基于调制引入循环平稳的单信道盲辨识和盲抗干扰均衡

该文针对单输入单输出(Single-Input-Single-Output,SISO)信道,设计了一种特殊的引入多个共轭循环平稳的恒模复调制方案,使得接收机只需要一个接收天线就可以对FIR信道进行辨识(包括定阶)。利用辨识出的信道,可以进行循环维纳滤波均衡,具有很强的抗噪声(干扰)能力。     

一种多路并行盲搜索的空时二维抗干扰算法

针对卫星导航抗干扰中传统的空时自适应处理算法运算量大、处理速度较慢的问题,在介绍多级维纳滤波基本原理的基础上,提出了一种多路并行的盲搜索空时二维抗干扰自适应处理算法。该方法采用多级维纳滤波降维处理的方法求解信号子空间和干扰子空间,从而使输出信号的信干噪比达到最优,实现干扰的有效抑制。仿真结果表明,该算法具有较好的抗干扰性能,且运算量较低,有较好的工程应用前景。     

一种新颖的应用于无线局域网的小型化单极子天线

给出了一个新颖的三频工作的单极子天线,并可以应用于无线局域网。这个天线由对称结构和地板组成,它们分别印刷在介电常数为4.4、厚度为1.6 mm 的FR4 介质板的两面,并且采用微带线的馈电方式。这个天线有着小型化尺寸26 mm×20 mm×1.6 mm。测量结果显示,低频和高频的-10 dB 阻抗带宽分别为2.3-2.5 GHz 和4.7-6.8 GHz;这个 带宽覆盖了2.4/5.2/5.8 GHz 无线局域网工作频段。同时得到了较好的全向方向图。这个天线的低频和高频的平均增益分别为2dBi 和3.7dBi。     

一种结构新颖的半贴片宽带微带天线

设计了一种结构新颖的半贴片宽带微带天线。通过在圆形贴片上刻蚀两对环形槽,实现宽带特性,并在原有设计好的矩形贴片沿着馈电点所在的中轴线切掉一半贴片,减少了贴片一半面积,减小了尺寸。设计了这样一种半贴片宽带微带天线,不仅具有与原来全贴片基本相同的带宽特性,并且方向图与原天线基本相同,而且大大减小了天线尺寸。     

TD—SCDMA室外单基站非智能天线补盲优化性能研究

文章主要介绍了TD—SCDMA室外单基站非智能天线同频、异频补盲优化的相关问题,并以我国某大城市TD—SCDMA网络实际盲点为例,通过测试手段,对比补盲前和采用同、异频补盲后的网络覆盖、业务质量、切换和容量等网络性能变化情况,从而找出合理可行的补盲优化方案,给出研究结论和相关建议。     

一种基于盲均衡的新均衡器算法及实现

基于简化星座图(RCA)的盲均衡算法提出了一种新的均衡器算法———RCA-LMS算法,有效地结合了RCA算法和传统的最小均方(LMS)算法的优点,并应用于选择性反馈均衡器(selective feedback equalizer,SFE)结构,实现了RCA-LMS选择性反馈均衡器(RCA-LMSSFE)。仿真结果表明,该均衡器在低信噪比条件下,能较快地收敛,有较小的稳态剩余误差,从而有效地减小了信号的码间干扰,提高了通信系统的抗干扰能力。     

基于多天线接收的空间分集盲均衡算法

基于多天线接收的空间分集技术与均衡技术相结合的空间分集均衡算法可以克服衰落带来的不利影响,有效提高通信系统接收端的性能。文中将多天线支路间的合并权值和均衡器的权值统一合并于盲均衡算法中的系数估计,形成一种新的空间分集盲均衡算法,该算法具有较小的实现复杂度和很好的均衡效果。通过仿真实验表明,在误符号率相同的条件下,本文提出的分集均衡算法比单路信号盲均衡算法所需信噪比低1 dB-2 dB。同时分析了多天线接收的支路信号间存在的相位差以及延迟对算法的性能影响。     

