共查询到20条相似文献,搜索用时 598 毫秒
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完成了调制气流声源阵列的相干合成实验. 提出了利用主动相位控制方法实现调制气流声源阵列相干合成的思路, 介绍了基于随机并行梯度下降算法的声源阵列相干合成的原理. 对利用该算法实现声源阵列的相干合成进行了数值模拟, 完成了双调制气流声源阵列在远场的相干合成实验, 并给出算法参数的合理设置方案. 实验结果显示, 基频成分的相干合成效果明显, 算法收敛时测点处的声压级相比单源发射增加了4 dB, 接近于各单源功率谱中基频成分相干合成、其他频率成分非相干合成的结果; 结果表明实验中算法能够有效控制各调制气流声源辐射声波的相位, 取得了明显的相干合成效果.
关键词:
调制气流声源
相干合成
随机并行梯度下降
高阶谐波 相似文献
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基于功率谱分析的指纹实时识别系统 总被引:3,自引:2,他引:1
把实时获取指纹的装置与功率谱分析系统结合起来,实现完整的指纹实时识别系统.从实验上研究了相干光源和非相干光源获取指纹的两种情况.实验表明,用非相干光源获取指纹的情况具有较好识别效果. 相似文献
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在对相干偏振复用四相相移键控信号进行偏振解复用的实时相干接收机中,为高效补偿偏振效应,同时降低系统对时钟频率要求与系统中FPGA资源的使用量,对接收机中广泛采用的恒模算法从并行性、滤波器阶数、以及流水性3方面进行了研究改进,提出了并行流水型恒模算法.研究结果显示,在43Gb/s高速相干接收系统中,相干接收机的并行度宜为32,滤波器阶数宜为5.VPI与MATLAB联合仿真结果表明,采用本文提出的并行流水型恒模算法后,基于FPGA的四相相移键控信号实时相干接收机对时钟频率的要求可以降低到168MHz;在不丢包的情况下,系统能够处理43Gb/s相干接收系统中的全部数据,有效实现偏振解复用;在背靠背情况下,补偿1×10-3误码率的OSNR为14.5dB.利用高层次综合软件将并行流水型恒模算法下载到FPGA中,DSP资源的使用量仅仅是传统算法使用量的1/8. 相似文献
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低相干光源干涉系统在大口径拼接子镜间相位误差检测上的应用 总被引:1,自引:0,他引:1
针对大口径望远镜拼接式主镜,提出一种基于迈克耳孙干涉原理的低相干光源干涉检测系统.应用该系统对拼接子镜间相位失调误差进行实时检测.进而对失调子镜进行相应校正,以实现拼接子镜的共面排布.给出了低相干光源干涉检测系统的具体结构,叙述了干涉检测系统的检测原理,提出应用双中心波长组合低相干光源进行拼接子镜间相位误差检测,分析了系统最低信噪比.结果表明,双中心波长组合低相干光源系统,可以提高低相干光源下涉中心条纹的信号分辨能力.借以提高检测精度.使得低相干光源干涉测量系统对拼接子镜间的相位失调误差进行高精度提取. 相似文献
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针对大口径望远镜拼接式主镜,提出一种基于迈克尔逊干涉原理的低相干光谱干涉检测系统.应用该系统对拼接子镜间相位失调误差进行实时检测,进而对失调子镜进行相应校正,以实现拼接子镜的共面排布.子镜间相位误差通过干涉图形间的不匹配性进行提取.给出了该低相干光谱干涉检测系统的具体结构,叙述了该干涉检测系统的检测原理.针对该系统的干涉条纹对比度V及系统的最低信噪比SNRdBmin进行了分析,论证了通过该低相干光谱干涉检测系统进行子镜间相位误差检测的可行性. 相似文献
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基于相干态和信号位的光子数态与弱交叉Kerr非线性相互作用后,会在相干态上产生相位变化,并结合极化分束器构造了一个奇偶校验测量装置.用零差探测器对相干态的相位变化进行测量,实现对Bell态的非破坏区分.再利用控制非门和斜置的极化分束器对两信号位光子进行控制非操作和单光子测量,完成对四个Bell态的完全区分.用到的弱交叉Kerr非线性增加了区分方案在实验上实现的可行性. 相似文献
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载波全息干涉图的自动分析 总被引:1,自引:0,他引:1
用正交相干相位检测法实现了载波全息干涉图的自动分析.讨论了分析载波条纹图的边界效应,提出了一种易于在微机上实现的条纹图外插算法.最后给出了一幅实时法载波全息图的分析结果. 相似文献
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The monodisperse polystyrene spheres are assembled into the colloidal crystal on the glass substrate by vertical deposition method, which is aimed at the so-called photonic crystal applications. The structural information of the bulk colloidal crystal is crucial for understanding the crystal growth mechanism and developing the various applications of colloidal crystal. Small-angle X-ray scattering (SAXS) technique was used to obtain the bulk structure of the colloidal crystal at Beamline 1W2A of BSRF. It is found that the SAXS pattern is sensitive to the relative orientation between the colloidal sample and the incident X-ray direction. The crystal lattice was well distinguished and determined by the SAXS data. 相似文献
