基于矢量合成的相干信号干涉仪测向模型

基于通道间相位差测量的传统干涉仪测向模型在对相干多信号进行测向时会产生较大的误差,甚至测向失效,在分析其失效原因的基础上,利用相干多信号矢量合成方法,根据干涉仪基线几何结构,构建了新的相干信号干涉仪测向模型,并详细讨论了模型的求解过程。该模型不仅能够对相干多信号实施测向,而且通过对求解结果的分析可推断产生相干效应的信号个数,也能实现对传统单信号的测向,即具有较好的向下兼容性。最后通过仿真验证了模型的有效性,从而为干涉仪测向理论的发展和抗干扰应用提供了重要参考。     

CMOS电路中的闩锁效应研究

闩锁效应是功率集成电路中普遍存在的问题。文中分析了CMOS结构中的闩锁效应的起因,提取了用于分析闩锁效应的集总器件模型,给出了产生闩锁效应的必要条件,列举了闩锁效应的几种测试方法。最后,介绍了避免发生闩锁效应的几种方法。     

Structural analysis of protocol specifications and generation ofmaximal fault coverage conformance test sequences

A theoretical analysis of the fault coverage of conformance test sequences for communication protocols specified as finite state machines is presented. Faults of different types are considered, and their effect on testing is analyzed. The interaction between faults of different categories and the impact it has on conformance testing is investigated. Fault coverage is defined for the testing of both incompletely-specified machines (ISMs) and completely-specified machines (CSMs). An algorithm is presented to generate test sequences with maximal fault coverage for the testing of ISMs. It is then augmented for the testing of CSMs, and finally a technique is presented for generating test sequences which provides guaranteed maximal fault coverage for the conformance testing of communication protocols     

Synthesis of Transformer Coupled Multiple Frequency Circulators with Chebyshev Characteristics

This paper presents a theory for broad-band matching of stripline junction circulators for operation in two or more frequency bands. In this theory it is assumed that the matching network is composed of cascaded transmission line transformers each of which is an odd multiple of a quarter-wavelength at the center frequencies. The conditions for simultaneous Chebyshev response in multiple frequency bands are determined, and it is investigated to what extent these conditions can be satisfied by stripline circulator junctions. Thus by using a first-order theory, it is shown that if a circulator junction, adjusted for double frequency operation, is matched for Chebyshev response by a transformer of proper length around one of the circulation frequencies then it is also matched for Chebyshev response around the other circulation frequency, provided that the same operation mode is used above and below material resonance. A routine for broad-band multiple frequency matching is proposed for junctions where Chebyshev response is not obtainable. Finally the properties of some externally matched circulators designed according to the theories are shown.     

Universal lossless coding for sources with repeating statistics

A lower bound is derived on the achievable redundancy for universal lossless coding of parametric sources with piecewise stationary, abruptly changing, occasionally repeating statistics. In particular, it is shown that if the number of repeating statistical parameter vectors (or states) is not too large, for any uniquely decipherable code, for almost every set of states that govern all the different segments in the data sequence, for almost every arrangement of these states in the different segments, and for almost every vector of transition times, the minimum achievable redundancy is composed of 0.5 log d extra code bits for each unknown component of each state, log m extra code bits for each unknown transition time, and log s extra code bits for each repetition of a state, where d is the average duration of each state in the input string, TO is the average length of a segment, and s is the total number of states. If s is essentially large compared to TO, it is shown that the minimum redundancy is composed of 0.5 log 77i bits for each unknown component in each segment and log TO bits for each unknown transition time, which is the same lower bound as that of general piecewise stationary sources (PSSs). These results are true also in the minimax and maximin senses. The lower bound is shown to be achievable through construction of mixture and estimation based codes. Different special cases are reviewed, and it is shown that unless s is essentially large compared to m, optimal codes that are designed particularly for sources with repeating statistics outperform codes designed for PSSs when coding sources with repeating statistics. In particular, the bound for general PSSs is shown to be a special case of the new bound.     

