NEC为1G DRAM开发最小的存储单元

ＮＥＣ为１ＧＤＲＡＭ开发最小的存储单元日本ＮＥＣ公司已为１ＧｂＤＲＡＭ开发了世界上最小的ＤＲＡＭ存储单元─０．３７５μｍ２。这种单元与在ＩＳＳＣＣ９５＇上宣布的用在１ＧｂＤＲＡＭ样品的单元有所不同，这种０．３７５μｍ２的单元技术包括对角开位线结构，相...     

MC68HC05CD总线结构设计

无ＲＯＭ扩展总线微控制器ＭＣ６８ＭＣ０５ＣＤ具有板上并行输入／输出（Ｉ／Ｏ）、两个定时器、串行通信接口（ＳＣＩ）和ＲＡＭ，而仅仅缺少ＥＰＲＯＭ。总线结构是设计微控制器系统时的最重要的考虑之一。图１ＭＣ６８ＨＣ０５Ｃ０片选、存储器图和三个不同大小外部Ｅ...     

综合业务CDMA系统在不同无线环境下的容量分析

个人通信和移动计算的发展促进了将综合业务引入移动通信中。ＣＡＭＡ系统是适合于传输综合业务的系统。本文首先给出了一种业务接入控制算法，并在此算法下，对综合业务的ＣＤＭＡ系统的容量做一简要分析。为满足不同业务的ＱｏＳ（Ｑｕａｌｉｔｙ ｏｆ Ｓｅｒｖｉｃｅ）要求，对于不同的业务在传输时给予不同的功率。为克服速率较高的业务需要较大的功率的问题，对速率较高的业务给予较宽的传输带宽。不同的业务在同一频段中传输     

新品展馆

０．１７μｍ ＤＲＡＭ批量生产 三星电子设备有限公司准备批量生产第三代Ｒａｍｂｕｓ动态随机存取存储器芯片（ＲＤＲＡＭ）。ＲＤＲＡＭ使用０．１７μｍ设计规则，其电路尺寸仅为人发截面的１／６００。该公司生产的这种ＲＤＲＡＭ存储器容量有１２８Ｍｂ、１４４Ｍｂ和２８８Ｍｂ三种。安装在一个单一系统上的４块２８８Ｍｂ组件支持的存储器容量可高达２Ｇｂ。第三代０．１７μｍ设计规则的应用意味着在一块晶片上安装的芯片数要比采用第二代技术生产的多２５％。三星公司的下一代批量生产技术将使芯片尺寸缩小，并将缩短芯片内部信号…     

NEC、日立在ISSCC上发表1GDRAM

ＮＥＣ、日立在ＩＳＳＣＣ上发表１ＧＤＲＡＭ据ＩＳＳＣＣ’９５的发表内容，ＮＥＣ、日立已经在世界上率先开发了１ＧＤＲＡＭ。ＮＥＣ开发的１ＧＤＲＡＭ的特点是，采用０．２μｍ电子束曝光技术和钽氧化膜低温（５００℃）工艺技术以０．２５μｍＣＭＯＳ工艺，存贮单...     

IDR与DCME技术在卫星通信中的应用

近年来，数字通信、程控交换和ＩＳＤＮ迅速发展，但在ＩＮＴＥＬＳＡＴ的业务中，模拟ＦＤＭ／ＦＭ载波还占一定比例，为了使卫星传输链路数字化，ＩＮＴＥＬＳＡＴ通过收费的优惠政策，鼓励卫星用户使用ＩＤＲ／ＤＣＭＥ来替代ＦＤＭ／ＦＭ载波。ＩＤＲ载波可传数字化信息，它与ＦＤＭ／ＦＭ载波一样，以ＦＤＭＡ方式工作。它属于ＴＤＭ／ＱＰＳＫ／ＦＤＭＡ制式，目前工作于ＦＤＭ／ＦＭ制式的地球站只需将ＦＤＭ／ＦＭ终端改为ＩＤＲ终端，更换上／下变频器的本振，降低相位噪声，使其符合ＩＤＲ的相位噪声要求，就能把模拟的ＦＤＭ／ＦＭ业务改造成ＩＤＲ业务。     

MC68HC05SR3芯片介绍

ＭＣ６８ＨＣ０５ＳＲ３芯片介绍黄小平一、基本结构及特征ＭＣ６８ＨＣ０５ＳＲ３ＨＯＭＯＳ微控制器是低功耗单片微控制器Ｍ６８ＨＣ０５家族的一员。这个Ｓ位的微控制器单元（ＭＣＵ）包含有在片振荡器，ＣＵＰ、ＲＡＭＥＯＭ、Ｉ／Ｏ，定时器及Ａ／Ｄ。ＭＣ６８ＨＣ０...     

东芝、IBM、西门子联合开发256MbDRAM

东芝、ＩＢＭ、西门子联合开发２５６ＭｂＤＲＡＭ据日本《ＳｅｍｉｃｏｎｄｕｃｔｏｒＷｏｒｌｄ》１９９５年第８期报道，东芝、ＩＢＭ、西门子联合开发２５６ＭｂＤＲＡＭ。通过采用０．２５μｍＣＭＯＳ及单元阵列面积小型化技术，其芯片面积仅为２８５．５ｍｍ２。该...     

