球面非探针校准近—远场变换

采用球面波展开方法实现“近－远”场变换。对矩形角锥嗽叭天线球面近场扫描测量的数据进行了近远场变换，得到与实测的远场十分吻合的变换远场。     

天线近远场变换的快速算法

基于考虑探头补偿的平面近远场变换理论,根据实际需要,提出了一种工程实用的平面近远场变换快速算法。通过该算法由近场测量数据变换得到的天线远场方向图,既能达到任意分辨率,又能节约计算内存和提高计算速度。     

平面近远场变换的快速算法

基于考虑探头补偿的平面近远场变换理论 ,根据实际需要 ,提出了一种工程实用的平面近远场变换快速算法。通过该算法由近场测量数据变换得到的天线远场方向图 ,既能达到任意分辨率 ,又能节约计算内存和提高计算速度。     

球面探针校准近—远场变换

从探讨校准信息的传输方程出发，对天线球面扫描测量的数据进行球面近、远场变换。阐述了用这种变换方法实现“近-远”、“近-近”、“远-近”和“远-远”四种变换的措施，其中对矩形角锥喇叭天线球面扫描测量的数据进行了“近-远”和“远-近”场变换，变换结果与测量结果吻合较好。     

近远场变换中的模糊相位恢复与远场重建

本文用泛函方法探讨了仅用近场振幅数据进行了近远场变换的相位逆问题。推导出了一组非线性方程，使一曲面上场相位与此曲面及另一曲面上场振幅的关系一目了然，所建立的目标泛函属于实空间，形式简洁易于处理，减少了数据量。数值结果表明，当相位初值在解的附近时，相位能得到恢复。     

天线平面近场测量中一种近远场变换方法研究

本文研究了一种应用于天线平面近场测量中完成近远场变换的数值算法。利用此方法可以依据天线平面近场测试数据快速简便地求得天线远场方向图及其它特性,其精度较高;同时可以很方便地进行探头修正,并讨论天线平面近场测试中各关键参数对测试结果的影响。本文给出了理论依据和具体计算实例,与传统方法进行了比较,并得出了结论。     

球模式展开理论近远场变换及快速算法

基于球模式展开理论的近远场变换是天线球面近场测量系统实现的关键,它将待测天线在空间建立的场展开成球面波函数之和,由于其计算公式复杂,因而计算耗费时间长。该文在实际计算中利用快速傅里叶变换及矩阵的思想可以大幅度提高程序运行速度,节省计算时间。采用该方法对角锥喇叭天线的近远场数据进行仿真验证,结果表明外推远场的结果和理论值吻合良好,说明了该方法在保证计算精度的同时,可缩短计算时间。     

FDTD中近远场变换计算天线方向图的新方法

针对FDTD中时域近远场外推求方向图的方法运算量太大的缺点,提出一种在时域迭代中对等效面上的场进行傅立叶变换,时域迭代完后得到频域场,再进行频域近远场变换求天线方向图的方法。对该方法的消耗额外内存和消耗额外机时(相对于仅算近场而言)进行分析,数值试验表明,该方法的优点是计算量小而且简单。     

基于基尔霍夫积分的近远场变换的改进

改进了ＦＤＴＤ中基于Ｋｉｒｃｈｈｏｆｆ积分的近远场变换。它的优点在于实现简单,计算某一远场分量只用到与之相同的近场分量,。既能计算远场又能计算近场,可以大大缩减ＦＤＴＤ计算空间。同时将每一时间步的近场对远区的贡献分别计算,避免了存储积分面上上一时间步近场值的内存开销,近远场变换得到了进一步简化。计算结果表明,这种变换方法非常准确。     

Improved algorithm for probe-corrected spherical near-field/far-field transformation

The technique for computation of antenna far fields from spherical near-field measurements has been improved, allowing large antennas to be treated. The efficiency and accuracy is demonstrated for an antenna without rotational symmetry and about 50 wavelengths in diameter.     

Exact surface impedance for a spherical conductor

A spherically concentric model of the earth is employed to obtain expressions for the surface impedance matrix at the surface. It is shown the surface impedance is a function of both the earth's electrical parameter and the source field configuration. In some cases the latter dependence is of minor consequence.     

