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对OFDM传输系统中大功率放大器非线性失真的数字自适应预失真技术进行了研究。利用有理双线性函数的非线性能较好地逼近大功率放大器的AM-AM或AM-PM非线性特性及其逆变换易于求解的特性,提出了一种新的数字自适应预失真方法,它是对估计器的输入幅度进行均匀量化,用一个估计器对大功率放大器的非线性特性进行估计,通过训练估计器的参数去调节预失真器的非线性参数,以达到预失真补偿的目的。与以前的方法比较,该方法用于正交频分复用(OFDM)系统中具有收敛速度快、系统性能稳定、补偿效果好等特点。 相似文献
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OFDM系统中的一种自适应预失真器 总被引:3,自引:1,他引:2
对OFDM传输系统中大功率放大器非线性失真的数字自适应预失真技术进行了研究。利用有理双线性函数的非线性能较好地逼近大功率放大器的AM AM或AM PM非线性特性及其逆变换易于求解的特性 ,提出了一种新的数字自适应预失真方法 ,它是对估计器的输入幅度进行均匀量化 ,用一个估计器对大功率放大器的非线性特性进行估计 ,通过训练估计器的参数去调节预失真器的非线性参数 ,以达到预失真补偿的目的。与以前的方法比较 ,该方法用于正交频分复用 (OFDM )系统中具有收敛速度快、系统性能稳定、补偿效果好等特点 相似文献
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采用预失真技术对功率放大器的记忆非线性失真进行补偿的关键是预失真器建模的准确性,尤其是模型对功率放大器逆记忆特性的描述能力。针对目前预失真器模型对功率放大器逆记忆效应描述不充分的问题,提出了将查找表(LUT)级联一个具有并联结构的有限长单位冲激响应(FIR)滤波器组作为实现形式的Hammerstein预失真器,以提高传统Hammerstein预失真器的补偿性能,并采用一种两步算法对其参数进行辨识。仿真实验表明,提出的Hammerstein预失真器能更好地补偿带强记忆效应的功率放大器的非线性失真。 相似文献
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新一代移动通信系统对于信道传输中的非线性失真十分敏感,功率放大器是产生非线性失真的主要器件。为了降低传输信号的失真程度,减小对相邻频段的用户的干扰,功率放大器的线性化技术显得尤其重要。预失真技术以其线性度好、自适应能力强、效率高等优点成为消除非线性失真的首选。在此阐述功率放大器的非线性特性和记忆效应,介绍预失真技术,利用基于Wiener模型的估计器来构成非直接预失真线性化系统,并对Wiener模型的参数识别算法进行优化。仿真实验表明此方法能有效补偿功率放大器的非线性失真和记忆效应,提高系统性能,降低开发成本。 相似文献
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数字基带预失真技术是克服高功率放大器非线性失真最有效的方法之一。早期对预失真技术的研究大多局限与无记忆非线性,但对于宽带和多载波应用。记忆非线性失真将不能再被忽略,无记忆预失真非线性补偿机制可能失效。文中研究了卫星通信系统中大功率记忆非线性功放的自适应基带预失真线性化技术,提出了一种基于记忆多项式的非直接学习结构的自适应基带预失真方案,给出了自适应算法。仿真结果表明,该方案能有效抑制带外频谱扩散,减小带内失真,降低误比特率,实现有记忆非线性大功率放大器的自适应预失真。 相似文献
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在宽带无线通信系统中,高功率放大器HPA因其非线性和记忆特性,将会导致频谱再生和邻道干扰。本文论述了在FPGA硬件平台上实现基于Volterra级数间接学习型的预失真器,采用LMS自适应算法在线实时更新预失真器的权重系数,从而有效消除高功率放大器的非线性失真。实验结果表明,该设计可以有效降低功放的互调失真(IMD),进而提高发射机系统的性能。 相似文献
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We introduce a plane, which we call the delta-sigma plane, that is indexed by the norm of the estimator bias gradient and the variance of the estimator. The norm of the bias gradient is related to the maximum variation in the estimator bias function over a neighborhood of parameter space. Using a uniform Cramer-Rao (CR) bound on estimator variance, a delta-sigma tradeoff curve is specified that defines an “unachievable region” of the delta-sigma plane for a specified statistical model. In order to place an estimator on this plane for comparison with the delta-sigma tradeoff curve, the estimator variance, bias gradient, and bias gradient norm must be evaluated. We present a simple and accurate method for experimentally determining the bias gradient norm based on applying a bootstrap estimator to a sample mean constructed from the gradient of the log-likelihood. We demonstrate the methods developed in this paper for linear Gaussian and nonlinear Poisson inverse problems 相似文献
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A general method is proposed for obtaining the inverse transfer function (for linear dynamic systems) and the inverse transfer characteristic (for nonlinear resistive circuits). The presented method makes use of nullors, known to be the most important active circuit elements. The procedure, initially introduced to obtain the system inversion for circuits already containing nullors, can easily be extended to any general circuit 相似文献
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In this paper we introduce a nonlinear equalizer using the Radial Basis Function (RBF) network with decision feedback equalizer (DFE) for electronic dispersion compensation in optical communication systems with on-off-keying and a direct detection receiver. The RBF method introduces a non-linear equalization technique suitable for optical communication direct detection systems that include nonlinear transformation at the photodetector. A bit error rate performance comparison shows that the RBF with DFE out performs the RBF without DFE and achieves similar results provided by maximum likelihood sequence estimator. 相似文献
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以宏纤维复合材料(MFC)驱动柔性悬臂结构为研究对象,着重开展其动态形状控制理论研究。基于有限单元法、均匀化理论和载荷比拟方法,建立了压电驱动层合结构力 电耦合动力学方程,并结合模态降阶法得到其状态空间形式控制模型。同时,针对压电材料作动器迟滞蠕变非线性特征对控制精度影响严重的问题,开展了依据实验数据的迟滞蠕变建模及其前馈逆补偿控制方法的研究,并构建了面向压电驱动柔性结构动态形状控制的迟滞 蠕变前馈补偿与自抗扰反馈控制相结合的复合控制系统。结果表明,该复合控制法能够在保证系统稳定性的前提下有效提高系统动态形状控制精度。 相似文献
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P. K. Chan D. Y. Chen 《IEEE transactions on circuits and systems. I, Regular papers》2007,54(1):119-129
This paper presents a new ion-sensitive field-effect transistor (ISFET ) readout circuit including a novel nonlinear temperature compensation method that is based on the theoretical work for formulating a body-effect-based ISFET drain current expression, the derivation of an unified temperature-dependent ISFET threshold voltage expression, and the use of iterative method for solving design parameters in nonlinear equations. Regarding the basic readout circuit, it comprises only one source follower and one current source to establish a self-biased configuration for a single ISFET device. Due to elimination of body effect, it displays linear transfer characteristic in the experimental result. Incorporating temperature compensation further improves the thermal stability of the ISFET device in pH sensing function. This has been validated by the experimental results on pH values ranging from 4 to 9 in a temperature range of 22 degC to 50 degC from the measurement setup. The pH7 parameter is used as a reference in the method. The proposed works are attractive in terms of circuit simplicity, temperature-compensated performance, cost and compatibility for smart sensor operation 相似文献