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选取信道均衡器长度是均衡器设计的基本环节。简要介绍了所采用的无线传输信道模型和均衡器的结构,在此基础上提出了噪声环境下PSK信号接收均衡器长度的选取方法——符号判决差错率算法。给出了长度选取的流程图,并对信道举例进行计算和仿真,结果说明了选取方法的有效性。 相似文献
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当正交频分复用(OFDM)通信系统的循环保护前缀(CP)长度小于信道冲激响应长度时,常采用时域均衡方法消除符号间干扰(ISI)和子载波间干扰(ICI)。但时域均衡器结构复杂,且收敛速度较慢。为此,利用OFDM系统的零子载波信息,设计了一种频域均衡器。该均衡器具有稀疏矩阵结构,因此计算量小。理论分析和计算机仿真表明:它能有效消除由于循环前缀不足引起的符号间干扰和子载波间干扰,从而较好地恢复传输信号。 相似文献
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自适应均衡算法在信道均衡技术中的应用研究 总被引:5,自引:3,他引:2
文中描述了两种非线性均衡器分别为判决反馈均衡器(DFE)和最大似然序列估计(MLSE)均衡器.所用信道模型为加性白高斯噪声信道,在DFE和线性均衡器(LE)中都是使用递归最小二乘(RLS)算法和最小均方(LMS)算法对数据进行分块处理.MLSE均衡器中使用了维特比最佳译码算法.就误比特性能来做以比较,DFE远好于LE,MLSE均衡器又明显优于DFE,并且它能达到几乎最优的性能. 相似文献
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本文在分析判决反馈均衡器(DEF)和分数间隔均衡器(FSE)的基础上,提出了一种新型实用的判决反馈均衡器方案,设计出了实用的DFE硬件电路并给出了实验结果。 相似文献
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Convergence analysis of finite length blind adaptive equalizers 总被引:4,自引:0,他引:4
Ye Li Zhi Ding 《Signal Processing, IEEE Transactions on》1995,43(9):2120-2129
The paper presents some new analytical results on the convergence of two finite length blind adaptive channel equalizers, namely, the Godard equalizer and the Shalvi-Weinstein equalizer. First, a one-to-one correspondence in local minima is shown to exist between the Godard and Shalvi-Weinstein equalizers, hence establishing the equivalent relationship between the two algorithms. Convergence behaviors of finite length Godard and Shalvi-Weinstein equalizers are analyzed, and the potential stable equilibrium points are identified. The existence of undesirable stable equilibria for the finite length Shalvi-Weinstein equalizer is demonstrated through a simple example. It is proven that the points of convergence for both finite length equalizers depend on an initial kurtosis condition. It is also proven that when the length of equalizer is long enough and the initial equalizer setting satisfies the kurtosis condition, the equalizer will converge to a stable equilibrium near a desired global minimum. When the kurtosis condition is not satisfied, generally the equalizer will take longer to converge to a desired equilibrium given sufficiently many parameters and adequate initialization. The convergence analysis of the equalizers in PAM communication systems can be easily extended to the equalizers in QAM communication systems 相似文献
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ZHANG Yi GU Jian YANG Da-cheng Beijing University of Posts Telecommunications Beijing P.R. China 《中国邮电高校学报(英文版)》2005,12(2)
1IntroductionNext generation standards support high data rate ser-vices,in which users are only assigned a smaller-orderspreading code . This leads to a necessity for the tech-niques that suppress Inter-Chip Interference (ICI) aswell as Multi-Access Interference ( MAI) . The tradi-tional RAKE receiver experiences difficulty because theorthogonality decays when signal transmits over multi-path frequency selective fading channels . The RAKEreceiver cannot overcome the serious MAI and I… 相似文献
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Data communication systems are often beset with the problem of dc offset. The questions addressed and answered in this concise paper are: 1) can minimum mean-squared error (MMSE) equalizers correct dc offset? 2) what are the exact effects of the equalizer on offset, and offset on residual MSE? We conclude that MMSE equalizers can reduce the effects of dc offset but cannot completely eliminate them. Quantitative results give residual MSE as a function of offset magintude, equalizer length, and signal energy. 相似文献
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The existence of undesirable equilibria of Godard (1980) or constant modulus algorithms (CMA) is demonstrated for all finite-dimensional FIR equalizers. Sufficient stability conditions are presented for these equilibria. It is shown that for the Godard-2 algorithm, these undesirable equilibria are locally stable as long as the equalizer length remains finite. Results indicate that merely increasing the equalizer length does not necessarily nullify the potential for local convergence by Godard algorithms 相似文献
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Optimum space-time processors with dispersive interference: unifiedanalysis and required filter span
Ariyavisitakul S.L. Winters J.H. Inkyu Lee 《Communications, IEEE Transactions on》1999,47(7):1073-1083
We consider optimum space-time equalizers with unknown dispersive interference, consisting of a linear equalizer that both spatially and temporally whitens the interference and noise, followed by a decision-feedback equalizer or maximum-likelihood sequence estimator. We first present a unified analysis of the optimum space-time equalizer, and then show that, for typical fading channels with a given signal-to-noise ratio (SNR), near-optimum performance can be achieved with a finite-length equalizer. Expressions are given for the required filter span as a function of the dispersion length, number of cochannel interferers, number of antennas, and SNR, which are useful in the design of practical near-optimum space-time equalizers 相似文献
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Timing phase offset recovery based on dispersion minimization 总被引:1,自引:0,他引:1
Wonzoo Chung Sethares W.A. Johnson R. Jr. 《Signal Processing, IEEE Transactions on》2005,53(3):1097-1109
