The Feature of DDR SDRAM and the Implementation of DDR SDRAM Controllers via VHDL

1　ＩｎｔｒｏｄｕｃｔｉｏｎＮｏｗａｄａｙｓ,ｓｔｏｒａｇｅｔｅｃｈｎｏｌｏｇｙｈａｓｄｅｖｅｌｏｐｅｄｆａｓｔａｃｃｏｒｄｉｎｇｔｏｔｈｅｄｅｍａｎｄｏｆｄｉｆｆｅｒｅｎｔａｐｐｌｉｃａ ｔｉｏｎｓ .ＷｅｈａｖｅｈａｄＤｙｎａｍｉｃＲＡＭ (ＤＲＡＭ )ａｎｄＳｔａｔｉｃＲＡＭ (ＳＲＡＭ ) ,ＢｂｕｒｓｔＥｘｔｅｎｄｅｄＤａｔａＯｕｔ ｐｕｔＲＡＭ (ＢＥＤＯＲＡＭ ) ,ＳｙｎｃｈｒｏｎｏｕｓＤＲＡＭ(ＳＤＲＡＭ)ａｎｄＲａｍｂｕｓＤＲＡＭ(ＲＤＲＡＭ)ＮｏｗｗｅｈａｖｅａｌｓｏｈａｄＤｏｕｂｌｅＤａｔａＲａｔ…     

A New Optical Fiber Loop System Used in Measurement of Dispersion Compensation Ability

ＡＮｅｗＯｐｔｉｃａｌＦｉｂｅｒＬｏｏｐＳｙｓｔｅｍＵｓｅｄｉｎＭｅａｓｕｒｅｍｅｎｔｏｆＤｉｓｐｅｒｓｉｏｎＣｏｍｐｅｎｓａｔｉｏｎＡｂｉｌｉｔｙＭａｎｕｓｃｒｉｐｔｒｅｃｅｉｖｅｄＤｅｃ．２４，１９９６．ＳｕｐｐｏｒｔｅｄｂｙＫｅｙＰｒｏｊｅｃｔ...     

电子缩略新语卡(8)

Ｂ－ＩＳＤＮ　Ｂｒｏａｄｂａｎｄ　ＩＳＤＮ　宽带综合业务数字网Ｂ－ＭＡＣ　Ｂｒｏａｄｃａｓｔｉｎｇ　Ｍｕｌｔｉｐｌｅｘｅｄ　ａｎａｌｏｇ　Ｃｏｍｐｏｎｅｎｔ　（卫星图像传输方法）广播复用模拟部件Ｂ－ＳＲＡＭ　Ｂｕｒｓｔ　ＳＲＡＭ　突发方式同步型高速ＳＲＡＭＢＡＣＰ　ＢＡｎｄ　Ａｌｌｏｃａｔｉｏｎ　Ｃｏｎｔｒｏｌ　Ｐｒｏｔｏｃｏｌ（传输速度自动调节）频带配置控制协议ＢＡＴ　Ｂｅｓｔ　Ａｖａｉｌａｂｅ　Ｔｅｃｈｎｏｌｏｇｙ最佳可利用技术ＢＢ　Ｂａｓｅ　Ｂａｎｄ基带ＢＢ　Ｂｏｏｋ　ｔｏ　Ｂｉｌｌ　ｒ…     

INDEX TO VOLUME23(2001)

ＳｕｂｊｅｃｔＭａｔｔｅｒＡｕｔｈｏｒＮｏ .ＰａｇｅＳＵＲＶＥＹ＆ＲＥＶＩＥＷＴｈｅＳｃａｎｎｉｎｇａｎｄＳｔａｒｒｉｎｇＦＰＡｉｎＩｎｆｒａｒｅｄＳｙｓｔｅｍｓＣＡＩＹｉ 13ＮｅｗＡｄｖａｎｃｅｏｆＩＲＭＡＷＳａｔＡｂｒｏａｄＦＵＷｅｉ,ＨＯＵＺｈｅｎ ｎｉｎｇ 3 1ＴｈｅＲｅｃｅｎｔＰｒｏｇｒｅｓｓｏｆＳｕｂｍｉｌｌｉｍｅｔｅｒＷａｖｅＴｅｃｈｎｏｌｏｇｙＺＨＡＮＧＸｕｎ ,ＺＨＡＮＧＰｉｎｇ ,ＬＩＨｏｎｇ ｊｉａｎ ,ｅｔａｌ. 3 4ＡｎＡｎａｌｙｓｉｓＩＲＤｅｔｅｃｔｉｎｇａｎｄＴｒａｃｋｉｎｇ…     

