和电流,提出了利用降低温度的方法提高信噪比。结果表明了该方法的有效性。     

低噪声不隔直光电探测电路的设计

光电探测电路是光纤通信和光电检测系统中光信号转换成电信号的关键部分,但现有光电探测器大都不能同时测量脉冲光信号与直流光信号。为了获得低噪声并且能够同时测量脉冲光信号和直流光信号的光电探测器,设计一个不隔直光电探测电路,采用平衡放大方式消除直流工作点不稳定问题,提出了一种利用谐波分析法测量光电探测电路带宽的方法;同时对影响噪声的各种因素进行了研究,计算了探测电路的噪声电压和电流,提出了利用降低温度的方法提高信噪比。结果表明了该方法的有效性。     

The Development and Application of Low Temperature Plasma Technology

The development and applications of low temperature plasma technology used in surface modification of materials are presented in this paper. Based on plasma sources and ion sources technology, multi-functions ion implantation and deposition technologies were developed and the related processes are also used to treat different products. The related technologies were translated into industrial productions supported by national research projects. Following the last development of international plasma researches, the standardization and internationalization processes of plasma technologies are executed in our center.     

Low frequency impact sound transmission in dwellings through homogeneous concrete floors and floating floors

An experimentally validated analytical model has been developed in order to investigate the effect on impact sound transmission at low frequencies of location of the impact, type of floor, edge conditions, floor and room dimensions, position of the receiver and room absorption. The model was developed in order to allow rapid repeated calculations necessary for a parametric survey, described in a companion paper. The analytical model uses natural mode analysis to predict the sound field generated in rectangular rooms by point sound sources and the point excitation of homogeneous rectangular plates with different edge conditions. A floor-room model of the sound field generated in a room by a vibrating floor also has been derived. Laboratory and in situ measurements confirm that the models can be used to estimate impact sound transmission at low frequencies. The approach applies to homogeneous simply supported base plates of uniform thickness with homogenous floating floors, which again were experimentally validated in the laboratory and in situ.     

温度/应变/扭曲三参量同时测量低成本传感系统

提出了一种利用布喇格光纤光栅反射光作信号源、高频CO2激光脉冲写入的长周期光纤光栅和超周期光纤光栅作传感器实现温度、应变和扭曲同时测量的全光栅型低成本强度解调传感方案.文中利用长周期光纤光栅边缘滤波效应实现了温度、应变和扭曲传感信号的实时解调.实验结果表明,其温度和应变的测量灵敏度分别为－0.211 dB/℃和－0.012 dB/10με;而扭曲率的测量灵敏度为0.4394 dB/(rad·m－1),是该法写入普通LPFG的4倍以上.     

Low temperature probe for dynamic nuclear polarization and multiple-pulse solid-state NMR

Here, we describe the design and performance characteristics of a low temperature probe for dynamic nuclear polarization (DNP) experiments, which is compatible with demanding multiple-pulse experiments. The competing goals of a high-Q microwave cavity to achieve large DNP enhancements and a high efficiency NMR circuit for multiple-pulse control lead to inevitable engineering tradeoffs. We have designed two probes-one with a single-resonance RF circuit and a horn-mirror cavity configuration for the microwaves and a second with a double-resonance RF circuit and a double-horn cavity configuration. The advantage of the design is that the sample is in vacuum, the RF circuits are locally tuned, and the microwave resonator has a large internal volume that is compatible with the use of RF and gradient coils.     

天文像复原迭代位移叠加法中的噪声偏差补偿

当工作于实际数据时，由于存在着多种噪声，导致了天文像复原迭代位移叠加法中的噪声偏差项，为消除这些噪声偏差项的影响，分别讨论了在观测目标和参考星的斑点数据期间由大气视宁度差异引入的系统误差和探测器严重的附加噪声产生的偏差，并给出了对这些噪声偏差项的补偿方法。     

Low sintering temperature MnZn-ferrites for power applications in the frequency region of 400 kHz

In this paper, the effect of cubic zinc metaborate Zn₄O(BO₂)₆ on the sintering of MnZn-ferrites for medium frequency power applications is investigated. Zinc metaborate is synthesized in the laboratory using zinc oxide and boric acid as metal precursors. As observed, when zinc metaborate is added to the MnZn-ferrites at an optimum amount of 0.02 wt%, it significantly enhances densification and therefore allows, for a given density, reduction of the firing temperature by almost 200 °C. MnZn-ferrites exhibiting power losses of 70 mW/cm³ (measured at a frequency of 400 kHz, magnetic field 50 mT and temperature of 90 °C) are synthesized from conventionally milled powders with average particle diameter 0.6 μm, compacted and fired at 1100 °C. Identical experiments conducted under the same conditions on specimens without zinc metaborate additions revealed power losses greater than 300 mW/cm³, because of insufficient densification.     

