Acknowledgment for 1973 paper on multiplexed communication channels

A new method of apodizing single metallization interdigital transducers is presented. For each new apodizing function, only a new simple apodizing mask is required. The method involves no critical alignment. Dummy electrodes are inherently provided.     

A novel method of temperature compensation for multiplexed liquid crystal displays

A new, simple technique for compensating the drive voltages to allow for temperature changes of multiplexed liquid crystal displays is described. No components apart from the display and drive electronics are required and compensation over the temperature range 0°C to 50°C has been achieved.     

光折变晶体中多重全息图分批定影热固定的研究

首次描述了多重全息图分批定影热固定的记录－补偿－多次光擦除及平滑－显影的存储固定机制,并据此对分批存储定影过程中的全息电子光栅和离子光栅的行为进行了详细理论分析。研究结果表明,多次光擦除平滑阶段中获陷电子对离子光栅的屏蔽作用所引起的光擦除减缓效应,是分批定影热固定法能够有效提高多重全息图固定后衍射效率的根本原因。     

A new method for calculation of majority carrier compensation in photovoltaics Zhang Rumin(张汝民)1,2*,Liu Dijun(刘迪军)2,3, Su Guobin(苏国斌)3

在对薄膜太阳能电池的研究中,半导体材料通常包含多个杂质/缺陷态的施主和受主掺杂剂。根据局部电中性（LCN）条件,可以确定平衡费米（EF）水平及电子和空穴浓度。但是LCN方程是一个超越方程,不可能得到它的解析解,只能使用图形或数值方法求解。因此,研究者Chin提出了一种可用于多施主和受主半导体的多数载流子补偿估计的简单近似图解法（GM）。通过引入掺杂排位的概念和阶跃函数,近似的浓度和费米能级变得很容易得到。本文分析的图解法,提出了一种新的数值与图形的方法（NGM）,并对NGM与GM计算精度进行了仿真验证。通过数值计算的引入,GM方法的应用进一步得到了扩展。     

一种MIMO-OFDM信道混合估计方法

传统的信道估计方法往往假设多径分量数已知且为常数,粒子滤波算法可估计服从高斯分布的时变信道。实际无线环境中,多径分量数目与幅度皆为时变,则粒子滤波估计方法性能恶化。本文提出基于二进制粒子群算法和卡尔曼滤波的MIMO-OFDM信道混合估计方法。采用随机集建模MIMO信道,并分析得到其多径转移概率模型;基于此模型将信道分解为离散部分和连续部分,推导得到此两部分与整体信道关系;采用二进制粒子群算法拟合信道离散部分,利用卡尔曼滤波估计信道幅度,将利用信道估计计算得到的观测值与真实观测值的近似程度作为适应度函数。仿真结果表明:本文所提出的信道估计方法性能优于基本粒子滤波的信道估计方法。     

A novel method for increasing the spectral efficiency of optical CDMA

Given K simultaneously active users, an Optical CDMA (OCDMA) receiver needs to discriminate among K codes. Since the number of available codes C is always C >> K at any given time for any truly asynchronous OCDMA system that employs quasi-orthogonal codes, there is always a set of unused codes. We here propose to exploit these unused codes to increase the spectral efficiency of the system. This can be accomplished by exclusively assigning to each user a set of M codes which represent a log/sub 2/(M)-tuple of bits so that each user effectively uses a multi-dimensional modulation (multiple information bits per code are conveyed). In this paper, we analyze the performance of such a system and find in closed form an upper bound on the average probability of error. Moreover, we report for the first time that, under lightly loaded, non interference-limited conditions, the multi-dimensional OCDMA scheme here proposed allows us to obtain both higher spectral efficiency and lower biterror probability (BEP) than a conventional OCDMA system, which employs one code only per user. The analysis here presented allow us to formulate a useful system design criterion that yields truly asynchronous OCDMA systems with very high spectral efficiency.     

General strategy for increasing type number of control systems

A new method is developed for increasing the type number of a control system by means of input processing. Several examples are given, one of them designed to illustrate the application of the standard forms derived by Graham and Lathrop.     

A method for comparison of pseudo-random number generators

In this paper a method for comparison of pseudo-random number generators which have uniform distributions in the interval [0, 1] is proposed. With the suggested criterion, it is better to use a pseudo-random number generator whose distribution of the pseudo-random variable is closer to the ideal uniform distribution. The application of the suggested method is illustrated by an example.     

A practical method for approaching the channel capacity ofconstrained channels

A new coding technique is proposed that translates user information into a constrained sequence using very long codewords. Huge error propagation resulting from the use of long codewords is avoided by reversing the conventional hierarchy of the error control code and the constrained code. The new technique is exemplified by focusing on (d, k)-constrained codes. A storage-effective enumerative encoding scheme is proposed for translating user data into long dk sequences and vice versa. For dk runlength-limited codes, estimates are given of the relationship between coding efficiency versus encoder and decoder complexity. We show that for most common d, k values, a code rate of less than 0.5% below channel capacity can be obtained by using hardware mainly consisting of a ROM lookup table of size 1 kbyte. For selected values of d and k, the size of the lookup table is much smaller. The paper is concluded by an illustrative numerical example of a rate 256/466, (d=2, k=15) code, which provides a serviceable 10% increase in rate with respect to its traditional rate 1/2, (2, 7) counterpart     

A method for increasing the dynamic performance of pneumatic servosystems with digital valves

Pneumatic servosystems realised with digital valves piloted using modulation techniques suitable for regulating airflow have numerous advantages in terms of economy, reliability and simplicity of installation and use. On the downside, an important technological limit is set by the need to use valves with very low response times and consequently small sizes. This limitation can even make it difficult to obtain satisfactory dynamic performance in servosystems characterised by the presence of large chambers. To avoid having to use to high a number a digital valves, which can be the cause of excessive costs and risks of failure, it is possible to hypothesise the use alongside small fast valves of valves of greater size, characterised by response times of 10/20 ms, which can be used to handle high flows when necessary. The creation of a servosystem of this kind requires the development of a precise control strategy which makes it possible to guarantee both the precision of the controller and the speed of response simultaneously.