A／D与D／A转换器技术

Ａ／Ｄ与Ｄ／Ａ转换器技术ＷＤ９４５１１１０位１００Ｍ采样／秒流水线子区ＢｉＣ－ＭＯＳＡＤＣ＝Ａ１０－ｂ１００－Ｍｓａｍｐｌｅ／ｓｐｉｐｅｌｉｎｅｄ　ｓｕｂ－ｒａｎｇｉｎｇＢｉＣＭＯＳＡＤＣ［刊，英］／Ｓｏｎｅ，Ｋ．…／／ＩＥＥＥＪ．Ｓｏｌｉｄ－Ｓｔａ...     

区间C／I平衡多区蜂窝CDMA系统的性能

本文研究多区蜂窝ＣＤＭＡ系统的性能。采用区间载扰比（Ｃ／Ｉ）平衡技术控制移动台和基台的发射功率以补偿路径损失和对数阴影的综合影响，用蒙特卡诺模拟方法计算了区间Ｃ／Ｉ平衡蜂窝ＣＤＭＡ系统的中断概率，研究了相邻小区数和不同标准偏差的对数阴影对系统性能的影响以及微蜂窝ＣＤＭＡ系统的总用户数和小区数的关系，并同区内Ｃ／Ｉ平衡蜂窝ＣＤＭＡ系统的性能进行了比较。     

Statistics of adaptive nulling and use of the generalizedeigenrelation (GER) for modeling inhomogeneities in adaptive processing

This paper examines the integrity of the generalized eigenrelation (GER), which is an approach to assessing performance in an adaptive processing context involving covariance estimation when the adaptive processors are subject to undernulled interference. The GER is a mathematical relation, which if satisfied, often facilitates closed-form analysis of adaptive processors employing estimated covariances subject to inhomogeneities. The goal of this paper is to determine what impact this constraint has on the integrity of the adaptive nulling process. In order to examine the impact of the GER constraint on adaptive nulling, we establish fundamental statistical convergence properties of an adaptive null for the sample covariance-based (SCB) minimum variance distortionless response (MVDR) beamformer. Novel exact expressions relating the mean and variance of an adaptive null of a homogeneously trained beamformer to the mean and variance of a nonhomogeneous trained beamformer are derived. In addition, it is shown that the Reed et al. (1974) result for required sample support can be highly inaccurate under nonhomogeneous conditions. Indeed, the required sample support can at times depend directly on the power of the undernulled interference     

Adaptive antenna arrays for OFDM systems with cochannelinterference

Orthogonal frequency-division multiplexing (OFDM) is one of the promising techniques for future mobile wireless data systems. For OFDM systems with cochannel interference, adaptive antenna arrays can be used for interference suppression. This paper focuses on a key issue for adaptive antenna arrays, that is, parameter estimation for the minimum mean square error (MMSE) diversity combiner (DC). Using the instantaneous correlation estimation approach developed in the paper, an original parameter estimator for the MMSE-DC is derived. Based on the original estimator, we propose an enhanced parameter estimator. Extensive computer simulation demonstrates that the MMSE-DC using the proposed parameter estimators can effectively suppress both synchronous and asynchronous interference in OFDM systems for packet and continuous data transmission     

Adaptive Detection and Estimation in the Presence of Useful Signal and Interference Mismatches

This paper considers adaptive detection and estimation in the presence of useful signal and interference mismatches. We assume a homogeneous environment where the random disturbance components from the primary and secondary data share the same covariance matrix. Moreover, the data under test contains a deterministic interference vector in addition to the possible useful signal. We focus on the situation where an energy fraction of both the useful signal and the deterministic interference may lie outside their nominal subspaces (conical uncertainty model). Under these conditions, we devise a procedure for the computation of the joint maximum likelihood (ML) estimators of the useful signal and interference vectors, resorting to a suitable rank-one decomposition of a semidefinite program (SDP) problem optimal solution. Hence, we use the aforementioned estimators for the synthesis of adaptive receivers based on different generalized likelihood ratio test (GLRT) criteria. At the analysis stage, we assess the performance of the new detectors in comparison with some decision rules, available in open literature.      