Radial field retrieval in spherical scanning for currentreconstruction and NF-FF transformation

A near-field to far-field (NF-FF) transformation is addressed for the case of spherical scanning using equivalent magnetic currents (EMCs) and matrix methods. It is based on the decoupling of the field components and the iterative retrieval of the radial component of the electric field. The technique is applied for far-field calculation as well as for the estimation of the current distribution of the antenna under test (AUT) using spherical near-field facilities. Results from measured near-field data of several antennas are presented and compared to those of the analytical solution via a spherical wave mode expansion method     

高斯光束经球端面抛物型GRIN棒传播与变换特性分析

本文采用矩阵光学的方法,分析了高斯光束经球端面抛物型梯度折射率棒透镜的传播与变换特性.     

球状光纤耦合器参数与耦合效率的关系

根据光线追迹方法,通过计算和推导,讨论了在制作和设计球状光纤耦合器时应该注意的参数设计,得到其参数与耦合效率的解析表达式,为球状光纤耦合器的设计提供了理论计算依据。     

Threshold discrimination and blanking for large near-far power ratios in UWB networks

A simple chip-discrimination technique is presented for use with ultra-wideband (UWB) impulse radio (IR) that improves performance for large near-far interference power ratios. A typical spread-spectrum IR that employs a matched-filter sum for bit decisions is susceptible to small numbers of large power pulses that can dominate the bit decision-threshold statistics. This letter describes a technique for chip discrimination prior to the spreading summation, that can greatly reduce the effects of large near-far power ratios among interferers. The technique exploits the very narrow pulsewidth and resulting low-duty-cycle characteristic only achievable with ultra-wide bandwidth. A statistical model is developed that predicts bit-error performance for binary offset pulse position modulation as a function of near-far density and power for varying discrimination thresholds. An analytic solution for perfect chip blanking is developed, and is in good agreement with chip discrimination for large near-far power ratios. We find that even a small number of very near interferers can greatly reduce the performance of a system without blanking or discrimination. Results show substantial improvement using this method for near interferers with near-far power ratios greater than 20 dB.     

Analysis of an adaptive SIC for near-far resistant DS-CDMA

A new multiuser detection scheme is proposed which employs adaptive minimum mean square error (MMSE) detection in combination with successive interference cancellation (SIC). Through theoretical analysis and numerical examples, it is shown that the proposed detector provides superior performance to existing ones in terms of asymptotic multiuser efficiency (AME) and bit error rate (BER)     

A fast learning algorithm for Gabor transformation

An adaptive learning approach for the computation of the coefficients of the generalized nonorthogonal 2-D Gabor (1946) transform representation is introduced. The algorithm uses a recursive least squares (RLS) type algorithm. The aim is to achieve minimum mean squared error for the reconstructed image from the set of the Gabor coefficients. The proposed RLS learning offers better accuracy and faster convergence behavior when compared with the least mean squares (LMS)-based algorithms. Applications of this scheme in image data reduction are also demonstrated.     

数字视频信号矩阵变换算法中的折衷处理

由于降低成本和高清晰度电视接收机小型化的要求，视频信号的矩阵变换电路（芯片）也相应地要减少面积和少占用资源，但同时又不能过多地降低转换结果精度，这就存在一个矛盾。通过用可编程逻辑器件（ＥＰＬＤ）经过多次计算机模拟实验，得到了如何在这两者之间了得最好折衷的办法。     

球面旋涂胶层厚度分布模型及其实验研究

创建一种光刻胶离心式旋涂过程中基于流体力学分析的凸面胶厚分布及胶厚均匀性模型,根据曲面流体运动方程以及凸面基片的面型特征得到了凸面恒速甩胶过程中胶层厚度的分布公式,结合凸面流体层流条件和牛顿流体的质量连续方程推导出胶厚分布与胶液类型、初始胶液粘度和密度、转速、基片几何尺寸以及甩胶时间等参数的关系式,利用光谱椭偏仪和台阶仪所测得的结果对该模型进行了验证,两者有较好的吻合,同时建立了胶厚均匀性与甩胶转速、甩胶时间的关系式,该模型可跟踪、监控和改进预光刻过程中凸面胶层的均匀性,以便改善最后的光刻线条质量。