无线激光通信音频传输实验

设计了无线激光通信音频传输实验系统.在发射端采用对90 MHz载波信号调频方式调制放大信号后,再对半导体激光器进行强度调制;在接收端光信号由光电探测器转换为电信号,电信号经中频放大器、变频器和鉴频器解调出原始信号,原始信号再经功率放大器放大后由示波器接收.测量了实验系统音频传输的幅频特性、动态特性和延迟特性.实验结果表明:由于采用二次调制,系统抗干扰能力强,接收灵敏.     

热释电红外传感器在无线遥控报警系统中的应用

热释电红外探测无线遥控报警系统由热释电红外探测模块、无线电收/发射模块、数字编/译码集成电路和语音录放模块组成。当人体进入监视区时,红外传感器首先将接收到的红外辐射能转换成电能信号,再经内部电路放大处理,输出控制信号启动发射系统工作,经编码脉冲调制后, 由发射模块向空间辐射无线电遥控编码信号;接收机收到信号后,便进行解调、放大、整形,从解码器输出编码脉冲,然后触发语音录放系统,播放事先录制好的警示语,提醒值班人员。该系统主要采用了RDP-18热释电红外探测模块,具有从信号接收至控制输出的全部功能。整体装置为模块化结构,具有频率稳定、工作可靠、免调试等特点,遥控距离1 000 m,可适用于多种场合的需要。     

一种基于单片机无线收发系统设计

设计一种基于STC89C51单片机的无线收发系统,本设计采用频率合成技术、FM调制技术及超外差解调技术,单片机对锁相环本振频率(发射43MHZ、接收53.7MHZ)锁定并通过液晶显示,本振频率在一定的范围内可调。将音频信号、咪头信号和数字英文字母信号作为调制信号,最后实现了音频、数字、英文字母等信号的重现。     

热释电红外探测器在安全防护系统中的应用研究

利用人体发出的红外线,通过热释电红外传感器的接收和放大,形成具有一定电压幅度的控制信号,用这一控制信号去触发语音录放电路工作,就可制成具有自动控制功能的热释电红外探测语音录放系统。电路采用最新热释电红外探测模块与语音录放模块设计,当有人出现在热释电红外探测模块的探测范围时,热释电红外传感器首先将接收到的红外辐射能转换成电能信号,再经内部电路放大、比较处理后输出控制信号,触发语音录放模块工作,播放事先录制好的语音内容,提醒人们注意。该系统电路简洁、成本低、抗干扰能力强、耐低温、免调试、工作稳定和使用方便。适宜于安装在变电所、高压开关柜和电力变压器等危及人身安全的处所使用。     

基于摄像头的MIMO可见光无线通信系统

给出了一种涉及多光源的多输入多输出(MIMO)可见光无线通信(VLC)系统。通过编程模拟出n个发射光源,分别发射n路不同的码流。无线信号接收端用摄像头来采集无线信号,对采集到的信号使用图像处理技术来识别各个传输通道的信息,并进一步恢复出n路码流。实验结果表明,实验中出现的少量误码均可被正确纠正,发送端发送的信号码流在接收端均可被正确地恢复出来。提出的系统通过更改信号接收机制,规避了基于光电二极管接收信号的现有系统中所存在的光源布局与同步难题及多径干扰问题。提出的多通道信号传输与接收方式,提高了光源利用率,因其可操作性而具有实用价值。     

移动式多基线能见度测试系统及其测量方法

针对单基线能见度测量设备采样体积单一、受噪声影响大的缺点,设计搭建了一套移动式可变基线能见度测试系统.该系统由发射、接收、移动以及信号处理四个模块组成,以532nm激光作为发射光源,通过置于滑动轨道上的小车移动定点接收发射信号实现多基线测量,然后采用时间平均结合最小二乘法对初始信号进行处理获得最终大气能见度.系统采用单端移动接收采样法,可从理论上消除光学污染误差.理论分析了该设备的测量方差及基线采样点模型,并对系统进行加噪声模拟实验,证明了其抗噪声能力;最后在真实大气环境下对设备进行检验,通过与实际数据对比证明其可靠性.     

激光羽烟透过率测试技术研究

为了准确评估固体推进剂的性能,研制了红外激光羽烟透过率测量系统。系统采用透射的方法:在发射端对激光信号采用内调制,由光学系统送入接收端,并将接收到的信号进行光电转换、信号处理和A/D转换后送入计算进行数据的处理和显示。现场测试结果表明该系统的精度、响应速度和稳定度达到设计要求。     

HDMP 1022/1024在高速光纤数据传输中的应用

介绍了Agilent公司的G-link芯片HDMP 1022(T_X)/1024(R_X)的结构和工作原理以及2种芯片和PECL逻辑电平输入/输出光发射模块/接收模块的接口电路。给出了用上述芯片组合构成点对点双向全双工光纤数据传输系统及单向传输系统的具体电路。叙述了这2种典型系统的启动和同步过程。该系统可用于高分辨率数字电视信号和其他高速数据信号的光纤传输系统。     

实时主动声定位系统设计*

针对在军事演习或爆炸实验中对冲击波超压传感器位置的精确定位,设计了一种实时主动声定位系统。该系统由声信号发射系统、声信号接收处理系统和无线监控终端系统三部分组成。声信号发射系统与无线监控终端以单片机STC12C5A60S2作为核心控制器,接收处理系统以ARM9系列的S3C2440作为核心控制器。发射系统发射四种已知频率的声信号,接收处理系统接收并处理收到的四种声信号,然后把处理结果反馈到无线监控终端。通过实验表明,该系统在一定条件下,能够稳定地发射、接收并处理声信号,达到实时定位目标,并在200 m范围内将定位误差控制在厘米级内。     