Incremental-redundancy transmission for meteor-burst communications

The performance of type-II hybrid automatic repeat request (ARQ) is compared to that of fixed-rate type-I hybrid ARQ for meteor-burst communications. Maximum throughput is obtained for meteor-burst communications by using a transmission scheme for which the information rate of the code, varies in response to the fluctuations in the power received from a meteor trail. For type-II hybrid ARQ, a variation in the code rate is inherent in the coding scheme. On the first transmission that is made for a data block, a code of relatively high rate is used, but if an additional transmission is required, only redundant symbols are sent, and this reduces the overall rate of the code. The performance measure is the throughput per trail, which is defined as the expected number of successfully received information bits for a given meteor trail. The authors also develop an approximation for the average value of the throughput, averaged over the parameters of the meteor trail. Numerical results for Reed-Solomon codes are included to illustrate the relative performance of the various schemes. It is shown that the throughput is larger for type-II hybrid ARQ than for either fixed-rate type-I hybrid ARQ or ARQ without forward-error-correction     

Programmed instruction and computer-assisted instruction—An overview

An overview of Programmed Instruction (PI) is presented and its philosophy described. A brief delineation of courses in programmed format for the training of computer programmers and computer maintainers is given. The extent of programmed instruction activity for educating engineers in preparation for assignments is discussed. Computer-Assisted Instruction (CAI) is defined, and the bridge between CAI and PI is examined. Attention is given to current research in CAI and to the roles of the learner, teacher, instructional programmer, and computer programmer. A major conclusion reached is that there exists a growing need for the development of instructional programmers and for the production of more adequate computer software. Finally, attention is given to the development of software and hardware for CAI systems. Specifications for a typical CAI language and system are presented, and the authors reflect upon future CAI systems.     

On the Performance of a Two-User MIMO Downlink System in Heavy Traffic

A multiple-input multiple-output (MIMO) downlink system in which data is transmitted to two users over a common wireless channel is considered. The channel is assumed to be fixed for all transmissions over the period of interest and the ratio of anticipated average arrival rates for the two users, also known as the relative traffic rate, is the system design parameter. A packet-based traffic model is considered where data for each user is queued at the transmit end. A queueing analog for this system leads to a coupled queueing system for which a simple policy is known to be throughput-optimal under Markovian assumptions. Since an exact expression for the performance is not available, as a measure of performance (in heavy traffic), a diffusion approximation is established. This diffusion process is a two-dimensional (2-D) Semimartingale Reflecting Brownian Motion (SRBM) living in the positive quadrant of 2-D space     

16DAPSK+OFDM及其在数字调幅广播中应用

本文提出一种新的频域16DAPSK＋OFDM。并讨论它的频域差分调制和解调,然后在白高斯信道分析它的误比特性能。同时域16DASK＋OFDM相比,频域16DAPSK＋OFDM可用于信道特性随时间变化更快的应用。最后,在典型的调幅（AM）波段信道对两者误比特性能进行了仿真。结果表明,时域和频域16DPSK＋OFDM都可用于中短波信道。在中波信道,时域16DAPSK比例域16DAPSK性能要好,在短波信道,频域16DAPSK比时域16DAPSK性能要好。另外,两者调制和解调的计算复杂度基本一样,且都不需要信息道均衡。     

Dynamic programming solution for a class of pursuit evasionproblems: the herding problem

A herding dog and sheep problem is studied where the agent “dog” is considered the control action for moving the agent “sheep” to a fixed location using the dynamics of their interaction. The problem is solved for the deterministic case using dynamic programming. Proofs are provided for the correctness of the algorithms. The algorithm is analyzed for its complexity. A software package developed for experimentation is described     

Zoom-FFT的改进、频谱反演与时-频局部化特性

回顾了经典连续分段序列Zoom-FFT方法.定义了时间分段序列的占空比 R _ms.分析了在实际应用中对 R _ms＜1的时间分段序列的Zoom-FFT处理的需求并建立了处理这种序列的新方法.提出并证明了 R _ms为任意值的Zoom-FFT频谱反演回实际频谱的理论公式和修正公式.给出了对跳频信号进行 R _ms=1的Zoom-FFT处理和对话带信号进行 R _ms＜1的Zoom-FFT处理并反演回实际频谱的例子.证明Zoom-FFT方法对解决信号快速搜索和粗分析与信号细节分析的矛盾有实用价值,间断分段序列的Zoom-FFT进一步提高了分析效率.最后讨论了Zoom-FFT具有类似于小波变换的时-频局部化特性问题.     

