共查询到18条相似文献,搜索用时 60 毫秒
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符号定时同步是数字解调中一个重要的关键环节,实现快速符号定时同步后可减少信息帧报头的长度,提高帧的传输效率。本文基于报头的“10”码推导了一种快速定时同步方法,适合于工程中的数字化实现。 相似文献
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QAM全数字接收机载波相位恢复环路 总被引:2,自引:0,他引:2
本文着重研究全数字QAM接收机中载波恢复环路的设计,采用快慢两个数字环路来进行载波恢复,慢环路由锁频器(Frequency Detector),锁频锁相器(Phase and Frequency Detector)等组成,快环路由相痊解旋器和锁相器(Phase Detector)组成,仿真结果表明,在AWGN条件下,两个环路的环路参数设置存在一个最佳点,当两个环路工作在这个最佳点附近时接收机能够很好的进行载波频率,相位的恢复,相位噪声对接收机性能的影响最小,最后,给出了在不同信噪比下的最佳环路参数表。 相似文献
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全数字接收机中一种载波相位恢复的新方法 总被引:13,自引:1,他引:12
全数字接收机是在最近几年内提出的一个新的概念,它要求解调用的本地参考载波和采样时钟都振荡于固定的频率,不需要进行反馈控制,其他一些工作:载波相位误差和时钟定时误差的消除、信号的判定等全部由采样后的数字信号处理器完成。载波相位恢复问题和时钟同步问题是目前关于全数字接收机研究中的两个最主要的问题。本文仅讨论载波相位恢复问题。在本文中研究了载波相位估计算法中估计e~(jθ)和估计θ的差异,从理论上证明了估计e~(jθ)比估计θ有更好的统计特性,并且给出了一种估计e~(jθ)的方法,此方法有二个突出的优点:(1)它可以消除载波相位恢复过程中的相位区间跳变。(2)相位估计器的结构简单,它是全线性的,易于实现。利用16-QAM信号进行计算机仿真证实了此算法的可行性。 相似文献
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定时恢复是数字接收机同步系统的关键技术。经典数字接收机为防止最佳采样点抽取发生偏移造成接收信号散点图发散,往往通过锁相环控制抽样器以实现最佳采样点的抽取,而在全数字接收机中,最佳采样点是通过对采样信号进行插值计算得到的。全数字相位调制接收机定时恢复环路主要由平方定时相位偏差估计、定时控制单元和牛顿内插滤波器三部分组成。仿真结果充分表明该环路能够很好的实现MPSK、MQAM信号的定时恢复。 相似文献
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一种适用于QAM信号的符号同步方案 总被引:2,自引:0,他引:2
符号同步是全数字接收机中必须要完成的一项重要工作。找出一种算法相对简单,计算量小,估计精度高的符号同步方案,对于QAM信号的解调是十分有意义的。文章在对最大平均功率算法进行分析的基础上,提出一种联合估计方法,并对该方法进行了算法仿真,并进行了性能分析。 相似文献
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一种改进的QAM载波恢复方法 总被引:1,自引:1,他引:0
文中提出了一种新的QAM载波恢复环路结构。在此结构中频率检测和相位检测同时进行,在鉴相阶段引入了改进的加权直接判决(MWDD)算法。经仿真实验验证此方法提高了整个载波恢复环路的捕获速度,并使载波环路的相位抖动有所减小,16-QAM载波环路最大可以捕获11%符号率的频偏。 相似文献
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A fast symbol timing recovery (STR) scheme suitable for flexible-symbol-rate, burst-mode M-ary QAM (M-QAM) and PAM (M-PAM)
demodulators used in broadband communications is proposed. The maximum- likelihood (ML) estimation is used to derive a feed-forward
STR strategy to achieve fast and accurate derivation of the optimum timing instant with a very short training preamble for
applications requiring short packet transmission. In addition, the signal sample at the optimum timing instant is reproduced
by interpolation. Analysis to derive the ML-based timing estimation algorithm and STR structure is presented. Analytical models
are developed to evaluate the effects of imperfect interpolation and channel additive white Gaussian noise (AWGN) on the timing
estimation performance. The derived expressions can be used for optimum interpolation filter design and selection of key parameters
to achieve the required mean squared timing error. Simulation results are in good agreement with the analytical prediction. 相似文献
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文中针对短波高速QAM信号,提出并实现了一种全数字的解调方案。采用了最大平均功率定时同步算法和最大似然载波相位估计算法。利用同步导频使信号的眼图张开,进而对数据段进行信道均衡与相位补偿。采用判决反馈模式的非线性均衡器,更好地补偿了信道畸变。这种前向式解调结构减小了算法的复杂性,易于DSP实现。Matlab仿真结果表明该方案有效可行。 相似文献
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介绍了一种中频数字化PCM/FM接收机的定时误差恢复方法,它采用准最佳定时误差提取算法以及多项式内插器进行定时误差提取和纠正。计算机仿真结果表明,该方法是可行的,适合DSP实现。 相似文献
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在数字信号传输系统中,正交复用QAM(OMQAM)是目前最有效的一种抗信道失真传输技术,但它对系统的定时偏移和载波相位误差非常敏感。本文基于高阶累积量技术,导出了一种新的OMQAM系统定时和载波相位的跟踪算法。计算机仿真证实了这一理论分析结果,并同原有的Hirosaki算法做了比较 相似文献
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An algorithm to recover bit timing is proposed which maximises a quadratic polynomial approximation to the log-likelihood function. The exact equation for the mean of the log-likelihood function derivative, i.e. the S-curve, is derived and shown to have a sine form. In each time interval the S-curve has two zeros. The zero corresponding to the maximum of the likelihood function is resolved using quadratic interpolation based on four samples per period. The resulting timing synchroniser has a simple open loop feedforward structure which has effectively no acquisition period. Receiver performances in terms of rms timing jitter and bit error rate (BER) are analysed and shown to agree closely with theoretical results. 相似文献
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Axel Gesell Johannes B. Huber Berthold Lankl Georg Sebald 《AEUE-International Journal of Electronics and Communications》2002,56(5)
Timing phase estimation (TPE) plays the key role in feedforward (FF) symbol timing.For reasons of performance often data-aided (DA) methods are preferred. But frequently, they turn out to be critical with respect to theimplementation and the spectrum efficiency (due to the required overhead).This paper presents three DA TPE methods for quadrature pulse amplitude modulation (PAM). In spite of their very low complexity, these methods closelyapproach the theoretical limit for timing estimation with respect to the estimation variance, even at low SNR. This enables power efficient transmission.Further, they employ a CAZAC (constant amplitude, zero auto-correlation)sequence as training-sequence (TS), or a sequence with similar correlationproperties. Since such sequences are suited for almost all DA receiver tasks, a high spectrum efficiency can be obtained by the use of a single TS. A generalization of the proposed methods for DA TPE withrespect to the choice of the TS is also shown. The presented methods can be applied to noncoherent receivers. They are suited for high data-rate applications, since they can work with an oversampling factor of 2. 相似文献