抑制谐波可变增益混频器的设计

基于0.5μm SiGe HBT工艺,利用安捷伦公司的ADS仿真软件,设计一款应用于GNSS接收机射频前端的Gilbert混频器芯片。设计的混频器将开关管级差分对管的输出端用连接线接到片外电感,与片内的电容组成带通滤波器作为混频器的负载,实现增益的可调,并获得较高的谐波抑制能力和较低的功耗(18mW),输出中频频谱很好。混频器的NF为4.6dB,增益为10dB。     

用于精确位置控制的谐波传动控制精度研究

建立精密谐波传动数学模型,分别研究线性控制器和脉冲控制器的精度,继而定量讨论摩擦力对脉冲控制器的精度影响。仿真和试验结果表明:谐波传动的摩擦力会严重降低脉冲控制器的性能;脉冲控制器的准确度高于线性控制器的准确度。该研究将有益于谐波传动在高精密控制系统中的应用。     

X波段高功率微波脉冲鉴相器设计与实现

为满足高功率微波技术对信号相位差测量的应用需求,设计一种微波脉冲鉴相器,实现X波段脉冲信号相位差的准确测量。鉴相器基于I/Q解调原理,采用无需外加电源供电的双平衡电路结构,以微带电路的形式设计同相功分器和分支线电桥,结合贴片式混频器将两路待测信号进行正交混频,得到与待测相位差相关的电脉冲。电路设计中采用宽带电路结构,扩展使用带宽;结合全电磁仿真对各信号传输通路的相位一致性进行分析计算,避免电路出现初相误差;采用低通滤波器滤除高次谐波干扰,提高鉴相准确度,最后制作实物样机并进行性能测试。测试结果表明,该鉴相器能够实现百纳秒级微波脉冲信号的相位测量,动态范围达到10 d B,最大承受功率22 d Bm,测量误差5°。     

有理数谐波锁模SOA光纤环形激光器数值研究

采用自再现理论,对工作在有理数谐波锁模时的半导体光放大器(SOA)光纤环形激光器进行了研究.为了获得振幅均衡的有理数谐波锁模脉冲,必须在原有的实验装置中添加一个掺铒光纤放大器(EDFA)以提高注入调制光信号功率.数值结果表明,调制SOA的偏置电流和注入调制光信号功率对有理数谐波锁模脉冲的振幅均衡度都存在较大影响.合理选择调制SOA的偏置电流和注入调制光信号功率,可获得2～5阶振幅均衡的有理数谐波锁模脉冲序列.     

谐波对电子积分器测量磁通的影响分析研究

研究了谐波对电子积分器测量磁通的影响,通过matlab中的simunlink建立积分器的数学模型,仿真积分器对伏秒脉冲周期信号的响应.理论分析理想积分器的低通滤波性同时分析伏秒脉冲信号谐波对近似积分器的影响.实验表明伏秒信号的谐波成分越大,对积分器测量越不准确.     

基于D类功放的声呐发射机驱动信号分析

针对声呐发射机对功放电路提出的大输出功率、输出功率可调以及谐波能量小的需求,提出了一种改良的脉冲宽度调制方法.该方法选用中心宽脉冲,两边对称分布两个窄脉冲的半周期三脉冲信号形式,得到了宽窄脉冲间的比例关系,最后通过计算找到了最优的脉冲间距.MATLAB仿真以及水池声呐实验表明,该方法在基波能量的整个变化过程中,3次与5次谐波能量最大不超过基波能量最大处的2%.     

一种用分谐波讯问技术实现的微波无触点辨别式异频雷达收发机

本文介绍了一种新式微波异频雷达收发机的设计和分析.该收发机在分谐波推拉式准光学混频器的基础上,由C波段讯问光束激活,转换成两个X波段频率的数字型调制辨别光信号,该响应信号与讯问信号非分谐波相关.通过运用包括考虑自偏电流影响的Volterra级数模式和在无线电连接计算中直接有效的散射米制方法对频率变换过程进行分析.该收发机能够遥控识别人员和物品.     

纳米射频CMOS混频器的研究

介绍了混频器的工作原理、性能指标及几种重要的混频器结构。设计了以Gilbert型为核心的双端差分对混频器，使用TSMC的0．18μm CMOS工艺库，本振信号为2．25GHz，射频信号为2．5GHz；借用安捷伦公司的ADS软件模拟，模拟结果变频增益为-10dBm，双边带噪声为58．6dB，输入1dB压缩点为11dBm，同时端口隔离度也比较高。该混频器适用于中高频段的发射机。     

脉冲反转技术在金属疲劳损伤非线性超声检测中的应用

材料性能退化总是伴随着某种形式的材料非线性力学行为,从而引起超声波传播的非线性,即高频谐波的产生。研究了利用脉冲反转技术测量金属材料超声学非线性系数的实验方法和信号处理算法,发展了一套可靠的测试实验系统,在相同条件下测量了同一试样在不同输入电压下的二次谐波和基波幅度,二次谐波幅度和基波幅度的平方近似成线性关系,表明实验系统是可靠的。利用该系统进行了一组LY12铝合金疲劳试样非线性超声检测实验。实验结果表明,超声非线性系数可以表征镁合金的疲劳早期退化,脉冲反转技术能够有效提取二次谐波时域信号,增强二次谐波的幅度,抑制主要由实验系统所产生的奇次谐波分量,为材料和结构早期力学性能退化的无损检测和评价提供一种有效的方法。     