Technique of Position Sensitive Detector with Alternating Light Source

ＴｅｃｈｎｉｑｕｅｏｆＰｏｓｉｔｉｏｎＳｅｎｓｉｔｉｖｅＤｅｔｅｃｔｏｒｗｉｔｈＡｌｔｅｒｎａｔｉｎｇＬｉｇｈｔＳｏｕｒｃｅ①ＳＵＭｅｉｊｕｎ（ＨｅｆｅｉＵｎｉｖｅｒｓｉｔｙｏｆＴｅｃｈｎｏｌｏｇｙ，Ｈｅｆｅｉ２３０００９，ＣＨＮ）Ａｂｓｔｒａｃｔ：...     

Universal Spectral Modulation Sensors:(Ⅰ)Theory and Structure

ＵｎｉｖｅｒｓａｌＳｐｅｃｔｒａｌＭｏｄｕｌａｔｉｏｎＳｅｎｓｏｒｓ：（Ⅰ）ＴｈｅｏｒｙａｎｄＳｔｒｕｃｔｕｒｅ①ＳＨＩＹｏｎｇｊｉ（ＬｕｏｙａｎｇＴｅｃｈｎｏｌｏｇｙＣｏｌｅｇｅ，Ｌｕｏｙａｎｇ４７１００３，ＣＨＮ）Ａｂｓｔｒａｃｔ：Ａｕｎｉｖｅｒ...     

SEM and Positron Annihilation Technology Investigation on the Defect Change with Thermal Treatment Temperature in GaP

ＳＥＭａｎｄＰｏｓｉｔｒｏｎＡｎｎｉｈｉｌａｔｉｏｎＴｅｃｈｎｏｌｏｇｙＩｎｖｅｓｔｉｇａｔｉｏｎｏｎｔｈｅＤｅｆｅｃｔＣｈａｎｇｅｗｉｔｈＴｈｅｒｍａｌＴｒｅａｔｍｅｎｔＴｅｍｐｅｒａｔｕｒｅｉｎＧａＰ①②ＺＨＡＮＧＦｕｊｉａ，ＳＨＡＯＪｉａｆｅｎ...     

VLSI Structure for an All Digital Receiver for CDMA PABX Handset

ＶＬＳＩＳｔｒｕｃｔｕｒｅｆｏｒａｎＡｌｌＤｉｇｉｔａｌＲｅｃｅｉｖｅｒｆｏｒＣＤＭＡＰＡＢＸＨａｎｄｓｅｔＺｈｏｕＳｈｉｄｏｎｇ；ＢｉＧｕａｎｇｇｕｏ（ＳｏｕｔｈｅａｓｔＵｎｉｖｅｒｓｉｔｙ，Ｎａｎｊｉｎｇ２１００１８）（Ｐｈ．Ｄｓｔｕｄｅｎｔａｔ...     

A Method for 3D Scene Description and Segmentation in an Object Record

ＡＭｅｔｈｏｄｆｏｒ３ＤＳｃｅｎｅＤｅｓｃｒｉｐｔｉｏｎａｎｄＳｅｇｍｅｎｔａｔｉｏｎｉｎａｎＯｂｊｅｃｔＲｅｃｏｒｄ￥ＣｈｅｎＴｉｎｇｂｉａｏ（ＤｅｐａｒｔｍｅｎｔｏｆＲａｄｉｏＥｎｇｉｎｅｅｒｉｎｇ，ＮａｍｉｎｇＵｎｉｖｅｒｓｉｔｙｏｆＰｏｓｔｓ...     

