共查询到19条相似文献,搜索用时 78 毫秒
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以无线光通信中的副载波调制技术为背景,研究了光强调制正交相移键控信号的循环自相关和循环谱密度函数,并对实际测得的信号的循环谱和循环自相关函数进行了分析。结果表明,无线光副载波信号经过大气传输,同时受到了加性白噪声和乘性窄带随机噪声的影响,有限强度的大气湍流并未破坏正交相移键控信号的循环平稳特性。影响接收信噪比的主要因素是有用信号功率与低频噪声功率之差,通过加时间窗的方法可以有效抑制低频噪声的影响,从而提高系统接收信噪比。 相似文献
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用载波电子散斑与计算机层析技术实现温度场的三维重建 总被引:2,自引:0,他引:2
将载波电子散斑干涉与计算机层析(CT)技术要接合,实现了温度场的三维重建并就这一技术用于三维温度场重建时的各种特性进行了讨论。 相似文献
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大宽高比的非轴对称带状电子注在微波和毫米波真空电子器件中具有显著的技术优势与应用潜力. 采用轴向均匀磁场可以聚焦和传输带状电子注,且具有易于实现电子注与磁场的匹配和调节、聚焦强流电子注以及无传输截止电压限制等优点,但面临严重的Diocotron不稳定性. 结合单粒子模型理论和冷流模型理论,对带状电子注传输特性进行的研究及其数值计算表明,通过详细设计带状注电子光学系统物理参数,增强聚焦磁场并在传输通道高度方向上选择较大的电子注填充比,可以有效降低Diocotron不稳定性对带状电子注的影响,并实现其长距离稳
关键词:
带状电子注
传输
均匀磁场聚焦
Diocotron不稳定性 相似文献
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长周期多载波微放电是近年来新发现的、主要发生在宽带、大功率真空微波部件中的二次电子倍增放电现象. 与发生在单个载波周期中的多载波微放电相比, 长周期多载波微放电来源于多个载波周期间的二次电子累积, 具有相对较低的放电阈值和不可预测性, 对空间和加速器应用中宽带大功率微波部件的长期可靠性带来了新的隐患. 为解决长周期多载波微放电阈值分析中非均匀场激励下二次电子累积的理论计算问题, 本文采用概率方法, 通过引入随机漫步和Branching Levy漫步模型, 对微放电过程中二次电子横向扩散所需遵循的概率模型进行了严格的推导, 并采用所得的概率密度函数, 给出了主模为TE10模的矩形波导中多载波激励下二次电子积累过程的纯理论计算. 与相同条件下采用粒子仿真所得的结果对比, 本文给出的计算结果与仿真结果相符合, 同时计算耗时减少了接近一个数量级. 本文报道的二次电子横向扩散的概率描述可广泛应用于高功率真空电子和电磁器件领域.
关键词:
多载波微放电
二次电子
随机漫步
概率密度 相似文献
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研究了基于双边带载波抑制调制的高频载波信号馈送系统的传输性能.分析了双边带载波抑制调制的原理,系统输出倍频信号的功率以及载波信号经过馈送系统后相位噪音发生劣化的原因.通过实验测量输入载波信号和输出倍频信号的功率和相位噪音验证了理论分析的正确性.结果表明,系统输出倍频信号的功率为-5.7dBm,载波信号经过馈送系统后近端相位噪音劣化了6dB,远端相位噪音劣化了21dB. 相似文献
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研究了基于双边带载波抑制调制的高频载波信号馈送系统的传输性能.分析了双边带载波抑制调制的原理,系统输出倍频信号的功率以及载波信号经过馈送系统后相位噪音发生劣化的原因.通过实验测量输入载波信号和输出倍频信号的功率和相位噪音验证了理论分析的正确性.结果表明,系统输出倍频信号的功率为-5.7 dBm,载波信号经过馈送系统后近端相位噪音劣化了6 dB,远端相位噪音劣化了21 dB. 相似文献
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We show that cosmic strings moving through the plasma at the time of a first-order quark-hadron transition in the early universe
generate baryon inhomogeneities, which can survive till the nucleosynthesis epoch. We find out how these inhomogeneities actually
affect the calculated values of the light element abundances. Recently a wealth of observational data from various experiments
have helped to reduce the uncertainties in the values of these abundances. Using these we show that it is possible to derive
constraints in the presence of cosmic strings during the quark-hadron transition. 相似文献
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Baryon inhomogeneities generated during the quark-hadron transition may alter the abundances of light elements if they persist
up to the time of nucleosynthesis. These inhomogeneities survive up to the nucleosynthesis epoch if they are separated by
a distance of at least a few metres. In this work we present a model where large sheets of these inhomogeneities separated
by a distance of a few km are formed by cosmic string wakes during the quark-hadron transition. The effect of these sheets
on nucleosynthesis will also put constraints on the various cosmic string parameters. 相似文献
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We investigate the influence of an external electric field on the dewetting behavior of nitrogen-water systems between two hydrophobic plates using molecular dynamics simulations. It is found that the critical distance of dewetting increases obviously with the electric field strength, indicating that the effective range of hydrophobic attraction is extended. The mechanism behind this interesting phenomenon is related to the rearrangement of hydrogen bond networks between water molecules induced by the external electric field. Changes in the hydrogen bond networks and in the dipole orientation of the water molecules result in the redistribution of the neutral nitrogen molecules, especially in the region close to the hydrophobic plates. Our findings may be helpful for understanding the effects of the electric field on the long-range hydrophobic interactions. 相似文献
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We study the possibility of probing high scale phase transitions that are inaccessible by LIGO. Our study shows that the stochastic gravitational-wave radiation from cosmic strings that are formed after the first-order phase transition can be detected by space-based interferometers when the phase transition temperature is \begin{document}$ T_n\sim {\cal{O}}(10^{8-11}) $\end{document} ![]()
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GeV. 相似文献
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A.T. Asvini meenaatciR. Rajeswarapalanichamy K. Iyakutti 《Physica B: Condensed Matter》2011,406(17):3303-3307
First-principles calculation was performed using tight-binding LMTO method with local density approximation (LDA) and atomic sphere approximation (ASA) to understand the electronic properties of rhenium nitride. The equilibrium geometries, the electronic band structure, the total and partial DOS are obtained under various pressures and are analyzed in comparison with the available experimental data. The most stable structure of ReN is NiAs like structure. Our results indicate that ReN can be used as a super-hard conductor. We estimated the average electron-phonon coupling constant to be 1.65 and superconducting transition temperature (Tc) is 5.1 K. The Tc value increases with the increase in pressure. 相似文献