Author : Marcelo Jorge Franco
Publisher :
Page : 358 pages
File Size : 45,29 MB
Release : 2005
Category : Digital modulation
ISBN :
Author : Wan-Jong Kim
Publisher :
Page : 0 pages
File Size : 13,80 MB
Release : 2006
Category : Broadband communication systems
ISBN :
Power amplifiers are essential components in wireless communication systems and are inherently nonlinear. This nonlinearity generates spectral regrowth beyond the signal bandwidth, which in turn interferes with adjacent channels. Wideband code division multiple access (WCDMA) and orthogonal frequency division multiplexing (OFDM) systems are particularly vulnerable to nonlinear distortions; this is due to their high peak-to-average power ratios (PAPRs), which require a stringent linearity. One way to achieve the required linearity is to back-off the input signal. However, in the case of high PAPR signals, the efficiency of the power amplifier will be very low. In this dissertation, we are concerned with achieving high linearity and high efficiency. We first propose a predistorter based on piecewise pre-equalizers, for use in multi-channel wideband applications. This predistortion linearizer consists of piecewise pre-equalizers, along with a lookup table (LUT) based digital predistorter; together they compensate for nonlinearities, as well as memory effects of power amplifiers. Taking advantage of the multiple finite impulse response (FIR) filters, the complexity is significantly reduced when compared to memory polynomial methods. Furthermore, experimental results obtained when two WCDMA carriers were applied verified that our proposed method provides improvements comparable to those seen using the memory polynomial approach. Secondly, a unique baseband derived radio frequency (RF) predistortion system is presented, which uses LUT coefficients extracted at baseband to directly RF envelope modulate a quadrature vector modulator. The primary advantage of this architecture is that it combines the narrowband benefit of envelope predistortion with the accuracy of baseband predistortion. Finally, a novel efficient crest factor reduction technique for wideband applications is described. The technique uses peak cancellation to reduce the PAPR of the input signal. Conventional iterative peak cancellation requires several iterations to converge to the targeted PAPR, since filtering causes peak re-growth. The proposed algorithm eliminates several iterations and subsequently saves hardware resources. A direct performance comparison between a digitally predistorted and a feed-forward linearized Doherty amplifier is provided, under various crest factor reduction levels.
Author : Jingchang Nan
Publisher : CRC Press
Page : 217 pages
File Size : 25,82 MB
Release : 2021-07-30
Category : Technology & Engineering
ISBN : 1000409597
This book is a summary of a series of achievements made by the authors and colleagues in the areas of radio frequency power amplifier modeling (including neural Volterra series modeling, neural network modeling, X-parameter modeling), nonlinear analysis methods, and power amplifier predistortion technology over the past 10 years. The book is organized into ten chapters, which respectively describe an overview of research of power amplifier behavioral models and predistortion technology, nonlinear characteristics of power amplifiers, power amplifier behavioral models and the basis of nonlinear analysis, an overview of power amplifier predistortion, Volterra series modeling of power amplifiers, power amplifier modeling based on neural networks, power amplifier modeling with X-parameters, the modeling of other power amplifiers, nonlinear circuit analysis methods, and predistortion algorithms and applications. Blending theory with analysis, this book will provide researchers and RF/microwave engineering students with a valuable resource.
Author : Wangmyong Woo
Publisher :
Page : pages
File Size : 14,32 MB
Release : 2005
Category : Electric distortion
ISBN :
Hybrid Digital/RF Envelope Predistortion Linearization for High Power Amplifiers in Wireless Communication Systems Wangmyong Woo 151 Pages Directed by Dr. J. Stevenson Kenney. The objective of this research is to implement a hybrid digital/RF envelope predistortion linearization system for high-power amplifiers used in wireless communication systems. It is well known that RF PAs have AM/AM (amplitude modulation) and AM/PM (phase modulation) nonlinear characteristics. Moreover, the distortion components generated by a PA are not constant, but vary as a function of many input conditions such as amplitude, signal bandwidth, self-heating, aging, etc. Memory effects in response to past inputs cause a hysteresis in the nonlinear transfer characteristics of a PA. This hysteresis, in turn, creates uncertainty in predictive linearization techniques. To cope with these nonlinear characteristics, distortion variability, and uncertainty in linearization, an adaptive digital predistortion technique, a hybrid digital/RF envelope predistortion technique, an analog-based RF envelope predistortion technique, and a combinational digital/analog predistortion technique have been developed. A digital adaptation technique based on the error vector minimization of received PA output waveforms was developed. Also, an adaptive baseband-to-baseband test system for the characterization of RF PAs and for the validation of linearization algorithms was implemented in conjunction with the adaptation technique. To overcome disadvantages such as limited correction bandwidth and the need for a baseband input signal in digital predistortion, an adaptive, wideband RF envelope predistortion system was developed that incorporates a memoryless predistortion algorithm. This system is digitally controlled by a look-up table (LUT). Compared with conventional baseband digital approaches, this predistortion architecture has a correction bandwidth that is from 20 percent to 33 percent wider at the same clock speeds for third to fifth order IMDs and does not need a digital baseband input signal. For more accurate predistortion linearization for PAs with memory effects, an RF envelope predistortion system has been developed that uses a combination of analog-based envelope predistortion (APD) working in conjunction with digital LUT-based adaptive envelope predistortion (DPD). The resulting combination considerably decreases the computational complexity of the digital system and significantly improves linearity and efficiency at high power levels.
