OFDM系统中的一种自适应预失真器

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     

OFDM系统中的自适应预失真研究

随着移动通信中线性调制方法的出现,功率放大器的线性化成为一个重要的研究课题。提出一种用于正交频分复用(OFDM)系统中补偿由功率放大器引起的非线性失真的自适应预失真方法,并基于RASCAL算法,给出数字预失真器在OFDM中的实现结构,仿真表明该算法具有收敛速度快、补偿效果好的特点。     

OFDM系统中的自适应预失真研究

随着移动通信中线性调制方法的出现,功率放大器的线性化成为一个重要的研究课题.提出一种用于正交频分复用(OFDM)系统中补偿由功率放大器引起的非线性失真的自适应预失真方法,并基于RASCAL算法,给出数字预失真器在OFDM中的实现结构,仿真表明该算法具有收敛速度快、补偿效果好的特点.     

OFDM系统中的自适应预失真研究

随着移动通信中线性调制方法的出现，功率放大器的线性化成为一个重要的研究课题。提出一种用于正交频分复用（OFDM）系统中补偿由功率放大器引起的非线性失真的自适应预失真方法，并基于RASCAL算法，给出数字预失真器在OFDM中的实现结构，仿真表明该算法具有收敛速度快、补偿效果好的特点。     

0FDM系统中的一种自适应预失真器

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。     

一种自适应预失真器的实现及算法的改进

自适应数字预失真是补偿高功率放大器非线性的一种有效技术。本文基于RASCAL算法,给出了数字预失真器在OFDM系统中的实现结构,并对调整方法作了一些改进。通过仿真表明,改进的方法明显加快了收敛速度。     

基于放大器非线性拟合的自适应预失真技术

本文提出了一种新的有效的大功率放大器非线性失真的数字自适应预失真设计方法。该方法基于有理双线函数的非线性及其逆变换易于求解的特性，设计大功率放大器的估计器以逼近大功率放大器的非线性特性，预失真器的非线性参数由估计器的逼近函数逐段取逆变换来调节，以达到预失真补偿的目的。计算机仿真结果表明：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。     

查找表联合记忆效应补偿技术的宽带自适应预失真算法

为了能够对记忆型功率放大器线性化处理,并能一定程度克服其记忆效应,该文介绍一种自适应数字预失真器。该数字预失真器采用查找表与记忆效应补偿技术相结合的方法,并且利用内插值方法有效减小了查找表幅度量化过程产生的误差。相比记忆多项式预失真器,这种预失真器的计算复杂度较小,却能够得到与其相近的线性化效果。基于功率放大器记忆多项式模型,利用OFDM(Orthogonal Frequency Division Multiplexing)宽带信号验证该文提出的预失真器对记忆型非线性功率放大器的良好线性化效果。     

基于大功率放大器估计器的自适应预失真技术

本文提出了一种用于正交频分复用（OFDM）系统中由大功率放大器引起的非线性失真的有效的数字自适应补偿方法。该方法是通过对大功率放大器的非线性特性进行分段估计,然后对其逐段取逆变换来调节大功率放大器的预失真器的非线性参数,以达到预失真补偿的目的。计算机仿真结果表明:该方法具有收敛速度快、需要动态存储器（RAM）少、补偿效果好等特点。     

一种基于LS/SVD的基带预失真算法

自适应基带预失真技术是用于补偿高功率放大器非线性失真的一种有效技术。早期对预失真的研究大多局限于无记忆非线性,但对于OFDM等宽带应用,放大器的记忆效应明显。介绍了一种基于最小二乘奇异值分解(LS/SVD)的自适应算法来实现有记忆非线性功放的自适应基带预失真。仿真结果表明,该方案用于正交频分复用(OFDM)系统中能有效抑制带外频谱扩散,减小带内失真,实现有记忆非线性功率放大器的自适应预失真。     

Behavioral modeling of RF power amplifiers based on pruned volterra series

Behavioral modeling techniques provide a convenient and efficient means to predict system-level performance without the computational complexity of full circuit simulation or physics-level analysis of nonlinear systems, thereby significantly speeding up the analysis process. General Volterra series based models have been successfully applied for radio frequency (RF) power amplifier (PA) behavioral modeling, but their high complexity tends to limit their applications to "weakly" nonlinear systems. To model a PA with strong nonlinearities and long memory effects, for example, the general Volterra model involves a great number of coefficients. In this letter, we propose a new simplified Volterra series based model for RF power amplifiers by employing a "near-diagonality" pruning algorithm to remove the coefficients which are very small, or else not sensitive to the output error, therefore dramatically reducing the complexity of the behavioral model.     