一种新的天线阵列盲自适应波束形成算法

针对DS-CDMA的上行链路多用户检测,提出了一种基于天线阵列的盲自适应波束形成算法。针对强干扰采用线性约束最小方差准则(LCMV),利用正交分解将LCMV简化为非约束的最小化优化问题,采用共轭梯度(CG)算法求得最优解。对期望用户信号波形的使用保证了用户符号信息的最优恢复。仿真结果表明,该算法相对传统算法可以获得更高的信号干扰比(SINR)。该算法不需要天线阵列单元数大于用户数,因此具有更好的实用性。     

两种基于调制引入循环平稳的多用户系统盲检测研究

本文探讨了两种多用户系统的检测方法:第一种方法首先分别对各个用户的信道进行盲辨识,再进行多用户盲检测;第二种方法在收方利用频偏滤波(FRESH)的超强抗干扰能力,从收方混合多用户收信号中盲提取和盲分离出所需用户的收信号,再利用已辨识出的该用户的信道进行单用户盲检测。但这里的单用户检测不是普通的单用户检测,而是用了干扰抑制技术的新型检测,所以性能可以同多用户检测相当,克服了近远问题。     

Novel semi-blind ICI equalization algorithm for wireless OFDM systems

Intercarrier interference is deemed as one of the crucial problems in the wireless orthogonal frequency division multiplexing (OFDM) systems. The conventional ICI mitigation schemes involve the frequency-domain channel estimation or the additional coding, both of which require the spectral overhead and hence lead to the significant throughput reduction. Besides, the OFDM receivers using the ICI estimation rely on a large-dimensional matrix inverter with high computational complexity especially for many subcarriers such as digital video broadcasting (DVB) systems and wireless metropolitan-area networks (WMAN). To the best of our knowledge, no semi-blind ICI equalization has been addressed in the existing literature. Thus, in this paper, we propose a novel semi-blind ICI equalization scheme using the joint multiple matrix diagonalization (JMMD) algorithm to greatly reduce the intercarrier interference in OFDM. However, the well-known phase and permutation indeterminacies emerge in all blind equalization schemes. Hence we also design a few OFDM pilot blocks and propose an iterative identification method to determine the corresponding phase and permutation variants in our semi-blind scheme. Our semi-blind ICI equalization algorithm integrating the JMMD with the additional pilot-based iterative identification is very promising for the future high-throughput OFDM systems. Through Monte Carlo simulations, the QPSK-OFDM system with our proposed semi-blind ICI equalizer can achieve significantly better performance with symbol error rate reduction in several orders-of-magnitude. For the 16QAM-OFDM system, our scheme can also improve the performance over the plain OFDM system to some extent.     

Novel semi-blind channel estimation schemes for Rician fading MIMO channel

In this paper, we propose two novel semi-blind channel estimation techniques based on QR decomposition for Rician fading Multiple Input Multiple Output (MIMO) channel. In the first technique, the MIMO channel matrix H can be decomposed as an upper triangular matrix R and unitary rotation matrix Q as H = RQ. The matrix R is estimated blindly from only received data by using the orthogonal matrix triangularization based Householder QR decomposition, while the optimum rotation matrix Q is estimated exclusively from the algorithm of Orthogonal Pilot Maximum Likelihood Estimator (OPML) based on pilot information. In the second technique, the joint semi-blind channel and data estimation is performed by using the Least Square (LS) algorithm based on QR decomposition. The simulation results obtained for 4-PSK data modulation scheme using two transmitters and six receiver antennas for different Rice factor (K) have shown that the BER performance increases with an increase in the Rice factor. Finally, we compare these two new techniques with the conventional semi-blind channel estimation technique based on Whitening Rotation (WR), and the results show that the first proposed technique outperforms and the second technique achieves a very nearby performance as compared to the technique based on whitening rotation.     