Author : John Wood
Publisher : Artech House
Page : 379 pages
File Size : 43,91 MB
Release : 2014-06-01
Category : Technology & Engineering
ISBN : 1608071200
Wireless voice and data communications have made great improvements, with connectivity now virtually ubiquitous. Users are demanding essentially perfect transmission and reception of voice and data. The infrastructure that supports this wide connectivity and nearly error-free delivery of information is complex, costly, and continually being improved. This resource describes the mathematical methods and practical implementations of linearization techniques for RF power amplifiers for mobile communications. This includes a review of RF power amplifier design for high efficiency operation. Readers are also provided with mathematical approaches to modeling nonlinear dynamical systems, which can be applied in the context of modeling the PA for identification in a pre-distortion system. This book also describes typical approaches to linearization and digital pre-distortion that are used in practice.
Author : Ibrahim Fatungase
Publisher :
Page : 0 pages
File Size : 41,78 MB
Release : 2023
Category :
ISBN :
This thesis provides a comprehensive study of linearity enhancement in Radio Frequency (RF) Power Amplifiers (PA) while transmitting wideband signals with a high Peak Average Power Ratio (PAPR). With the advancement of digital modulation techniques, signals with a highly variable envelope create challenges for the linearity of a transmitter's exciter electronics. The main focus of this work is on modeling existing Power Amplifier designs and improving their linearity to accommodate these advanced modulation techniques without violating spectrum emission requirements. A key aspect of this research involves the development and implementation of a memory polynomial pre-distortion method for the mitigation of memoryless nonlinearity, which is demonstrated to be effective through computational simulations and hardware implementation. The thesis also acknowledges existing challenges in addressing memory distortion, as it identifies specific areas where current methodologies fall short, underscoring the potential for continued research and innovation in this domain. Overall, this research holds significant implications for improving power efficiency and spectral efficiency in RF communication systems, which ultimately contributes to the advancement of wireless transmission technologies.
Author : Marie-Claude Fares
Publisher :
Page : pages
File Size : 13,37 MB
Release : 2009
Category :
ISBN :
Author : Fadhel M. Ghannouchi
Publisher : John Wiley & Sons
Page : 270 pages
File Size : 36,36 MB
Release : 2015-05-12
Category : Technology & Engineering
ISBN : 1119004446
Covers theoretical and practical aspects related to the behavioral modelling and predistortion of wireless transmitters and power amplifiers. It includes simulation software that enables the users to apply the theory presented in the book. In the first section, the reader is given the general background of nonlinear dynamic systems along with their behavioral modelling from all its aspects. In the second part, a comprehensive compilation of behavioral models formulations and structures is provided including memory polynomial based models, box oriented models such as Hammerstein-based and Wiener-based models, and neural networks-based models. The book will be a valuable resource for design engineers, industrial engineers, applications engineers, postgraduate students, and researchers working on power amplifiers modelling, linearization, and design.
Author : Marie-Claude Fares
Publisher :
Page : 78 pages
File Size : 39,91 MB
Release : 2009
Category :
ISBN :
Radio frequency (RF) communications are limited to a number of frequency bands scattered over the radio spectrum. Applications over such bands increasingly require more versatile, data extensive wireless communications that leads to the necessity of high bandwidth efficient interfaces, operating over wideband frequency ranges. Whether for a base station or mobile device, the regulations and adequate transmission of such schemes place stringent requirements on the design of transmitter front-ends. Increasingly strenuous and challenging hardware design criteria are to be met, especially so in the design of power amplifiers (PA), the bottle neck of the transmitter's design tradeoff between linearity and power efficiency. The power amplifier exhibits a nonideal behavior, characterized by both nonlinearity and memory effects, heavily affecting that tradeoff, and therefore requiring an effective linearization technique, namely Digital Predistortion (DPD). The effectiveness of the DPD is highly dependent on the modeling scheme used to compensate for the PA's nonideal behavior. In fact, its viability is determined by the scheme's accuracy and implementation complexity. Generic behavioral models for nonlinear systems with memory have been used, considering the PA as a black box, and requiring RF designers to perform extensive testing to determine the minimal complexity structure that achieves satisfactory results. This thesis first proposes a direct systematic approach based on the parallel Hammerstein structure to determine the exact number of coefficients needed in a DPD. Then a physical explanation of memory effects is detailed, which leads to a close-form expression for the characteristic behavior of the PA entirely based on circuit properties. The physical expression is implemented and tested as a modeling scheme. Moreover, a link between this formulation and the proven behavioral models is explored, namely the Volterra series and Memory Polynomial. The formulation shows the correlation between parameters of generic behavioral modeling schemes when applied to RF PAs and demonstrates redundancy based on the physical existence or absence of modeling terms, detailed for the proven Memory polynomial modeling and linearization scheme.
Author : Chao Yu
Publisher :
Page : 160 pages
File Size : 41,43 MB
Release : 2014
Category :
ISBN :