我国精密电磁测量成果世界瞩目

在一年一度的国际精密电磁测量会议《CPEM’96)上,我国发表的学术论文普遍受到各国专家的关注。这标志着我国精密电磁测量技术达到了国际领先水平。不久前,在德国布伦瑞克召开的国际精密电磁测量会议和国际科学数据委员会基本物理常数任务组会议上,46个国家的596名代表参加了这次规模最大、水平最高的国际学术交流会。会议期间还展示了直流、微波、时间频率、光频测量、基本物理常数测量等领域的科技最新成果。我国在会议上发表了5篇学术论文,中国计量科学研究院与南京大学合作的《高温超导谐波混频器在我国约瑟夫森结阵电压基准中的应用》论文,受到各国同行的重视。这是因为约瑟夫森结阵电压基准中采用高温超导结比常温二极管混频效率大大提高,所以引起了我国专家的重视。经过讨论与交流,一些外国公司准备在我国研究的基础上合作开发新产品,有的提出利用高温超导谐波混频器开发100GHZ锁相微波源产     

Millimeter Wave Harmonic Mixing with Hot Carrier Diodes

The harmonic mixing performance due to hot carrier diodes utilizing high field effects in semiconductors has been investigated. Model experiments in the 35-GHz band have been performed to obtain the optimum structure and NEP (Noise Equivalent Power). NEP of 2 × 10-11 W/5-MHz for a 3rd-order harmonic mixer was obtained.     

New vector signal measuring system, featuring wide bandwidth, large dynamic range and high accuracy

A new measurement system, with two receiver channels per measurement port, has been developed that provides absolute magnitude and absolute phase relationship measurements over wide bandwidths. Gain ranging is used at radio frequency to provide optimum noise performance and a swept yttrium iron garnet (YIG) preselector filter is used to avoid spurious signals. A new absolute vector error correction method is used to calibrate the measurement system in order to allow for absolute vector measurements, and it also removes the time-varying responses caused by the swept YIG preselector filters. A quasi-reciprocal mixer with a characterised non-reciprocal ratio is used to provide the absolute calibration standard. The two receiver channels can be adapted to a wide variety of applications, including wide bandwidth vector signal analyser measurements, mixer measurements and harmonic measurements. The two channels can also be used as an absolute calibrated transmitter/reflectometer.     

Flow of two-phase mixtures in a rotary mixer

On the basis of a hydrodynamic model of a multivelocity continuum, the flow of miscible materials over the working surface of a multistage centrifugal (rotary) mixer is investigated, and the optimal dimensions of the working sections required to obtain a high-quality mixture are determined.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 32, No. 2, pp. 226–233, February, 1977.     

Improvement of the FMCW laser range-finder by an APD working as an optoelectronic mixer

A laser range-finder has been designed for distances from 1 to 20 m with diffusing targets. The measurement principle using a frequency modulation continuous wave technique is first described. Improvement for short distance measurements is then proposed with a new set-up using a delay line and an avalanche photodiode working as an optoelectronic mixer used to obtain a wide-band and a low-noise photoreception.     

谐波减速器在空间飞行器中的应用

首先介绍了谐波减速器的传动原理和特性,然后介绍了美国、欧盟、日本等国家和地区发展、应用空间谐波减速器的概况,分析了谐波减速器应用于空间环境的关键技术,最后提出了我国开展星用谐波减速器研究的建议.     

Two-dimensional weak-object transfer functions in the scanning harmonic microscope

Abstract

The two-dimensional imaging properties of scanning harmonic microscopes are considered. The two-dimensional weak-object transfer functions for non-confocal (point source and large-area incoherent detector) and confocal (point source and point detector) scanning harmonic microscopes are calculated. Results show that the harmonic microscopes are capable of super-resolution in that the spatial frequency cut-off is twice that for a microscope working at the fundamental wavelength. Confocal scanning harmonic microscopes exhibit better resolution than the conventional type.     

基于ADAMS谐波减速器的模态分析

为了研究谐波减速器在工作过程中的振动情况,避免共振,首先根据计算得到的主要零部件参数,在Pro/E中建立谐波减速器的刚体三维模型;然后利用ANSYS对谐波减速器的柔轮进行模态分析;最后在ADAMS中建立谐波减速器刚-柔混合虚拟样机,并进行整机模态分析.分析得知,该谐波减速器设计合理,不会产生共振现象,具有良好的动力学性能.     

Pulsed 5-GW resonance relativistic BWT for a decimeter wavelength range

The results of numerical modeling and experimental investigation of a high-power, resonance relativistic backward wave tube are presented. By using the working TM₀₁ mode reflections from the ends of the electrodynamic system, optimum conditions for the electron beam interaction with both the (−1)st harmonic of the backward electromagnetic wave and the main harmonic of the concurrent wave are achieved. A single mode generation with 5 GW output power and a 30% efficiency was obtained in experiments at a frequency of 3.6 GHz. The working frequency can be controlled within 15% (at the half maximum power level) by changing the slow-wave structure period at the constant electron beam parameters.     

生产MHY-4黑火药的三料球磨机的设计及应用

用铸铝球磨机生产MHY-4黑火药,设备使用寿命长,散热性好,可以降低黑火药生产过程中的静电积累,提高黑火药生产的安全系数.