Convergence Rate Evaluation of a DS-CDMA System with Centralized Power Control By Genetic Algorithm

1　ＩｎｔｒｏｄｕｃｔｉｏｎＲｅｃｅｎｔｌｙ ,ＤｉｒｅｃｔＳｅｑｕｅｎｃｅｓｐｒｅａｄＣｏｄｅＤｉｖｉｓｉｏｎＭｕｌｔｉｐｌｅＡｃｃｅｓｓ (ＤＳ ＣＤＭＡ)ｈａｓｂｅｃｏｍｅａｌｅａｄｉｎｇｍｕｌｔｉｐｌｅａｃｃｅｓｓｔｅｃｈｎｏｌｏｇｙｆｏｒｃｅｌｌｕｌａｒｗｉｒｅｌｅｓｓｓｙｓ ｔｅｍｓ,ｉｎｗｈｉｃｈｔｈｅｒｅｈａｖｅｂｅｅｎｓｉｇｎｉｆｉｃａｎｔｃｈｉｅｖｅ ｍｅｎｔｓ.Ｉｎｔｈｅｌｉｔｅｒａｔｕｒｅ ,ｔｈｅｒｅｈａｖｅｂｅｅｎｒｅｓｅａｒｃｈｅｓｏｎｐｏｗｅｒｃｏｎｔｒｏｌａｌｇｏｒｉｔｈｍ…     

Performance of Noncoherent Direct-Sequence Spread-Spectrum Multiple-Access Communications

The performance of noncoherent reception in direct-sequence spread-spectrum multiple-access communications systems is investigated for additive white Gaussian noise channels. Analytical and numerical results on the probability of error are presented for binary andM-ary frequency-shift-keying data modulation with noncoherent demodulation and differential-phase-shift-keying data modulation with differentiallycoherent demodulation. Both synchronous and asynchronous systems are analyzed. Systems which employ deterministic as well as random signature sequences are considered. The multiple access capability of noncoherent DS/SS systems is evaluated and compared to that of coherent DS/SS systems with the same parameters. The comparison shows that the loss in the performance of DS/SSMA systems due to noncoherent reception can be considerably larger than the loss incurred to noncoberent single-user systems operating in additive Gaussian noise.     

Chip‐interleaving direct sequence spread spectrum system over Rician multipath fading channels

Chip interleaving (CI) is a unique technique to exploit time diversity in direct sequence spread spectrum (DS/SS)‐based systems operating in fading environments. In order to facilitate design of CI systems in various fading situations, we present a performance analysis for CI DS/SS system over Rician multipath time‐varying fading channels. We derive the analytical bit error rate (BER) expression for CI DS/SS to allow fast and accurate evaluation of BER performance based on the interleaving depth selected, spreading codes employed, and the time correlation function of the channel. We then discuss some ideal cases by using the analytical results to reveal some of the insights presented in the performance analysis. For the purpose of comparison, we also obtain the BER expression for conventional DS/SS system as a special case of CI system with an interleaving depth of one. Using numerical examples, we verify the analytical results with computer simulations and illustrate the BER performance behavior of CI DS/SS system with varying interleaving depth for all possible combinations of two sets of spreading codes of different type and two different time correlation functions of the channel. Copyright © 2011 John Wiley & Sons, Ltd.     

一种网格编码高维直扩通信方式的研究

本文首先提出高维直扩通信系统的概念,定义决定系统基本形态的“中介码”．高维直扩系统比现有的几种多进制直扩系统更一般化,可为构造更有效的直扩通信方式拓宽思路．为了减小多址干扰和远近效应提出一种网格编码高维直扩通信方式,并给出在多址环境下系统渐近差错性能的数值结果．最后给出对全文的总结和提出尚待研究的问题．     

自适应滤波在扩频信号分集接收中的应用研究

使用自适应滤波器完成对扩频信号的扩频码捕获后,传输信道中由于信号衰落造成的多径信号的幅度就可以从自适应滤波器收敛后的系数权值向量上体现出来.根据分集接收的理论分析,依据多径信号的信号幅度值进行分集接收在理论上是可行的,因此利用自适应滤波器对接收到的多径信号进行隐分集接收是完全可行的.使用自适应滤波器在完成扩频码捕获的同时,在不增加额外硬件支路的情况下就可以实现对多径信号的分集接收功能,从而改善在多径衰落环境下的信道传输性能.     