Analysis of adaptive multistage interference cancellation for CDMAusing an improved Gaussian approximation

We consider a simple model for adaptive multistage interference cancellation within a CDMA system, and seek to develop an accurate analytical expression for the performance of this system. Previous work on interference cancellation has relied heavily on simulation techniques or a simple Gaussian approximation (GA). The standard GA ran lead to bit-error rate (BER) results which are optimistic for the conventional receiver, and this also occurs when the approximation is applied to the interference cancellation problem. Additionally, this approximation does not allow the second order effects of the multiple access interference (MAI) to be included in the performance estimates. Several improvements on the standard GA have been suggested which result in accurate performance results for a standard CDMA receiver. This paper presents an analytical expression for the probability of bit error for an adaptive multistage interference canceller, using an improved Gaussian approximation (IGA) for MAI. The BER at any stage of interference cancellation can be recursively computed from the signal-to-noise ratio (SNR), the statistics of the random powers of users, and the processing gain of the CDMA system. The performance of the resulting EER expression is compared with simulation results. Since the second order effects of MAI can be included, the analytical framework presented here can also be used to evaluate the performance of multistage interference cancellation in arbitrary fading environments, and we present results for the performance of interference cancellation in lognormal fading environments     

An orthogonalized blind algorithm for hybrid of adaptive array and equalizer

The problems generated by the interference will be more complicated in the future. A combination of adaptive array and equalizer has been employed to solve the problems of interference when an adaptive array alone cannot suppress all the interferences. A constant modules algorithm (CMA) of the combination system was proposed to solve the problems of insufficient degrees of freedom and main‐beam multipath interference when no training signal is transmitted. The limitation of the CMA for combination systems is due to its slow rate of convergence. In this paper, an orthogonalized blind algorithm for hybrid of array and equalizer (OBHAE) is proposed to combat the problems of the interference. Because the modified input vector of the adaptive array is orthogonalized by the OBHAE in advance, the convergent rate of the CMA system can be improved by the OBHAE. When the coherent interference presents, the performance of the system will be degraded. In this paper, an orthogonalized spatial smoothing blind (OSSB) algorithm is proposed to further enhance the cancellation of the coherent interference. In the OSSB, we combine the OBHAE with the spatial smoothing method to combat the coherent interference problem. Simulation results are presented to demonstrate the merits of the OBHAE and the OSSB. Copyright © 2012 John Wiley & Sons, Ltd.     

一种低复杂性的自适应干扰消除接收机方案

本文提出一种适用于码分多址系统的低复杂度自适应干扰消除接收机。 在此接收机中，我们首先基于第i个用户的第m个比特的输出引入一组可靠度因子 ，然后根据这组可靠度因子估算出多址干扰，最后通过执行干扰消除可得到符号判决值。通过在加性高斯白噪声信道和多径衰落信道中进行仿真。结果表明，本文提出的这种接收机方案的性能优越于传统检测器和一些已经存在的干扰消除算法，同时保持有较低的算法复杂度。     

A Novel Adaptive Antenna Array for DS/CDMA Code Acquisition

Equipped with an adaptive beamformer, existing adaptive array code acquisition still relies on the correlator structure. Due to the inherent property of the associated serial-search scheme, its mean acquisition time is large, especially in strong interference environments. In this paper, we propose a novel adaptive filtering scheme to solve the problem. The proposed scheme comprises two adaptive filters, an adaptive spatial and an adaptive temporal filter. With a specially designed structure, the spatial filter can act as a beamformer suppressing interference, while the temporal filter can act as a code-delay estimator. A mean squared error (MSE) criterion is proposed such that these filters can be simultaneously adjusted by a stochastic gradient descent method. The performance as well as the convergence behavior of the proposed algorithm are analyzed in detail. Closed-form expressions for optimum filter weights, optimum beamformer signal-to-interference-plus-noise ratio (SINR), steady-state MSE, and mean acquisition time are derived for the additive white Gaussian noise (AWGN) channel. Computer simulations show that the mean acquisition time of the proposed algorithm is much shorter than that of the correlator-based approach, and the derived theoretical expressions are accurate.     

一种基于可变禁忌长度的多用户检测方法

CDMA系统的性能很大程度上受多用户干扰影响。多用户检测是抑制多用户干扰的有效方法。文中介绍一种基于可变禁忌长度的多用户检测方法。该方法以传统匹配滤波器的判决输出为初始解,采用禁忌长度可变的禁忌搜索(TS)算法,使禁忌长度与搜索空间的崎岖程度相适应,以避免搜索限入局部最优。仿真实验证明,该方法具有较好的误比特性能和抗远近效应能力,并具有多项式复杂度。     

自适应滤波技术在扩频通信系统抗窄带干扰中的应用

自适应滤波技术在扩频通信窄带干扰抑制的应用中,需要一种快速收敛的自适应算法以便能跟踪快速变化的干扰信号。文章提出将基于LSL自适应算法的格型滤波器应用于直接序列扩频通信系统中。仿真结果表明,LSL自适应算法在线性预测中具有快速收敛特性,并且在收敛过程中具有数值稳定性,从而显著改善了系统的抗窄带干扰能力。     

Orthogonalization based adaptive interference suppression fordirect-sequence code-division multiple-access systems

Rapid converging adaptive interference suppression algorithms for direct sequence code-division multiple-access (DS/CDMA) systems are presented after showing the limitations of conventional adaptive algorithms. The rapid converging algorithms are based on an orthogonal transformation preprocessing, and are adaptive implementations of the linear minimum mean square error (MMSE) receiver for interference suppression. These algorithms do not require a priori knowledge on interfering signal parameters such as spreading sequences and relative signal power levels