This paper develops some considerations aimed at defining criteria for selecting valves and the experimental results obtained in the case study of an application involving the pressure control of a tank.     

一种时变信道条件下OFDM系统的信道估计方法

针对正交频分复用（OFDM）系统，本文提出了一种时变条件下的信道估计方法。文中假设数据以包为单位进行传输，导频序列以叠加的方式和数据序列相结合，在得到对应于数据包内每帧OFDM信号的信道冲激响应之后，再在一个包内对这些信道冲激响应进行加权平均，从而提高信道估计的精度。     

A moment-based blind method for identification of FIR down-linkDS-CDMA channels

In order to achieve lower bit error rates (BERs), multiuser detection techniques have been proposed. Generally, multiuser detectors can provide excellent performance only when channel parameters are precisely known. In this paper, we propose a moment-based blind method to estimate down-link channels precisely. The mean square error (MSE) expression of the channel vector estimate has been derived. Through simulations, we show the effect of the channel estimation error on the performance of a multiuser detector. In this paper, we also show that finite impulse response (FIR) channels can be blindly identified by using the proposed method and the spreading operation. Since the spreading operation of the code division multiple access (CDMA) can induce cyclostationarity, any FIR channel can be identified by the proposed method. Of course, in order to guarantee identifiability, some conditions on the spreading codes will be satisfied. In this paper, these conditions are also found     

A method for evaluation of number class intervals of histogram

An approximate formula is proposed for evaluation of number class intervals of a histogram. The results obtained by applying this formula are compared with those obtained by using well-known formulae. The comparisons show that the suggested formula, in many cases, gives more acceptable results. This is illustrated by an example.     

A parametric method for determining the number of signals innarrow-band direction finding

A novel and more accurate method to determine the number of signals in the multisource direction finding problem is developed. The information-theoretic criteria of Y. Yin and P. Krishnaiah (1988) are applied to a set of quantities which are evaluated from the log-likelihood function. Based on proven asymptotic properties of the maximum likelihood estimation, these quantities have the properties required by the criteria. Since the information-theoretic criteria use these quantities instead of the eigenvalues of the estimated correlation matrix, this approach possesses the advantage of not requiring a subjective threshold, and also provides higher performance than when eigenvalues are used. Simulation results are presented and compared to those obtained from the nonparametric method given by H. Wax and T. Kailath (1985)     

A method for increasing the accuracy of measuring the radar cross section of low-reflection objects

A method and technical recommendations for lowering the influence of the main components of the measurement error on the accuracy of measuring the radar cross section of low-reflection objects on a radar measuring complex of open type are proposed.     

任意通道数超分辨测向算法

提出了一种可适用于任意通道数的超分辨测向算法.通过多路开关切换实现对协方差矩阵的测量,进而重新构造了天线阵列导向矢量,实现超分辨测向.当前的算法只能用于通道数等于1或天线阵元数的情况,新算法突破了该限制,拓展了超分辨测向算法的适用范围.对算法进行了详细的理论推导.计算机仿真结果表明该算法性能优于单通道算法,接近经典测向算法.     

A holographic (synthetic aperture) method for increasing the gain of ground-to-air radars

The usual synthetic aperture radar operates from a moving aircraft and achieves the effect of a very long synthetic antenna with its accompanying high gain and resolution. This letter suggests the application of the same concept to a ground-to-air radar, whereby a small ground-based transmit-receive antenna would effectively be provided with a large synthetic gain against nearby planes flying at uniform speeds.     

一种提高椭圆聚光腔面轮廓度精度的加工方法

本文介绍了一种提高椭圆聚光腔面轮廓度精度的加工方法,用这种方法加工的椭圆聚光腔的面轮廓度精度达到0.02mm.     

A general method for calculating error probabilities over fading channels

Signal fading is a ubiquitous problem in mobile and wireless communications. In digital systems, fading results in bit errors, and evaluating the average error rate under fairly general fading models and multichannel reception is often required. Predominantly to date, most researchers perform the averaging using the probability density function method or the moment generating function (MGF) method. This paper presents a third method, called the characteristic function (CHF) method, for calculating the average error rates and outage performance of a broad class of coherent, differentially coherent, and noncoherent communication systems, with or without diversity reception, in a myriad of fading environments. Unlike the MGF technique, the proposed CHF method (based on Parseval's theorem) enables us to unify the average error-rate analysis of different modulation formats and all commonly used predetection diversity techniques (i.e., maximal-ratio combining, equal-gain combining, selection diversity, and switched diversity) within a single common framework. The CHF method also lends itself to the averaging of the conditional error probability involving the complementary incomplete Gamma function and the confluent hypergeometric function over fading amplitudes, which heretofore resisted to a simple form. As an aside, we show some previous results as special cases of our unified framework.