抛物线方程中不规则地形的分段线性模型的研究与验证

主要研究了对流层电波传播过程中起伏地形的处理方法。阐述了抛物线方程中阶梯地形方法和分段线性方法,提出了新的初始场设置方法,并给出了算法。利用该方法,仿真计算了尖劈地形下电磁波传播问题,并与射线法和UTD方法的计算结果进行了比较。计算结果显示了分段线性方法的优越性。     

如何设计HFC网光分路器的分光比

本文简要介绍了光分路器的主要技术指标。并重点介绍了在HFC网中如何设计光分路器的分光比。包括光分比的常用计算方法和根据不同应用对常用计算方法进行改进后计算方法。并对这些计算方法进行了比较。     

一种计算毫米波微带天线阵馈线损耗的方法

微带阵列天线增益的计算必须计入微带线损耗才有可靠精度,为此提出了一种计算毫米波微带天线阵整体馈线损耗的方法,导出了256元并馈阵、192元串并馈阵的损耗计算表达式,计算值与现有实测值相比较证实了本方法的有效性。     

偏置抛物环面天线增益的计算

本文给出了偏置抛物环面天线增益的两种计算方法和计算公式,并把两种方法的计算结果和文献(1～3)中的测试值或计算值进行了比较,表明其中一种方法的计算结果更加精确。     

FDTD方法在磁共振射频线圈仿真中的应用

本文提出了磁共振射频线圈电磁场仿真计算的FDTD方法,并对该方法中的仿真计算稳定性和边界吸收条件等关键技术的实现进行了详细阐述.利用这种方法,本文对磁共振鸟笼线圈的电磁场进行仿真计算分析,并给出了电磁场分布的仿真计算结果,仿真结果与鸟笼线圈的实际电磁场分布相吻合.     

激光加热温度场的简化计算

本文计算分析了激光加热金属的简化计算方法,并指出了简化计算的适用条件。     

基于ADI-FDTD的混合方法及其快速算法

该文介绍了FDTD与ADI-FDTD相结合的方法,提出了减小因两种不同计算方法在边界引起反射的加权平均的方法,并给出了ADI-FDTD计算线性、无耗、各向同性媒质的快速算法.计算结果表明了该方法的有效性.     

舰艇短波通信干扰距离的计算

针对常用通信干扰距离估算方法精度不高、适应性不强且不便于利用计算机计算的问题,以短波场强计算为基础,结合舰艇通信对抗战术计算方法,推导并给出了地波最大干扰距离、天波最小和最大干扰距离的计算模型、方法和步骤,对模型进行了仿真,并通过定性分析和与实际数据的定量对比分析,验证了模型的准确性和实用性,为实际应用中利用计算机估算有效通信干扰距离提供了有效可靠方法。     

有效折射率法的研究

分析了有效折射率法及其计算偏差的产生原因,提出了一种改进方法。这种方法克服了有效折射率法的由计算顺序不同导致的计算结果不一致的问题,并使计算精度有所提高。     

蓄电池组放电时间的计算

主要讨论了蓄电池组放电时间的计算方法，并详细阐述了影响蓄电池组放电时间计算准确性的因素，最后给出了一种较为准确地计算蓄电池组放电时间的方法。     

Numerical method for calculating surface current density on a two-dimensional scatterer with smooth contour

A numerical method is presented for finding the surface current density on a two-dimensional smooth scatterer. This method is an improved version of a method which one of the authors presented as an adjoint method to the conventional mode-matching method (MMM) for finding the scattered field. After formulating the problem, we interpret the method being adjoint to the conventional mode-matching method and show that the method yields a sequence of approximate current densities converging to the true density in the mean squares sense. Next we propose the improved method and prove the fact that this method yields a sequence of approximate solutions which converges to the true density uniformly on the contour of the scatterer. We then state that the method is an adjoint one to the mode-matching method with a smoothing procedure (SP) which we proposed as a powerful numerical method for the scattered field. Numerical results of some sample calculation are attached to show the effectiveness of the new method.     

A genetic algorithm for the inverse problem in synthesis of fibergratings

A new method for synthesis of fiber gratings with advanced characteristics is proposed. By combining the Runge-Kutta method for calculating the reflection spectrum of a fiber grating and a genetic algorithm, we obtain a promising method for the synthesis. Compared to other methods, the proposed method facilitates the task of weighting the different requirements to the filter spectrum. In addition, the method is general, and would thus be useful for other inverse problems     

The application of the conjugate gradient method for the solution of electromagnetic scattering from arbitrarily oriented wire antennas

The method of conjugate gradients is applied to the analysis of radiation from thin-wire antennas. With this iterative technique, it is possible to solve electrically large arbitrarily oriented wire structures without storing any matrices as is conventionally done in the method of moments. The basic difference between the proposed method and Galerkin's method, for the same expansion functions, is that for the iterative technique we are solving a least squares problem. Hence, as the order of the approximation is increased, the proposed technique guarantees a monotonic decrease of the least squared error (parallel AI - Yparallel^{2}), whereas Galerkin's method does not. Even though the method converges for any initial guess, a good one may significantly reduce the time of computation. Also, explicit error formulas are given for the rate of convergence of this method. Hence, any problem can be solved to a prespecified degree of accuracy. It is shown that the method has the advantage of a direct solution as the final solution is obtained in a finite number of steps. The method is also suitable for solving singular operator equations in which case the method monotonically converges to the least squares solution with minimum norm. Numerical results are presented for the thin-wire antennas and are compared with the solution obtained by the method of moments.     

