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为了满足激光干涉成像,尤其是傅里叶望远镜成像对差频稳定的高功率光学外差干涉模式的需要,提出基于主振功放(MOPA)结构的光学外差干涉激光器的概念,并通过实验验证可行性。从原理上指出现有产生光学外差干涉模式方法的局限性,同时给出基于MOPA结构的光学外差干涉激光器的主要优点。指出基于MOPA结构的激光器可能存在明显影响相干性和产生光频漂移等的限制并设计实验验证。结果表明:功率放大过程对相干性没有明显影响,经过单级功放仍能保持线宽小于0.1 GHz(根据实测相干长度计算线宽约30 MHz),功放过程和倍频过程对光频漂移无影响,实测频漂小于10 Hz,与声光移频器的频率稳定性相吻合,故推知频漂完全由移频器引起。 相似文献
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傅里叶望远镜在对深空暗弱目标成像方面有着独特的优势,但传统的3光束方阵成像扫描时间过长,只能对静止目标成像。为了在几秒之内对运动目标进行高分辨率成像,已经出现了几种不同类型的多光束发射阵列配置方案。在均匀分布排列中,T形配置是目前冗余度最小的结构之一。本文以6光束T形发射配置为例,简单介绍了傅里叶望远镜成像原理,依据T形发射阵列平面与空间频率平面的对应关系,分析了空间频率对成像质量的影响,验证T形发射阵列傅里叶望远镜成像优势,并进行了计算机仿真。得到了不同信噪比条件下的重构图像,通过在相同信噪比条件下和方阵列重构图像对比,成像质量完全满足要求且缩短了成像时间。仿真结果对室内和室外实验有着一定的指导作用,同时也为更多光束及其他发射阵列配置提供了参考。 相似文献
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在微型光学陀螺仪中,声表面波声光移频器是实现系统闭环控制的核心执行器件。本文在理论分析与设计的基础上,以K8玻璃为基片,采用相应工艺成功地研制出声表面波声光移频器样片。经测试,其主要技术指标已初步满足微型光学陀螺仪的设计要求 相似文献
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从速率方程出发,把激光介质的增益带宽以环程频移量为单位划分为若干频带并进行移频处理,仿真分析了基于Nd∶YVO4介质的频移反馈(FSF)激光器在连续输出情况下的特性,给出了在改变抽运功率水平、声光调制器(AOM)衍射效率、环程频移量、介质增益带宽等条件下频移反馈激光器的输出谱宽、频谱位移等的仿真计算结果。实验中,采用端面抽运驻波腔结构并以声光调制器作为腔内移频器,构建了基于Nd∶YVO4介质的全固态频移反馈激光器,实验研究验证了理论计算的结果,并得到了1 W以上的连续激光输出。研究结果表明频移反馈激光器的输出频谱在不同抽运水平下具有谱宽基本稳定的特点。 相似文献
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Golomb Costas序列的结构及其在OFDM系统中的应用 总被引:1,自引:0,他引:1
研究了用循环移位法获得的Golomb Costas序列族的特性,建立了含有一个间隙行和一个间隙列的Golomb Costas序列的结构理论,深入研究了含有一个间隙行和一个间隙列的Golomb Costas序列的代数结构、构造方法和自(互)相关特性,并证明了相关的定理。探索了用含有一个间隙行和一个间隙列的Golomb Costas序列设计OFDM 系统中跳频图样的方法,举例说明了如何设计跳频码和怎样将跳频码分配给 OFDM 系统中的用户。用含有一个间隙行和一个间隙列的Golomb Costas序列设计跳频码能获得理想的自相关特性,并且当无线通信系统中多普勒频移受限时能获得极佳的互相关性能。 相似文献
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针对车载视觉智能感知、低空区域防务等光电成像系统远距离观测动态性能测评需求,研制了室内运动目标模拟系统。基于线性移不变系统模型,分析了“三杆靶”、“四杆靶”靶标MTF测量原理,提出了一种基于变频栅条靶标的动态MTF检测方法,给出了变频靶标设计方案和MTF解算方法。完成了“三杆靶”和变频靶标测量方法的静态和动态MTF对比测试实验。实验结果表明:提出的变频靶标动态MTF检测方法与“三杆靶”测量方法相比,在静态MTF检测时测量数据的相对最大偏差比率为1.9%,动态MTF检测时测量数据相对最大偏差比率为2.8%,是一种高精度数字化动态MTF检测方法。该方法可以从一幅靶标图像中解算出MTF曲线,在动态MTF检测技术领域比“刀口法”、“三杆靶”、“四杆靶”等方法更具优势。 相似文献
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Radiation induced faults in digital systems have started gathering major attention in recent years due to increasing reliability concern for future technologies. For future technologies, multiple transient faults (MTF) originating from a single radiation hit are expected to occur more frequently. Further, due to continuous massive scaling in device geometry, a particle with moderate linear energy transfer (LET) values is expected to affect more than one module/device during striking. Additionally, incessant escalation in operating speed with evolution of technology has increased likelihood of multi-cycle transient (MCT) faults in digital circuits. This calls for novel solutions for concurrently tackling multi-cycle transient and multi-transient fault resiliency at a higher design abstraction level such as behavioral level. This paper proposes a novel approach for generating simultaneous multi-cycle transient and multiple transient fault resilient designs during high level synthesis (HLS) of application specific datapath processors using the framework of dual modular redundancy. Results of the proposed approach on benchmarks indicated generation of low cost MCT–MFT resilient designs during HLS within acceptable runtime. 相似文献
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《Electron Devices, IEEE Transactions on》1981,28(3):251-256
A method is proposed for improving the spatial resolution of frontside-illuminated silicon CCD imagers. The technique involves building the device on an epitaxial layer deposited on a more highly doped substrate of the same conductivity type, creating a high-low junction. A simple theoretical model for the carrier diffusion limited modulation transfer function (MTF) is developed for this structure. Calculations of the MTF using this model are compared to similar calculations for other configurations, e.g., a thinned, backside-illuminated device and a frontside-illuminated imager built on a uniformly doped substrate. The calculations show that the new structure has MTF performance comparable to or better than the backside-illuminated device and has, for λ = 1.06 µm and Nyquist spatial frequency, an MTF which is nearly an order of magnitude higher than that for the nonepitaxial frontside-illuminated device. At the same time, the quantum efficiency of the epitaxial device is reduced by about one order of magnitude. The effects of substrate doping and epitaxial layer thickness are also explored. 相似文献
