共查询到20条相似文献,搜索用时 62 毫秒
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高码率是我国运载火箭遥测系统PCM-FM体制未来发展方向之一。为解决高码率数据传输过程中出现的无线作用距离下降和基带传输距离不足的问题,参考目前通信领域的技术发展前沿,提出了采用多符号检测(MSD)和Turbo乘积码(TPC)技术解决高码率遥测无线作用距离下降的方案,可在保持箭上发射机输出功率和地面接收天线直径不变的情况下额外获得约6dB的信道增益,确保测量数据通信正确可靠。同时采用了多级树形拓扑结构、新型基带通信协议和帧格式设计方法解决了高码率条件下基带数据传输距离不足的问题,并以某新型运载火箭为例,给出了高码率遥测系统的组成构架结构。 相似文献
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系统是为某型号新一代航天载荷可见光通道设计;主要功能是实现可见光通道的图像的实时采集与获取,完成可见光通道的地面调试与性能检测;文中针对测试需求提出了完整设计方案和软硬件实现方法;系统采用Xilinx新一代低功耗现场可编程门阵列(FPGA)作为控制核心,通过自顶向下的程序设计方法完成硬件时序驱动和逻辑控制;系统主要完成了机械接口设计,CMOS探测器的电路设计与时序驱动,光电压信号的放大、滤波与数模转换,图像数据与上位机的传输接口设计以及上位机软件设计;高速数据传输通过USB接口来实现;经测试验证,系统功能良好,能很好地满足实际工程需求。 相似文献
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新一代运载火箭时序仿真系统具有数字电路速度快、集成度高的特点,系统要求发出多路高精度时序、时串信号以满足新一代运载火箭地面测试设备的检查与校准需求,因此信号完整性问题在系统设计中不容忽视。针对仿真系统的典型模块(USB 3.0 Super-speed差分线、FPGA外设数据走线、时钟走线)进行建模分析仿真得出PCB硬件电路设计参数,给出时序仿真系统设计信号完整性问题的抑制和解决方法,优化了板级信号质量,改善系统可靠性、工作连续性和输出精度,可有效提高新一代运载火箭测试效率和测试可靠性。 相似文献
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高可靠的测试网络作为运载火箭远距离测发控的基础平台,是实现运载火箭地面远距离测试发控的重要技术保障。通过对运载火箭地面测发控网络架构深入研究,采用国产商用网络设备搭建原型平台、开展原理性验证试验,经过反复试验,不断改进技术方案,解决了冗余热备网络协议选用、冗余故障切换、故障切换实时性、网络可靠性等技术难题,提出了基于国产化设备的网络架构设计方案。对网络架构的工作原理、可靠性、实时性、安全性进行了详细分析。建立的国产化高可靠网络架构,不仅能够应对复杂的火箭测试现场,使网络平台具有更好的可靠性、实时性、扩展性和灵活性,更进一步提高了网络的安全性。设计的国产化网络平台架构可用于运载火箭地面测发控网络使用。 相似文献
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为了提高固体火箭发动机系统的动态交互能力,方便用户直观地了解固体火箭发动机的内部结构,结合CATIA强大的三维建模能力,完成了该系统中最重要的三维参数化设计;以VC++为编程环境,运用CATIA自动化对象编程(V5 Automation)提供的二次开发接口,实现了固体火箭发动机系统中的三维绘图模块,同时介绍了两种在VC框架内动态显示CATIA三维模型的方法;实践证明,该系统能够快速的确定固体火箭发动机外形尺寸、标志量等设计参数,为固体火箭发动机的初步设计提供有效的帮助。 相似文献
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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. 相似文献
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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. 相似文献
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A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands. 相似文献
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40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm. 相似文献
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Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser. 相似文献
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Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored. 相似文献
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Xin Kang 《中国光学快报(英文版)》2008,6(2)
An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography. 相似文献
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The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films. 相似文献
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References: 《声学学报:英文版》2008,27(1):85-96
Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation. 相似文献