含逻辑门的武器系统效能评估方法研究

在模糊综合评判和灰色聚类评价法中,各个指标间总是采用单一的线性加权的方法.为了充分体现各个指标间复杂的聚合关系,排除“一票否决”式指标对总体效能的影响,借鉴逻辑门思想,加入了“与”、“或”逻辑关系.通过实例验证,证明了方法的可行性,解决了“一票否决”式指标对评估方法的影响;同时也为现有评估方法的改进提供了有益的参考.     

Voltage Induction Method for Microwave Susceptibility Measurements

A voltage induction method of microwave susceptibility measurement has been proposed. A signal from a one-turn coil wrapped directly on a magnetic sample is phase sensitively detected, and the real and imaginary parts of susceptibility as a function of magnetic field are directly indicated on an oscilloscope. Analysis shows this method to have a much higher sensitivity for small samples than the conventional cavity perturbation method. Also, this method is characterized by a higher stability, since the measurement is not for the perturbation of the resonant curve of high Q cavity, but for RF magnetic flux in a sample which is relatively stable for a frequency fluctuation of the signal source, independent of the sample volume. This method has been checked with good agreement against a perturbation method for a sample where both methods could be used. A YIG film, which is too small (4 mm by 4 mm by 0.3/spl mu/) to obtain any detectable perturbation of cavity parameters, was successfully measured by this method. The new method allows very rapid measurement combined with a very simple procedure for the relative measurement of susceptibility.     

The effective index method and its application to semiconductor lasers

By the effective index method a two-dimensional field problem is transformed to a problem for a one-dimensional effective waveguide. This method is applied to semiconductor lasers having a gradual lateral variation in the complex permittivity. For the special case of a parabolic variation, analytical formulas for the required gain in the center and the half width of the intensity distribution are derived. The results are compared with a numerical method and very good agreement is found except in some cases where convergence problems occur for the numerical method. This agreement is taken as evidence for the validity of results obtained using the effective index method for analysis of semiconductor laser structures.     

Model-Based Satellite Image Fusion

A method is proposed for pixel-level satellite image fusion derived directly from a model of the imaging sensor. By design, the proposed method is spectrally consistent. It is argued that the proposed method needs regularization, as is the case for any method for this problem. A framework for pixel neighborhood regularization is presented. This framework enables the formulation of the regularization in a way that corresponds well with our prior assumptions of the image data. The proposed method is validated and compared with other approaches on several data sets. Lastly, the intensity-hue-saturation method is revisited in order to gain additional insight of what implications the spectral consistency has for an image fusion method.     

Carrier-Based Modulation Technique for Matrix Converter

This paper presents a carrier-based modulation method for a matrix converter. By using the offset voltage and changing the slope of carrier, it is possible to synthesize the sinusoidal input currents with the unity power factor and desired output voltages. The proposed method is equivalent to the so called space vector pulsewidth modulation method. The proposed method uses a new point of view to understand the matrix converter modulation method such as the voltage source inverter (VSI) modulation method. Using the proposed method, this paper presents the two-phase/three-phase modulation method and dynamic/steady-state overmodulation method for the matrix converter. These methods are well developed in the study of a VSI. By the proposed steady-state overmodulation method, it is possible to synthesize the fundamental component of output voltage to be equal to that of input voltage at the cost of some distortion of input current. The feasibility of the proposed modulation method has been verified by a computer simulation and experimental results. These results show that the proposed carrier-based modulation method can be implemented easily without any tables. It can be used for the application where a higher voltage transfer ratio is essential     

Direct G/T Measurement for Satellite Broadcasting Receivers

A new G/T measurement method for receivers which are used for direct broadcasting from a satellite is proposed. By this method, G/T can be obtained without measuring G and T values separately. Therefore, this method, which can be called a direct method, can be adopted for the G/T measurement for integrated antennas, wherein an antenna and a receiver are unseparably combined, while the conventional method can not be adopted nder these circumstances. Besides,-o special test equipment is required for this method. This method can achieve more accurate G/T data because the result is independent from noise bandwidth or signal time response of test equipments. This paper describes the principle of the method, practical test procedure and some notes on how to avoid measurement errors. Some experimental results are also presented, which show that G/T values determined by this method agree with those obtained by the conventional method within 0.4 dB.     

On the use of Davidenko's method in complex root search

Davidenko's method has proved to be a powerful technique for solving a system of n-coupled nonlinear algebraic equations. It uses a Newton's method reduction to produce n-coupled first-order differential equations in a dummy variable. The advantage it offers over Newton's method and other traditional methods such as Muller's method is that it relaxes the restrictions that the initial guess has to be very close to the solution. Two examples involving the search for complex roots are presented. Davidenko's method seems to converge to the roots for all the arbitrary initial guesses considered while Muller's method appears to fail for some cases. This suggests the use of Davidenko's method as an alternative to Muller's method when the later fails to converge or is slowly convergent