低温氢化物原子荧光法砷的氢化反应和原子化

以空心阴极灯作激发光源,选择了低温氢化物原子荧光法测定砷的最佳工作参数。采用双氢化发生法,研究了砷的氢化反应机理和原子化机理。     

光纤稳相微波频率传输中相干瑞利噪声的影响与抑制

利用光纤进行相位稳定的微波频率参考的远距离分配,在深空科学研究、基础物理测量以及多基地雷达技术方面有着广泛的应用需求。研究了基于往返相位校正的光纤稳相传输理论,建立了稳相传输的理论模型,搭建了基于光电延迟锁相环的光纤稳相传输实验系统,理论分析并实验研究了相干瑞利散射噪声对系统传输相位稳定性的影响。研究发现相干瑞利散射噪声不仅直接造成远端信号信噪比恶化,并且通过锁相环路转化为系统残余相位噪声,进一步恶化远端信号的稳定性,成为影响稳相传输系统性能的主要因素。针对该问题,提出了双波长的稳相传输技术,有效地克服了相干瑞利散射噪声的影响,实现了10GHz微波频率参考、100km光纤稳相分发,传输至远端的相位均方根抖动(RMS-jitter)低于730fs。     

测量托卡马克可见光谱辐射的低噪声,高响应光敏二极管探测器

研制了一种用于托卡马克等离子体可见光谱线测量的半导体光敏二极管探测器，这种探测器具有体积小，造价低，使用方便等优点，它具有很高的量子效率，理想的线性区，宽的频率范围和低的噪声，完全能够满足托卡马克诊断中对等离子体可见微弱谱线的测量。     

Temperature Effects on Attenuation Due to Rain for Millimeter and Centimeter Waves

Radio wave operating in millimetrewave and microwave frequency bands are adversely affected due to rain. Particularly the attenuation is of immense significance for sensitive remote measurements by satellites using frequencies greater than 10 GHz. Maintenance of an uninterrupted communication link requires a precise knowledge of the attenuation effect due to rain for commissioning right kind of transmitting sources for various purposes required in present day situation. Precise measurement of attenuation at various frequencies will enable us to choose the right frequency, polarization, incident angle and power of the source for different purposes. In this paper we have compared the results of earlier works using aR^b Olsen et al, (1) and the formulation by Moupfouma, (2) on the basis of theoretical analysis for explaining the observed results. Effect of temperature, considered in detail in this communication, has contributed the necessary correction factor of the rain attenuation for explaining the observed results. Theoretical analyses to measure the attenuation of the propagating wave due to temperature variation in the rain path have been presented. Correction factor due to temperature profile (temperature from the ground to the rain height within which the radio wave traces its path) has been incorporated in two models by using the concept of dipole energy changes. The effect of this temperature is noted to be quite significant and incorporates an error to the extent of 7–8%.     

Technique of Broadband Measurements of Frequency Conversion Efficiency for Each Harmonique in Frequency Multipliers up to Terahertz Range

The paper describes technique of quantitative analysis of a millimeter- and submillimeter-wave range multipliers performance in particular the measurement of the frequency conversion efficiency. The output power on each harmonic produced by the multiplier can be measured separately without any changes in the setup even in the case of simultaneous emission of all harmonics including the fundamental in a frequency range up to 1 THz and well above. The measuring technique primarily developed for high resolution microwave spectroscopy is based on absorption of radiation in spectral lines of rarefied sample gas and photo-acoustic method of the absorption detection. Sensitivity independence of the detection method on frequency and well known spectral parameters of the lines provide the technique with broadbandness, high spectral resolution and power measurement reliability. Principal limits of measurable radiation power may vary from nanowatts up to hundreds of watts. The technique permits real time operation convenient, e.g., for multiplier tuning. Practical examples include measurements of harmonic generation efficiency of multipliers of 78-118 GHz fundamental frequency range, and power measurement up to 6-th harmonic of 230 GHz fundamental radiation of phase locked Backward Wave Oscillator (BWO).     

Effecfs of Cross-Correlation Between Real Noise in Transient Process of Single-Mode and Imaginary Parts of Colored Pump Laser

A two-dimensional single-mode laser model with cross-correlation between the real and imaginary parts of the colored quadric pump noise is investigated. A novel laser amplitude Langevin equation is obtained, in which the cross-correlation λp between the real and imaginary parts of the pump noise appears. The mean, variance, and skewness of first-passage-time are calculated. It is shown that the mean, variance, and skewness of first-passage-time are strongly affected by λp.     

Low temperature high-pressure crystallization and fluid phase equilibria in the systems Ar + CHF3 and N2 + CHF3

Abstract

An optical autoclave for phase studies on mixtures in the temperature range from 80 to 373 K and for pressures up to 200 MPa is described. The cell is fitted with sapphire windows and employs magnetic stirring. Measurements are performed according to the synthetical (e.g. by visual observation) or analytical method (e.g. by sampling and online gaschromatography). Results for the crystallization and fluid phase equilibria of the binary systems nitrogen + trifluoromethane and argon + trifluoromethane from 110 K to 230 K and up to 200 MPa are presented and discussed in comparison with other N₂- and CHF₃-systems.