This paper presents a blind timing phase offset recovery scheme that attempts to optimize the baud spaced equalizer output mean square error (MSE) for a realistic equalizer length that is usually shorter than the ideal length. Among the existing blind timing recovery schemes, few are designed for equalizer output MSE optimization, and none are designed for the realistic case when the equalizer is short. The proposed algorithm (that is based on a cost function that minimizes the dispersion of the received signal) attempts to minimize the MSE of a one-tap equalizer output. It also exhibits good performance for relatively short equalizers. Conditions for the unimodality of the dispersion minimization cost are investigated, and a geometric relationship to the minimum MSE (MMSE) timing offset is shown qualitatively. The detailed MSE performance of the algorithm is investigated for the representing classes of channels by comparing existing blind timing offset estimation schemes. 相似文献
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Binh L.N. Thanh Liem Huynh Pang K.K. Sivahumaran T. 《Lightwave Technology, Journal of》2008,26(12):1586-1595
We propose maximum-likelihood sequence estimator (MLSE) equalizers based on either Viterbi algorithm or template matching temple matching (TM) for the equalization of impairments imposed on the minimum shift keying (MSK) modulation formats in long haul transmission without optical dispersion compensation. The TM-MLSE equalizer is proposed as a simplified alternative for the Viterbi-MLSE equalizer. It is verified that the Viterbi-MLSE equalizer can operate optimally when noise approaches a Gaussian distribution. Simulation results of the performances of the two MLSE equalizers for optical frequency discrimination receiver-based optical MSK systems are described. The transmission performance is evaluated in terms of: (1) the chromatic dispersion (CD) tolerance for both Viterbi-MLSE and TM-MLSE equalizers; (2) transmission distance limits of Viterbi-MLSE equalizers with various number of states; (3)the robustness to fiber polarization mode dispersion (PMD) of Viterbi-MLSE equalizers; and (4) performance improvements for Viterbi-MLSE equalizers when utilizing sampling schemes with two and four samples per bit over the conventional single sample per bit. With a small number of states (64 states), the non-compensating optical link can equivalently reach up to approximately 928 km SSMF for 10 Gb/s transmission or 58 km SSMF for 40 Gb/s. The performance of 16-state Viterbi-MLSE equalizers for optical frequency discrimination receiver (OFDR)-based optical MSK transmission systems for PMD mitigation is also numerically investigated. The performance of Viterbi-MLSE equalizers can be further improved by using the sampling schemes with multiple samples per bit compared to the conventional single sample bit. The equalizer also offers high robustness to fiber PMD impairment. 相似文献
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This paper evaluates the performance of Volterra equalizers and maximum-likelihood sequence detection (MLSD) receivers for compensation of signal distortion in nonlinear band-limited satellite systems. In addition, the performance of a receiver with a fractionally-spaced equalizer followed by a Volterra equalizer is studied (FSE-Volterra equalizer). For the equalizers, adaptation of the equalizer weights is considered including a multiple-step LMS algorithm which improves the convergence characteristics. Two MLSD receiver structures are considered: the optimum receiver consisting of a matched-filter bank followed by a Viterbi (1967) detector and a suboptimum receiver consisting of a single receiver filter followed by a Viterbi detector. The performance of the MLSD receivers is then compared to that of the equalizers 相似文献
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Kuan-Hung Chen Chun-Nan Chen Tzi-Dar Chiueh 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2005,52(12):816-820
With increasing demand for higher data rate, modern communication systems have grown more complex. Equalization has become more and more important as it is effective in mitigating the multipath fading often occurred in high-data-rate communication systems. However, the implementation complexity of adaptive equalizers is usually too high for mobile communication applications. In this paper, a novel adaptive equalization algorithm and its low-complexity architecture are proposed. This algorithm employs a new grouped signed power-of-two (GSPT) number representation. The GSPT algorithm and several enhanced versions are simulated as adaptive equalizers in a phase-shift keying communication receiver for several practical channels and the GSPT-based equalizers perform as well as the least mean square (LMS) equalizer. Moreover, for comparison, two GSPT-based equalizers and two other equalizers are implemented in field-programmable gate arrays. The GSPT-based equalizers require only about 25%-30% of the hardware resources needed in the LMS equalizer. Also the GSPT-based equalizers are more than twice as fast as the LMS equalizer. 相似文献
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《Microwave Theory and Techniques》1969,17(1):28-38
A general theory of transmission line all-pass equalizers operating in either TEM, TE, or TM modes is presented. Application of the theory to practical problems is straightforward, and circuit realizations of the equalizers are often simply related to easily computed design curves. Although the theory, strictly speaking, is for commensurate transmission line networks, it is not essential that the network being equalized, or in narrow-band cases the equalizer itself, be of commensurate length lines. Design formulas for narrow-band equalizers of up to two cavities are presented, and a method for extending the design to a greater number of cavities is described. The effect of equalizer dissipation loss is investigated and briefly described. Two example designs are presented. 相似文献