Whitening-rotation-based semi-blind MIMO channel estimation

This paper proposes a whitening-rotation (WR)-based algorithm for semi-blind estimation of a complex flat-fading multi-input multi-output (MIMO) channel matrix H. The proposed algorithm is based on decomposition of H as the matrix product H=WQ/sup H/, where W is a whitening matrix and Q is unitary rotation matrix. The whitening matrix W can be estimated blind using only received data while Q is estimated exclusively from pilot symbols. Employing the results for the complex-constrained Cramer-Rao Bound (CC-CRB), it is shown that the lower bound on the mean-square error (MSE) in the estimate of H is directly proportional to its number of unconstrained parameters. Utilizing the bounds, the semi-blind scheme is shown to be very efficient when the number of receive antennas is greater than or equal to the number of transmit antennas. Closed-form expressions for the CRB of the semi-blind technique are presented. Algorithms for channel estimation based on the decomposition are also developed and analyzed. In particular, the properties of the constrained maximum-likelihood (ML) estimator of Q for an orthogonal pilot sequence is examined, and the constrained estimator for a general pilot sequence is derived. In addition, a Gaussian likelihood function is considered for the joint optimization of W and Q, and its performance is studied. Simulation results are presented to support the algorithms and analysis, and they demonstrate improved performance compared to exclusively training-based estimation.     

A single-antenna method for traceable antenna gain measurement

A simple method is introduced to measure the gain factor of a single preferably directional linearily polarized antenna in whatever distance. It requires only equipment for usual insertion loss measurement and the antenna itself in front of a totally reflecting surface simulating a second identical antenna as the image of the antenna to be calibrated. This speeds up such measurements considerably and, therefore, is very cost efficient. Its results can easily be made traceable to national standards     

半盲最小二乘恒模算法研究

恒模算法(CMA)是一种广泛应用于阵列处理、均衡、多用户检测中的盲算法.最小二乘恒模算法(LSCMA)由于其全局收敛性及稳定性受到关注.本文针对CDMA系统下行链路,基站知道小区内用户码字而小区外干扰用户码字未知的情形,提出一种适用的半盲LSCM多用户检测(MuD)算法.它将非盲多用户检测(本文中选用解相关MUD)与盲多用户检测技术(本文中选用LSCM检测器)相结合,首先根据小区内已知用户的信息,利用解相关MUD抵消小区内其它用户的干扰,接着利用LSCM算法抵消剩余的干扰.文中将SB-LSCM算法与已经提出的半盲解相关算法、LSCM算法和解相关算法进行了复杂度、SIR和BER性能的比较,并对SB-LSCM算法的SIR性能进行了理论分析.仿真结果表明SB-LSCM算法能够获得与半盲解相关相当的SIR的性能,但是其复杂度更低且在系统负荷大时能够获得优于半盲解相关算法的BER性能.另外,SB-SLCM算法能够获得较LSCM算法更快的收敛速度以及更加优良的性能.     

单天线连续波雷达发射泄漏噪声全链抑制技术

为提升单天线连续波雷达对弱小目标的远距离探测能力,分析了发射泄漏信号噪声对雷达检测性能的影响,提出了基于发射噪声全链抑制的解决方法。该方法首先在天馈链路中采用射频对消和反射对消技术抑制发射泄漏信号的功率电平,其次在接收机链路中采用相参混频噪声对消技术进一步遏制发射泄漏噪声对接收机热噪声的影响,最后在发射链路上采用超低相噪的波形产生技术控制发射噪声电平。整机试验结果表明,该方法应用到单天线连续波雷达中,不仅实现了对电力线等弱小目标的远距离探测,而且与同样功能的脉冲雷达相比具有更优的性能和装机适应性。     

The adaptive equalizer

This paper relates the author's experience in inventing the adaptive equalizer including how he addressed intersymbol interference and how he designed the adjustable filter.     

游戏情报站

枭雄、女娲传说、剑齿虎、NBA 2005（正式版）、熊猫的故事——挖竹笋、核金发条。     

让厨房“新鲜”一下

如果不是料理爱好者或者美食家，人们可能很难对厨房产生特别的感情。想到辛苦工作一天，回家后还要制作一顿晚餐，无疑又使你更加疲惫。厨房也可以很快乐，除了调整自身的心态外，有意思的厨房产品也能改变我们做料理时的心情。     

新鲜视角

家里的氛围会随着环境的改变而改变,如鲜花会带来自然而喜气的气氛,微亮的灯光会带来轻松平静的气氛……,一些家里的物品也同样可以改变家里的气氛,例如灯具、家具、个性的小家电等,用它们来充当家里的空间调剂师吧,让家里多些新鲜看点。