一种有源相控阵天线误差补偿方法

为了消除由于有源相控阵天线单元间互耦、天线的安装误差、天线方向图的不一致性和天线罩的影响等导致天线校正时与实际天线单元间幅相值存在的差异,采用了一种有源相控阵天线误差补偿方法,获得天线的误差值并保存在雷达校正计算机中,雷达进行校正时调用该值从而很好地消除了上述因素导致的在雷达使用中带来的影响,较好地改善了天线校正的幅相值和波瓣图,保证了雷达实际使用中达到预期指标要求。     

高Yb~(3+)/Er~(3+)掺杂的磷基有源光纤材料的光谱性质

研究了Yb3+/Er3+共掺60P2O5-15BaO-10Al2O3-5ZnO-10R2O(R=Na,K)以P2O5为主体的磷基有源光纤材料的光谱性质,以及不同Yb3+/Er3+掺杂浓度对光谱性质的影响规律。当Er3+浓度为9.100×1019/cm3、Yb3+的掺杂浓度为5.407×1020/cm3、Yb3+/Er3+浓度比为6∶1时,玻璃样品在1 531 nm处的受激发射截面最大,为6.17×10-21cm2。同时,其荧光寿命为9.73 ms,荧光半高宽为53.16 nm,发射截面与半高宽的乘积为3.28×10-32m3,综合性能最佳。     

同体对偶变换与不存在磁单极子的理论分析

通过同体对偶变换,讨论了没有磁单极子的电磁对称性.     

Acoustic anechoic layers with singly periodic array of scatterers: Computational methods,absorption mechanisms,and optimal design

The acoustic properties of anechoic layers with a singly periodic array of cylindrical scatterers are investigated. A method combined plane wave expansion and finite element analysis is extended for out-of-plane incidence. The reflection characteristics of the anechoic layers with cavities and locally resonant scatterers are discussed. The backing is a steel plate followed by an air half space. Under this approximate zero transmission backing condition, the reflection reduction is induced by the absorption enhancement. The absorption mechanism is explained by the scattering/absorption cross section of the isolated scatterer. Three types of resonant modes which can induce efficient absorption are revealed. Due to the fact that the frequencies of the resonant modes are related to the size of the scatterers, anechoic layers with scatterers of mixed size can broaden the absorption band. A genetic optimization algorithm is adopted to design the anechoic layer with scatterers of mixed size at a desired frequency band from 2 kHz to l0 kHz for normal incidence, and the influence of the incident angle is also discussed.     

A new shunt DC active filter of power supply in a steady high magnetic field facility

A DC active power filter is an indispensable part in a high power and high stability power supply system, especially in the power supply system of the Steady High Magnetic Field Facility, which requires that the current ripple should be limited to 50 parts per million. In view of the disadvantages of the series DC active power filter and shunt Pulse Width Modulation DC active filter, this paper puts forward a novel DC active filter by combining the advantages of the transistor regulator and the shunt type. The structure and principle of the new shunt linear active filter are introduced. Meanwhile, the design of several key components that construct the new shunt linear active filter is also analyzed. The simulation model and an experimental prototype of the shunt linear active filter are developed, and the results verify that the parameter design is reasonable and the shunt active filter has a good filter effect.     

隐声衣结构设计和实验研究新进展

隐声衣是一项使物体隐藏于声场的新技术,与传统吸声方式相比,隐声衣消除回波时不会在目标背后留下声影区。隐声衣的物理实现是重点研究方向之一,利用具有特殊性质的材料或结构消除散射是获得隐声效果的主要途径。文章综述了隐声衣研究在结构设计和实验方面的几项新发展。包括基于超常材料的隐声衣、基于温度递度的隐声衣、应用反演设计方法的隐声衣、有源隐声衣等,主要介绍隐声衣机理和结构设计方面的新思想,以及新型人工材料和人工结构在隐声衣研究中的应用。     

激光输出功率随耦合率及放大率的变化规律

建立了涵盖稳定腔和非稳腔的激光有源理论模型和激光开式谐振腔的边界条件。根据定态薛定谔方程与亥姆霍兹方程的等价性,采用量子力学方法求解谐振腔的亥姆霍兹波动方程,得到满足方程、边界条件、矩阵光学、稳定条件的本征解和本征方程。根据本征方程推导出横模数目随耦合率变化的规律,进而推导出激光输出功率随耦合率变化公式,以及激光输出功率随放大率的变化规律。该理论模型能够从稳定腔自然过渡到非稳腔,在小耦合率情况下退化到与传统公式基本一致的形式,又能在大耦合率情形下与实验结果符合得很好。     

管道有源噪声控制中壁面分布次级声源的空间分布优化

为了改进管道中高阶模式声波的有源控制效果,研究了壁面分布次级声源的空间分布优化问题。首先提出管道中次级声源独立控制高阶模式声波的理论模型,然后推导次级声源在管道中各方向上空间分布对控制高阶模式声波的贡献,得到了次级声源空间分布的优化准则。通过将空间分布离散化,采用最小化管道中声能流的控制策略得到次级声源的最优驱动强度,最后通过数值仿真对比最优驱动强度时各种次级声源空间分布对控制性能的影响,验证了通过优化次级声源空间分布能显著提高控制效果。仿真结果表明,当次级声源分布于管道所有壁面且沿管道轴向分布范围较大时,高阶模式的控制效率最高。     

噪声有源控制系统的性能预测

研究有源噪声控制中系统性能的实验预测方法,通过原理分析表明利用原始声场和次级声通道传递函数测试数据,能够预测有源噪声控制系统的性能并优化设计系统;结合飞机舱内的应用实际,给出了有源噪声控制系统性能预测和优化设计的基本方法和过程。该方法已被应用于国产运七飞机舱内噪声有源控制实验,取得了满意的结果。     

利用正弦调频信号的宽带速度敏感特性抑制混响

有源声呐探测水中低速目标时,混响与目标回波的频率接近,目标回波与混响分离困难.根据运动目标与产生混响的散射体在速度域的差异,利用正弦调频信号(SFM)的速度敏感特性实现目标回波与混响的有效分离.推导了 SFM信号宽带混响抑制能力与速度分辨模糊之间的约束关系,建立了波形优化设计的搜索模型.通过多普勒滤波处理将数据从频率域...