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The growth rates of edge-on lamellar polymer crystals in variable thickness films were investigated in terms of dynamic Monte Carlo (MC) simulations. The growth rates linearly decreased with decreasing film thickness for the thinner films and were nearly constant for the thicker films. The mean stem lengths (crystal thickness) were also constant in different thickness films. The crystal widths parallel to the film thickness increased more slowly with increasing film thickness in the thinner films than that in the thicker films, indicating they were restrained by the film thickness. We propose that the growth rate of edge-on lamellar crystals in thin films is dominanted by the crystal width in the thinner films and by the crystal thickness in the thicker films; the variation of the film thickness can change the three-dimensional shape of the crystal growth front, also affecting the growth rate of the edge-on lamellar crystal. 相似文献
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小尺寸单轴应变Si p型金属氧化物半导体(PMOS)沟道反型层迁移率与晶面/晶向密切相关,应变PMOS优化设计时应合理选择沟道的晶面/晶向.目前,文献已有1.5 GPa应力强度下单轴应变Si PMOS沟道反型层迁移率按晶面/晶向排序的理论模型.然而,在器件实际制造过程中,覆盖SiN应力膜工艺是固定的,由于沟道弹性劲度系数具有各向异性,这样,不同晶面/晶向应变PMOS沟道所受应力强度不同,进而导致在实际工艺下沟道反型层迁移率晶面/晶向排序理论模型"失效".针对该问题,本文采用中国科学院微电子研究所40 nm工艺流程制备了不同晶面/晶向40 nm沟道小尺寸单轴应变Si PMOS与未应变Si PMOS,并通过器件转移特性测试,获得了小尺寸单轴应变Si PMOS反型层迁移率晶面/晶向排序结论.此有关小尺寸单轴应变Si PMOS沟道反型层迁移率晶面/晶向排序的相关结论,由于考虑了工艺实现因素,与文献理论预测排序结果相比,更适于指导实际器件制造;相关分析方法也可为其他应变材料沟道MOS相关问题的解决提供重要技术参考. 相似文献
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Charged colloidal suspensions have been used as experimental models for the study of crystal nucleation. Here we propose that the technique of template-assisted colloidal self-assembly can be used to visualize the effects of defect propagation in atomic crystal films produced using epitaxial growth. Templates with periodic line defects were used to grow [100]-oriented three-dimensional photonic crystals by means of the template-assisted colloidal self-assembly method, aided by capillary and gravitational forces. The defect propagation in the [100]-oriented photonic crystal was observed using scanning electron microscopy, both at the surface of the crystal and on cleaved facets. This method is useful in the understanding of defect propagation in the growth of colloidal films on templates - and the same approach may also prove useful for the understanding of atomic crystal growth on substrates with defects. Additionally, the deliberate incorporation of line defects may prove valuable as a way of introducing waveguide channels into three-dimensional photonic crystals. 相似文献
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Single crystals of the nonlinear optical material glycine thiourea were grown by the slow evaporation technique. The crystal structure and lattice parameters were determined for the grown crystal by the single crystal X-ray diffraction studies. Single crystal XRD revealed that the material crystallized in a monoclinic crystal system. Optical studies have been carried out and it was found that the tendency of transmission observed from the specimen with respect to the wavelength of light, is practically more suitable for opto-electronic applications. The dielectric constant, dielectric loss and ac conductivity of the compound were calculated at different temperatures and frequencies, to analyze the electrical properties. The photoconductive behavior of the material is also investigated and the results are discussed. 相似文献
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说明了Interleaver的基本原理,分析了晶体型Interleaver的滤波片的原理,以YVO4晶体为例,给出了具体应用的设计思想。 相似文献