基于载波相移系统的二倍频光电振荡器

为了扩展光电振荡器(OEO)的频率范围,设计了 一种基于载波相移系统的二倍频OEO(FD-OEO)。 系统采用相位调制器(PM)和Mach-Zehnder调制器(MZM)并联,构成载波相移系统,利用载 波相移双边带(CPS-DSB) 调制的方法产生二次谐波分量;同时利用啁啾光纤布拉格光栅(CFBG)色散特性实现边带分 量与CPS补偿,维持 OEO环路中基频信号的振荡。实验结果显示,在OEO环路系统基频信号为2.23GHz情况下,产生了4.30 GHz的FD信号,且通过边模抑制性能、稳定性及相位噪声对系统性能进行了验证。     

加速度地震检波器简谐振子有限元分析

介绍简谐振子的工作原理。利用ANSYS软件,采用有限元法创建了简谐振子质量块的实体模型,选择单晶硅作为简谐振子中质量块的材料;设置了模型的材料属性,采用智能分网的方式对模型划分网格,并对质量块模型施加沿x轴水平方向载荷,进行三维的静力分析和模态分析。静力分析得到实体模型的总位移是0.236×10-19μm;模态分析时只对前四阶模型进行了分析,根据其振型图及其总位移的应力云图,得到实体模型的二十阶振动模态的频率是78 001Hz,二十阶的总位移是0.122×10-6μm。     

A 5-GHz LC VCO with digital AAC and AFBS for 2.4 GHz ZigBee transceiver applications

A 5 GHz LC VCO (voltage-controlled oscillator) with automatic amplitude control (AAC) and automatic frequency-band selection (AFBS) for 2.4 GHz ZigBee transceivers is presented. Instead of continuous feedback loop, an alternative amplitude calibration scheme is proposed in this paper to alleviate the deficiencies inherent in the conventional approach. It helps to keep the VCO at optimum amplitude to avoid saturation of the cross-coupled transistors and therefore stabilizes the phase noise performance over process, voltage and temperature variations. For the ZigBee application with 16 frequency channels, a coarse tuning loop is added in this work to implement the frequency-band selection using the AFBS mechanism. The VCO core and the digital AAC, AFBS modules have been fully integrated in a 2.4 GHz ZigBee transceiver which was fabricated in a 0.18 μm RF-CMOS technology. The current consumption is 4.7 mA at 4.85 GHz with 1.8 V power supply and a chip area of about 0.285 mm² is occupied. The VCO is capable of operating from 4.67 GHz to 5.18 GHz and the measured phase-noise level is –120 dBc/Hz at 1 MHz offset from a 4.85 GHz carrier. The tuning sensitivity K_VCO of the VCO is about 78 MHz/V with 0.9 V control voltage.     

变参数法优化方坯连铸机结晶器振动参数

研究如何用变参数法优化结晶器振动装置的振动参数,使振动装置在满足工艺要求的条件下,稳定性和可靠性均能得到有效的提高。     

小方坯连铸机结晶器振动装置设计及特点

小方坯连铸机结晶器振动装置采用半板簧结构,双偏心驱动,内弧侧布置,设有弹簧过载保护装置,集合了仿弧精度高、结构简单、重量轻诸多优点。通过ADAMS机械系统动力学仿真分析软件创建振动系统虚拟样机模型,用其求解器对系统进行运动学分析,然后进行设计优化,获得高仿弧精度的结晶器振动装置的结构位置关系。最后对振动装置进行动态静力学分析,计算驱动力矩,为电机的选取和强度校核提供了依据。     

基于THz波的玻璃纤维复合材料无损检测方法研究

太赫兹具有透视性、安全性等特点,近年来在无损检测领域得到了较快的发展和应用,以返波振荡管连续太赫兹波成像系统对5mm厚的玻璃纤维复合材料进行无损检测实验,其中包括热损伤(dmin=0.5mm)、空气分层(smin=0.5mm2)等缺陷,获得样品的成像结果及数据。结果表明,返波振荡管连续太赫兹波成像技术对从背面对玻璃纤维复合材料样品中的两种缺陷有清晰成像,且结合成像数据,可排除样品中环氧树脂的影响,验证不同缺陷之间的特性,进一步确定损伤类型。     

Temporal coordination and adaptation to rate change in music performance.

People often coordinate their actions with sequences that exhibit temporal variability and unfold at multiple periodicities. We compared oscillator- and timekeeper-based accounts of temporal coordination by examining musicians' coordination of rhythmic musical sequences with a metronome that gradually changed rate at the end of a musical phrase (Experiment 1) or at the beginning of a phrase (Experiment 2). The rhythms contained events that occurred at the same periodic rate as the metronome and at half the period. Rate change consisted of a linear increase or decrease in intervals between metronome onsets. Musicians coordinated their performances better with a metronome that decreased than increased in tempo (as predicted by an oscillator model), at both beginnings and ends of musical phrases. Model performance was tested with an oscillator period or timekeeper interval set to the same period as the metronome (1:1 coordination) or half the metronome period (2:1 coordination). Only the oscillator model was able to predict musicians' coordination at both periods. These findings suggest that coordination is based on internal neural oscillations that entrain to external sequences. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

A measurement system for YTO

Yttrium iron garnet（YIG） tuned oscillator （YTO）,which is widely used in signal source,is difficult to be measured manually for its numerous parameters.In order to accomplish the measurement of YTO quickly and automatically,this paper gives the design of an auto-measurement system based on genernal purpose interface bus （GPIB）.     

Design of a PLL with improved locking range and its biomedical applications

This paper describes a phase locked loop employing a low voltage VCO using modified ECL inverter cells. The VCO circuit employed, features a positive feed back scheme to improve the operating frequency. The phase detector used in the PLL also uses a positive feedback scheme to improve the locked range and to reduce supply voltage of operation of the entire circuit. An improvement of locked range of around 35% was obtained from circuit simulation (using PSPICE) as well as from practical circuit, using discrete components. The minimum supply voltage required here is 2.5 volts. Some biomedical applications of this PLL are also proposed.     

Highly sensitive ultraviolet detector using a ZnO/Si layered SAW oscillator

This study elucidates a highly sensitive ultraviolet light detector using the combination of an oscillator circuit with a high-frequency amplifier, a matching network and a layered surface acoustic wave (SAW) device. In this structure, a ZnO thin film is simultaneously used as an active layer for UV detection and a piezoelectric layer for exciting a high-order surface acoustic wave. The microstructure and crystallization of ZnO films were investigated using the scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. The SAW oscillator shows a good performance with output power of − 1.14 dBm and phase noise of −94.7 dBc at 100 kHz. Firstly, the frequency shifts of the oscillator exhibit rapid increase with the intensity of the UV light. Then the increased shifts decayed at certain UV intensity due to the saturated photogenerated carriers. An extreme frequency shift of 1017 kHz was obtained as the UV intensity reached 551 μW/cm². The maximum sensitivity of 8.12 ppm/(μW/cm²) can be obtained in this detector.