A digital chip timing recovery loop for band-limiteddirect-sequence spread-spectrum signals

Migration towards a full-digital implementation of modems is currently one of the main trends in transmission systems design. The authors describe a noncoherent all-digital delay lock loop (DDLL) suited for chip timing synchronization in band-limited direct sequence spread spectrum (DS/SS) systems, and they thoroughly analyze its performance. The key features of this novel scheme are represented by its low-complexity processing section together with its good tracking capability. Analytical expressions for the DDLL S-curve and steady-state timing jitter are derived and confirmed by a time-domain computer simulation. Furthermore, the Mean Time to Lose Lock (MTLL) of the loop is evaluated and some numerical results are reported. The proposed chip timing synchronization scheme reveals also an improved tracking performance when compared to the traditional analog DLL for rectangular chip DS/SS signals     

Performance analysis of forward link beamforming techniques forDS/CDMA systems using base station antenna arrays

The performance of DS/CDMA systems using forward link beamforming and RAKE diversity combining is investigated analytically in frequency selective fading channels, whereas previous studies have resorted to Monte Carlo simulations in flat fading channels. The capacity of DS/CDMA systems is considerably improved by employing forward link beamforming     

Detection performance of chaotic spreading LPI waveforms

Low probability of intercept (LPI) performance of a direct-sequence (DS) spread-spectrum (SS) system with chaotic spreading sequences is investigated in this paper. Several intercept receivers, including energy detectors, synchronous and asynchronous, coherent and noncoherent structures, which are typically used to detect binary DS SS signals, are examined here to detect the presence of chaotic DS SS signals. A simple detection approach using a binary correlating function to detect nonbinary chaotic sequences is proposed. The expressions of detection probabilities of chaotic spreading signals using those intercept receivers are derived. Comparisons between systems using chaotic and binary sequences are given in terms of the LPI performance, and the performance improvement with chaotic spreading sequences is observed.     

Acquisition of PN code with adaptive threshold for DS/SScommunications

An adaptive acquisition scheme of PN sequences is presented for DS/SS communications. The basic idea of the scheme is to apply the radar CFAR technique to the acquisition of PN sequences. The detection performance is analysed and an example of adaptive thresholding for multipath Rayleigh fading channels is given     

Code acquisition of DS/SS signals in fading channels using an LMSadaptive filter

The mean acquisition time performance for a direct-sequence spread-spectrum (DS/SS) code acquisition technique utilizing a finite impulse response (FIR) least-mean-square (LMS)-adaptive filter is investigated in fading conditions. The optimum tap-weight vector for the adaptive filter is derived and computer simulation results are presented to assess the acquisition performance for the system. It is shown that fading causes a slight degradation to the mean acquisition time (less than 3-dB signal-to-noise ratio (SNR) degradation) which is far less than that incurred by other systems utilizing matched filters (about 10 dB). In frequency selective fading channels, the adaptive nature of the proposed scheme is exploited to acquire the strongest received path and as the paths fade the new strongest available path is acquired     

Performance analysis of a hybrid DS/SFH CDMA system usinganalytical and measured pico cellular channels

This paper presents the throughput and delay analysis of a packet-switched code division multiple access (CDMA) network based on the hybrid direct sequence (DS)/slow frequency hopping (SFH) spread-spectrum multiple access (SS MA) technique with Q-, B-, and D-PSK modulation using analytical and measured pico cellular channels. The performance of the hybrid DS/SFH, DS, and SFH multiple access techniques have been compared in a pico cellular personal communications network (PCN) environment. Multipath and multiple access interference are considered. The performance is evaluated for a given delay spread and a fixed bandwidth. The effects of forward error correction (FEC) coding and diversity techniques, such as selection diversity and maximal ratio combining on the performance, are also investigated