Quantifying and cancelation memory effects in high power amplifier for OFDM systems

A modeling approach to power amplifier design for implementation in OFDM radio units is presented. The power amplifier model assesses the impact of linear memory effects within the system using a Wiener representation, and employs a linear novel parametric estimation technique using Hilbert space. In addition, in order to model the nonlinear memory effects the previous topology is generalized by inserting the truncated Volterra filter before the static nonlinearity. Predistortion based on the Hammerstein model is introduced to deal with the nonlinear response. The new general algorithm is proposed to evaluate the Hammerstein model parameters for an OFDM system. A representative test bed was designed and implemented. The assessment of the new methods for PA and PD modeling are confirmed by experimental measurements. The measurement results reveal the preference of the new techniques over the existing approaches.     

AN ALGEBRAIC ALGORITHM TO VOLTERRA SERIES REPRESENTATION OF A NONLINEAR NETWORK

It is important to solve the nth-order Volterra kernel or nonlinear transfer function indescribing a nonlinear network by the Volterra series.Based on an auxiliary algebraic expression ofthe Volterra series,an algebraic algorithm is proposed to evaluate the nth-order Volterra kernel andnonlinear transfer function in regular,triangular and symmetric forms.In addition,the complexity ofthe algebraic algorithm is improved.     

Si-LDMOS high power amplifier RFIC with integrated analogue pre-distorter

A simple approach to improve the linearity of silicon (Si) laterally diffused metal oxide semiconductor (LDMOS) base-station power amplifiers (PAs) by integrating an analogue pre-distorter (APD) is presented. The Si-LDMOS APD utilises an unequal power divider/combiner and Si-LDMOS field effect transistors to provide inverse distortion characteristics. Measurement shows that this method compensates for the nonlinear gain and phase compressions of the PA, thereby resulting in a 1.5 dB increase of the 1 dB compressed output power (P_-1dB).     

RoF非线性链路对OFDM信号的影响

正交频分复用OFDM（Orthogonal Frequency Division Multiplexing）与光载无线电ROF（Radio OverFiber）技术结合为实现低成本、高速数据传输的无线网络提供了可能。但RoF链路的非线性降低了系统性能。丈中在分析Machzehnder调制器的静态模型基础上,提出用Volterra级数与冲击响应分析模型相结合模型化RoF非线性系统。在此模型基础上分析Mach-Zehnder调制器以及射频放大器非线性对OFDM信号的影响。仿真分析显示非线性会使OFDM信号频谱展宽,降低信号幅度,并且随着光调制指数的增加误差矢量,带外干扰增加。为OFDM-RoF系统的线性化处理以及系统光调制器调制指教的选择提供了理论依据。     

Optimization of Third-Order Intermodulation Product and Output Power from an X-Band MESFET Amplifier Using Volterra Series Analysis

A third-order analysis for accurately predicting large-signal power and intermodulation distortion performance for GaAs MESFET amplifiers is presented. The analysis is carried out for both single- and two-tone input signals using the Volterra series representation and is based only on small-signal measurements. Simple expressions for the nonlinear power gain frequency response, the output power, the gain compression factor, and the third-order intermodulation (IM/sub 3/) power are presented. The major sources of gain compression and intermodulation distortion are identified. Based on the developed nonlinear analysis in conjunction with the device nonlinear model, a systematic procedure for designing a MESFET amplifier under large-signal conditions for optimum output power and IM/sub 3/ performance is proposed. The method utilizes out of band computed matching compensation through a nonlinear model of the amplifier. The accuracy of the device large-signal and IM/sub 3/ distortion characterization and the practicability of the proposed method are illustrated through comparison between measured and predicted results.     

非线性网络Volterra级数表示的代数求解算法

本文基于非线性网络Volterra级数表示的辅助代数方法,提出了非线性网络n阶Volterra核和n阶非线性传递函数的代数编列算法。求取了非线性网络的规范形、三角形、对称形n阶Volterra核及相应的n阶非线性传递函数,同时也降低了非线性网络Volterra级数表示编列算法的复杂性。     

SSPA自适应预失真器的设计方案

OFDM技术具有传输效率高和有效对抗多径衰落的优点,已经成为无线局域网标准的一部分.但OFDM信号有较大的峰值平均功率比,要求功率放大器具有很大的线性动态范围,否则直接影响着整个系统的运行成本和效率.针对固态功率放大器,提出了一种改进的基于查找表的自适应预失真方案.仿真结果表明,该方案有效地抑制了谐波分量和互调失真,对HPA的非线性有一定的改善,并且有效利用了硬件存储资源和提高了硬件运行速度.     

Adaptive algorithms for sparse system identification

In this paper, identification of sparse linear and nonlinear systems is considered via compressive sensing methods. Efficient algorithms are developed based on Kalman filtering and Expectation-Maximization. The proposed algorithms are applied to linear and nonlinear channels which are represented by sparse Volterra models and incorporate the effect of power amplifiers. Simulation studies confirm significant performance gains in comparison to conventional non-sparse methods.