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无背景噪声下的光MPPM信道容量分析 总被引:3,自引:1,他引:2
基于多脉冲位置调制(MPPM)在无背景噪声下的信道模型,根据信息理论,推导了有保护时段的光MPPM信道容量的表达式,在此基础上又推出了MPPM的信息传输速率和容量能量效率的表达式.分析并比较了MPPM和PPM的信道容量、信息传输速率以及信道容量能量效率.仿真结果表明,在对光脉冲功率、系统带宽倒数、单个脉冲所含光子教等参数进行适当的选取以后,MPPM在信道容量方面的特性优于PPM. 相似文献
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Ti60合金在650~750℃高温下的氧化行为 总被引:5,自引:0,他引:5
研究了Ti60合金(Ti-5.6A1-4.8Sn-2.0Zr-1.0Mo-0.85Nd-0.34Si)在650~750℃下的高温氧化行为;采用恒温或循环氧化增重方法、氧化速度常数、活度等理论计算研究了合金氧化的热力学和动力学规律;用X射线衍射(XRD)、扫描电子显微镜(SEM)等方法,研究氧化膜的表面形貌和结构;采用俄歇电子能谱(AES)分析元素沿深度方向的分布,研究元素在氧化过程中的扩散行为。研究结果表明:Ti60合金在650℃和700℃有较好的抗氧化性能,其循环氧化动力学曲线基本上符合抛物线规律;在750℃,氧化严重,其循环氧化动力学曲线近似符合抛物线一直线规律。氧化层由金红石结构的TiO2氧化物和少量的Al2O3组成。氧化表面形貌为网篮状组织,这是由于α相和β相的成分和结构不同,界面扩散和体扩散差异导致的氧化程度不同所造成的。稀土第二相处氧化严重,表面裂纹大多产生于稀土第二相颗粒。 相似文献
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本文将矢量传感器应用于频率调制的水声通信系统中,利用声强解码代替传统的声压解码.借鉴QPSK信号星座图,发明了一种BFSK信号解调后的显示方法,该方法可直观的显示出信噪比系统带宽和误码情况.仿真研究结果表明,基于矢量传感器的通信系统利用声强解码可以扩大通信距离,降低误码率. 相似文献
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《中国测试》2013,(5):124-128
为提高跳频通信的抗干扰性能,设计一种新的短波跳频通信技术——图样调制跳频(pattern modulation frequency hopping,PMFH)系统。该系统将跳点分组,以载波发射的相对位置代表信息比特。通过增加调制域的冗余度和基带信号能量,以频带和功率资源换取信噪比,同时保护了跳频序列。为克服跳同步后静默时间对信号帧同步的影响,设计同步字检测方案和多图样匹配方案。结果证明:多图样匹配方案的性能较好,在信噪比大于0dB时,7位Gold图样的帧同步概率不小于80%,31位Gold图样的帧同步概率不小于95%,图样调制跳频技术使跳频通信在恶劣信道中的可靠性显著提高。 相似文献
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《中国新技术新产品》2016,(7)
斗轮堆取料机负责给全厂锅炉供煤,运行过程中经常会出现联锁保护异常,影响供煤效率。常规控制通信信号经常误发或拒发,通过改造为无线通信控制之后,很好的解决了通信问题,保证了联锁保护的正常,使整个供煤系统稳定有序地运行。 相似文献
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为了估计水下激光成像系统的工作距离,根据水下激光成像系统的成像过程,通过分析目标的辐射特性,水体的衰减特性等各因素,建立了水下激光成像系统的信噪比模型.根据识别目标所需要的信噪比阈值、脉冲激光器等器件的性能指标,推导出水下激光成像系统的工作距离公式,并且完成了系统成像距离的计算与仿真.采用532 nm的Nd∶YAG固体激光器、自组ICCD相机以及基于FPGA技术设计的同步控制电路板,进行了距离选通水下激光成像实验.实验结果表明:理论模型计算的信噪比与实际图像的信噪比平均误差为1.37 dB,证实了该模型的合理性. 相似文献
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基于模糊判别准则的马田系统基准空间优化 总被引:5,自引:0,他引:5
应用模糊数学及稳健性设计原理,从理论上证明了望大特性模糊稳健性判别准则能同时使均值达到最大和方差达到最小,其效果与望大特性信噪比稳健性判别准则一致.通过实例,分别使用两个判别准则对马田系统基准空间进行优化,得到了一致的最优方案. 相似文献
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1CDMA系统干扰摄述1.1干扰的概念CDMA系统与其他的移动通信系统共存于一个复杂的无线环境中,由于每种通信系统都会采用各种复用方式来提高频谱利用率,增加容量,势必会引入同频、邻频干扰,同时无线系统还存在着电波传播多径效应造成的干扰和某些无线射频设备产生的干扰等。1.2CDMA系统抗千扰性分析1)无线频谱利用率高,抗干扰性强:在CDMA扩频通信技术中,在发送端信号被扩展到很宽的频带上发送,在接收端扩频信号带宽被压缩,恢复成窄带信号。干扰信号与扩频伪随机码不相关,被扩展到很宽的频带上后,进入与有用信号同频带内的干扰功率大大降低,从而增加了输出信号/干扰比,因此具有很强的抗干扰能力。抗干扰能力与频带的扩展倍数成正比,频谱扩展得越宽,抗干扰的能力越强。 相似文献
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Abstract It is shown that the performance of optical communication systems that use pulse position modulation and direct photon counting can be improved with the use of squeezed states. The effect of noise is studied. An improved version of the pulse position modulation called extended position modulation is also considered. 相似文献
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为弥补当前位置跟踪系统控制精度不高和有线数据传输的不便,设计了一种高精度无线角位置跟随控制系统。采用多量程高精度L3G4200DH三轴陀螺仪作为角位置传感器,通过2.4G NRF24L01无线射频收发芯片实现数据传输,以ARM Cortex-M3作为微控制器,使用模糊PID全闭环控制算法对伺服电机进行控制,并且加超前校正和前馈环节,改善角度输入响应滞后,从而减小系统的跟随误差。同时采用无线视频模块实时监控伺服电机状态。通过仿真和实验证明,伺服系统在精度和实时性上有了很大提高,动态跟随精度达到了10-3,具有较好的跟随特性,同时无线数据传输方式将给远程控制和特殊作业环境带来极大的便捷。 相似文献