一种X射线聚焦光学及其在X射线通信中的应用

基于栅控脉冲发射X射线源与单光子探测技术的X射线通信已经实现了实验室语音通信验证,并对通信系统的误码率性能进行了分析,为探索未来X射线深空应用打下了坚实的基础.针对目前X射线通信面临的信号发散角大、通信距离短、难以实现工程化应用的情况,迫切需要对X射线通信天线系统进行深入研究.为了提高信号增益、增大X射线通信的距离,提出了多层嵌套式X射线聚焦光学作为X射线通信的"收发天线",理论分析了X射线聚焦光学用于X射线通信"收发天线"的可行性,分析了X射线聚焦光学的理论基础与结构设计,对"发射天线"发散角、"接收天线"有效面积与焦斑尺寸、信号增益等性能做了探讨.结果表明:在信号发射端,"天线"的发散角为3 mrad左右,发射增益23 d B;在信号接收端,"接收天线"的有效面积5700 mm2@1.5 keV,焦斑直径为4.5 mm,接收增益为25 d B,通信系统总的增益可达48 d B.     

Self-organization of five species in a cyclic competition game

Cyclic competition game models, particularly the “rock–paper–scissors” model, play important roles in exploring the problem of multi-species coexistence in spatially ecological systems. We propose an extended “rock–paper–scissors” game to model cyclic interactions among five species, and find that two of the five can coexistent when biodiversity disappears, which is different from the “rock–paper–scissors” game. As the number of fingers is five, we named the new model the “fingers” game, where the thumb, forefinger, middle finger, ring finger, and little finger cyclically dominate their subsequent species and are dominated by their former species. We investigate the “fingers” model in two ways: direct simulations and nonlinear partial differential equations. An important finding is that the number of species in a cyclic competition game has an influence on the emergence of biodiversity. To be specific, the “rock–paper–scissors” model is in favor of maintaining biodiversity in comparison with the “fingers” model when the variables (population size, reproduction rate, selection rate, and migration rate) are the same. It is also shown that the mobility and reproduction rate can promote or jeopardize biodiversity.     

Contrastive analysis on tone between Putonghua and Taiwan Mandarin

The differences of the pitch and duration of Chinese syllables between Putonghua （PTH） and Taiwan Mandarin （TM） were studied. The speech materials to be used are not only isolated syllables, but also sentences. The results reveal that： For the isolated syllables, T1 and T2 in TM are influenced by Minnan dialect, therefore their pitch are lower than those in PTH. T3 is fall-rise in PTH, while it is fall in TM. Moreover, the syllable duration sequence for different tone is T3〉T2〉T1〉T4 in PTH, while it is T1〉T2〉T3〉T4 in TM. For the syllables in sentences, T2 is mid-rise in PTH, while it is mid-level in TM. And the T3 is longer than T4 but shorter than T1 or T2 in PTH, while it is the shortest in TM. Furthermore the effects of prosodic phrase boundary on duration for different tones are almost the same in PTH, but the lengthening part of T1 or T2 is longer than that of T3 or T4 in TM.     

Experimental study on downstep in Chinese intonation

Downstep in pitch contour of Chinese Putonghua is examined using subtly designed sentences by controlling tone combinations. The results show both automatic and nonautomatic downstep phenomena exist in Chinese. In non-automatic downstep, low tones compress downwards the pitch range of the following syllables. and the main influence of downstep is on topline. Low tone not only lower the topline behind it, but also raise the high tones before it, the effects are compatible with each other. In automatic downstep, the topline of pitch contour in intonational phrase is presented as a linear downtrend, but it differs among speakers due to the effect of personal stress practice. In comparison with downstep phenomenon in other tone or non-tone languages, the downstep ratio in Chinese is not constant, and the domain of downstep is not limited within the adjacent tones.     

Abelian-Higgs phase of SU(2) QCD and glueball energy

It is shown that SU(2) QCD admits an dual Abelian-Higgs phase, with a Higgs vacuum of a type-Ⅱ superconductor. This is done by using a connection decomposition for the gluon field and the random-direction approximation. Using a bag picture with soft wall, we presented a calculational procedure for the glueball energy based on the recent proof for wall-vortices [Nucl. Phys. B 741(2006)1].     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Signal generation in an isotropic medium in scanning electron acoustic microscope

Based on the research in Ref. [5][Materials Science and Engineering, 1989; A122： 57 63], an improved model of heat source is set up, the different modes of Lamb wave in an isotropic sample generated by a chopped electron beam at frequency f are obtained with integral transform and normal function expansion method, and the output signal of PZT coupled at the back surface of the sample is found out. The generation mechanism of SEAM （Scanning Electron Acoustic Microscopy） signal is discussed. It shows that the SEAM is a near field imaging technique with high spatial resolution and its best lateral spatial resolution is about 2√2α （α is the radius of the focused electron beam）. Some of experimental results of SEAM images are presented in the paper and it shows that the spatial resolution of SEAM is better than 0.5 μm and smaller than the thermal diffusion length of the sample. Therefore the character of near field imaging in SEAM is also proved experimentally.     

High efficiency filtering using two-dimensional photonic crystal coupled cavity structures

Transmission spectra of coupled cavity structures (CCSs) in two-dimensional (2D) photonic crystals (PCs) are investigated using a coupled mode theory, and an optical filter based on CCS is proposed. The performance of the filter is investigated using finite-difference time-domain (FDTD) method, and the results show that within a very short coupling distance of about 3λ, where λ is the wavelength of signal in vacuum, the incident signals with different frequencies are separated into different channels with a contrast ratio of 20 dB. The advantages of this kind of filter are small size and easily tunable operation frequencies.