基于SISE方程的广义gamma分布参数估计方法

广义gamma分布是近年来用于SAR图像统计建模重要分布之一,参数估计是制约其应用的核心问题。该文提出了一种新的参数估计方法。首先分析了的对数累积量参数估计方法(Mehtod-of- Log-Culmulants, MoLC)的不足,接着推导了基于SISE (Scale-Independent-Shape-Estimation)方程的参数估计表达式,并给出了具体的求解方法。最后,利用蒙特卡洛仿真的实验结果表明,该文方法稳定性和有效性优于MoLC。     

Japanese radar development prior to 1945

Early work on magnetrons and on radar for the Japanese Navy is summarized. The development, during World War II, of microwave radars for various warships and for land-based use, is discussed. Research on super-high-power-output magnetrons for shooting down aircraft is described. Radar for the Japanese army is also described     

卫星信号模拟器中多普勒频移模拟的研究

文章分析了动态环境下多普勒频移的产生,研究了多普勒频移的估算方法并建立了数学模型,在此基础上提出了一种运用DSP结合专用的DDS芯片AD9954模拟多普勒频移的方案。并根据所模拟数据的要求选择了一种可行AD9954的工作模式,介绍了参数的计算方法,给出了DSP控制AD9954进行多普勒频移模拟的程序流程。     

An efficient heuristic for standard-cell placement

A new method is presented for optimization of the one and two-dimensional quadratic assignment problem. The method is suitable for placement problems as they appear in sea-of-gates and standard-cell layout styles for VLSI design. The method is based on recursive partitioning and is a generalization of the method introduced by Kuh et al. It is more flexible than Kuh's method because it does not require a special distribution of the external connections on the boundary of the chip. The time complexity of the algorithm is O(_n Iog²_n). A numerical evaluation of the method is presented, which shows its efficiency for generating near optimal solutions for the quadratic assignment problem as well as for practical standard-cell placement problems.     

考虑电子注与场自洽互作用的奥罗管的大信号分析

本文仅对于简化模型探讨了关于奥罗管(orotron)的效率(起振问题),导出了影响效率的重要参量Zc,给出了关于这种器件的电子注与场互作用的大信号自洽解,并举例对实际参量进行了数值计算。计算结果指出,为了保证奥罗管能在宽频范围内调谐的前提下研制实用的器件,在设计准光腔的时候,不仅应追求高的品质因数,还应使与电子注作用的光栅上的模斑尽还能伸长和展宽,对于所采用的紧贴光栅表面掠过的电子注,应尽可能提高其电流值。     

Multispectral bathymetry using a simple physically based algorithm

A simple method for estimating water depths from multispectral imagery is described and is applied to several IKONOS data sets for which independent measurements of the water depth are available. The methodology is based on a physical model for the shallow-water reflectance, and is capable of correcting for at least some range of water-quality and bottom-reflectance variations. Corrections for sun-glint effects are applied prior to the application of the bathymetry algorithm. The accuracy of the depth algorithm is determined by comparison with ground-truth measurements, and comparisons between the observed and calculated radiances are presented for one case to illustrate how the algorithm corrects for water-attenuation and/or bottom-reflectance variations.     

Adjustable speed control of ultrasonic motors by adaptive control

The driving principle of the ultrasonic motor (USM) is different from those of the electro-magnetic type motors. Some mathematical models for the USM have been reported; however, these models are very complex to apply for speed control of the USM. Therefore, the speed controllers have been designed using PI controllers or fuzzy controllers and it is necessary to develop a simple and convenient mathematical model for the USM in order to achieve a high-performance speed control. In this paper, a mathematical model for the USM is proposed which is simple and useful for speed control. The speed controller is designed based on the model using adaptive control theory. Adaptive control is attractive for control of the USM because the speed characteristics of the USM vary with drive conditions. The application of this control scheme to speed control for the USM is attempted first. The effectiveness of proposed control is demonstrated by experimental     

Temperature control for food in pots on cooking hobs

A control system for the temperature of food in a cooking pot is introduced. The cooking pot is heated on a consumer cooking hob. The temperature of the pot side is used as input for the controller. It is measured by an infrared detector. The infrared detector is a thermopile. The sensor signal is evaluated by a rule-based control algorithm. The system is simple, reliable, and very user friendly. An exact temperature settlement in a consumer hob is available for the first time. The system is used for automatic cooking     

远程空空导弹发射问题的研究

在导弹发射技术上,远程空空导弹明显不同于中、近程空空导弹。为解决远程空空导弹的发射问题,文章提出了一种远程空空导弹攻击区的确定方法,建立了估计导弹对目标预测拦截时间的算法,讨论了发射远程空空导弹的信息需求及获取方法,并基于以上研究拟订了发射远程空空导弹的火控算法。最后给定目标随机参数的变化范围,对远程空战过程进行了仿真。大量仿真结果表明,可靠发射、非完全可靠发射和非完全可靠强化发射条件下有不同的成功概率,这种发射条件的火控算法从理论上有效地解决了远程空空导弹的发射问题。