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A kind of soluble phthalocyanine derivative (ZnPc-epoxy derivative) was synthesized, and the influence of C60 on the photoelectric properties of the derivative was studied. The results of ultraviolet-visible (UV-Vis) spectra show that the absorption of the complex is larger than that of the ZnPc-epoxy derivative at B belt. But compared with the derivative, the absorption of the complex decreased at Q belt. The fluorescence spectra show that C60 takes role as annihilation in ZnPc-epoxy derivative. Photo-current tests show that the ZnPc-epoxy derivative-C60 film exhibits increasing photoconductive property. 相似文献
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Novel supramolecular nanocapsules consisting of [60]fullerene and the macrocycle cucurbit[7]uril via self-assembly are reported. The nanocapsules, which were synthesized in a two-phase reaction at room temperature, were obtained in good yields. The stoichiometry of the product was found to be 1:2. 相似文献
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Lamellar hydroxyapatite with worm-like mesopores was successfully synthesized from the mixed ethanol solutions of Ca (NO3)2·4H2O and P2O5 in the presence of polyoxyethylene (20) sorbitan monostearate (Tween-60). The synthesized hydroxyapatite was characterized by means of wide angle X-ray diffraction (WAXRD), small angle X-ray diffraction (SAXRD), electron microscopes and gas absorption. It was found that the content of Tween-60 influenced the crystallinity and the size of lamellar hydroxyapatite, with the volume fraction of Tween-60 increasing the size of HAP lamellasomes increased. The mesopores, around 4 nm in diameter, have a high heat resistance. The mesopore forming templates were from the reactive products of P2O5 and ethanol. 相似文献
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A Novel Method of Distance Measurement Based on Pulse Position Modulation and Synchronization of Chaotic Signals Using Ultrasonic Radar Systems 总被引:2,自引:0,他引:2
Alonge F. Branciforte M. Motta F. 《IEEE transactions on instrumentation and measurement》2009,58(2):318-329
This paper deals with a novel method of transmission and receipt of a signal based on both the property of two chaotic systems generating the same chaotic signal when they are synchronized and the property of pulse position modulation (PPM) to be insensitive to the distortions of the transmission channel. The method is discussed in the context of ultrasonic radar systems, in which the transmitter and receiver, which consist of ultrasonic sensors, are near each other, and the received signal consists of the transmitted signal reflected by an obstacle. A reference sinusoidal signal is superimposed to a chaotic signal generated by a master chaotic system, and the whole signal is modulated according to the PPM method and transmitted by the sensor. The received signal is demodulated, and the demodulated signal forces a slave chaotic system to generate the chaotic signal embedded in it, which allows recovery of the sinusoidal signal by subtracting this chaotic signal from the demodulated echo. The difference of the phases of the reference sinusoidal signal and the recovered sinusoidal signal allows computation of the time of flight of the signal and, consequently, the distance of the radar system from the obstacle. The novel method is illustrated and tested by both simulation and experiments. The interference problem between the considered radar system and other radar systems ( crosstalk) is also addressed, and a solution is proposed to avoid it. 相似文献