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Zhonghui Chen Yiwen Xu Weixing Wang Xinxin Feng 《International Journal of Communication Systems》2014,27(10):2022-2029
Power line communication is attracting increasing attention for its characteristics of easy availability and low cost. Frequency shift keying with the virtue of antijamming capability is suitable for the low signal‐to‐noise ratio power line environment. The principle of the frequency shift keying communication system based on momentary Fourier transform (MFT) algorithm is provided first in this paper. Theoretically, the twiddle factor in the MFT algorithm is a decimal with infinite length. However, when it is applied on digital signal processor (DSP), the registers with finite length in DSP lead to the inaccuracy of the twiddle factor. Thus, the MFT algorithm with recursive form will cause accumulative error as a result. We analyze the impact of the inaccurate twiddle factor on the MFT algorithm from a novel point of view, by which the MFT algorithm is considered as a linear time invariant system. We prove that the accumulative error would not disperse when the modulus of the twiddle factor is smaller than 1. Simulation results show that the truncation approach is more effective than both carrying and rounding methods in a practical system. In addition, the number of significant digits of truncated twiddle factor must be chosen larger than 4 to overcome the problem of accumulative error.Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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紫外像增强器是紫外成像系统的核心器件,其成像质量决定了对紫外光学信号的探测和成像能力。调制传递函数(Modulation Transfer Function,MTF)反映了系统对图像不同频率信息的传递能力,是像质评定的一种客观指标。本文基于狭缝成像和傅里叶分析的调制传递函数测试原理,设计了一套紫外像增强器的调制传递函数测试系统。然后对3支紫外像增强器进行了调制传递函数测试实验,得到3支紫外像增强器的MTF曲线截止频率均在32~34 lp/mm之间,并根据MTF曲线对3支紫外像增强器成像质量进行对比分析。最后经过重复测试得到几个重要频率点MTF测试值的标准差均低于0.02。 相似文献
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光学调制传递函数是评价光学系统成像性能的重要指标。以光纤传像束和CCD(CMOS)为代表的离散采样成像器件已经成为高效数字成像系统的重要组成部分。离散采样成像器件对输入光波面是一种线性但不是完全的空间不变过程。MTF的基本原理是系统对空间正弦信号的频率响应。将此类光学系统作为黑箱问题分析,测试系统的频率响应最优方法是选择单频正弦光强图像靶标输入。据此变缺陷为优点,研究利用光栅鬼线结合光学空间二维傅里叶分析,实现连续整数倍频的正弦光强空间波面的提取,得到连续整数倍频的正弦光强图像靶标,并测量了线列光纤狭缝光谱仪系统的MTF,通过测量值拟合获得系统的MTF曲线。 相似文献
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随着现代计量测试仪器的创新发展,基于视觉检测技术和机电控制技术的影像式自动检定设备越来越多的被采用到计量检定工作中,由于线纹量具使用频率较高,难免引起小面积的线纹污损、线纹缺失,虽然大概率情况下并不影响使用,但在检定过程中,通常需要人工对无法识别的线纹进行手动选线,如此一来自动化检定装置则失去意义。本文以目前已投产的"影像式线纹尺检定仪"为项目开展基础,引入近年热点研究领域--人工智能,基于DCC算法进行图像模型聚类分析,基于WGAN算法提出图像修复模型。 相似文献
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针对AOTF成像光谱仪的光谱图像退化程度难以定量化评价的问题,提出了包含后楔角影响的AOTF器件调制传递函数(MTF)定量计算方法。该方法通过建立AOTF的光谱-空间维响应模型获取AOTF器件的线扩散函数(LSF),然后通过线扩散函数傅里叶变换得到理论MTF。在验证实验中,截止频率内的MTF理论值与实测值相对偏差小于15%,可以为AOTF的像质评估提供理论依据。进而,通过该定量计算方法讨论不同AOTF后楔角对光谱图像像质的影响。通过仿真分析得出,AOTF的后楔角难以同时满足横向色差校正与图像退化抑制,需要根据实际应用对于空间分辨率以及横向色差的要求进行取舍。所以,针对AOTF不同后楔角进行光谱图像像质的定量分析对于评估AOTF光谱图像像质具有重要意义,为AOTF器件设计提供了理论依据。 相似文献
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In this work, we develop a method for simulating the modulation transfer function (MTF) of infrared detector arrays, which is based on numerical evaluation of the detector physics. The finite-difference time-domain and finite element methods are used to solve the electromagnetic and electrical equations for the device, respectively. We show how the total MTF can be deconvolved to examine the effects of specific physical processes. We introduce the MTF area difference and use it to quantify the effectiveness of several crosstalk mitigation techniques in improving the system MTF. We then apply our simulation methods to two-thirds generation mercury cadmium telluride (HgCdTe) detector architectures. The methodology is general, can be implemented with commercially available software, has experimentally realizable analogs, and is extendable to other material systems and device designs. 相似文献