Linearizing E- Class Power Amplifier by Using Memoryless Pre-Distortion (original) (raw)

Radio Frequency Power Amplifiers (PA) are essential components of wireless systems and nonlinear in a permanent way. So, high efficiency and linearity at a time are imperative for power amplifiers. However, it is hard to obtain because high efficiency Power Amplifiers are nonlinear and linear Power Amplifiers have poor efficiency. To meet both linearity and efficiency, the linearization techniques such as Digital Predistortion (DPD) has arrested the most attention in industrial and academic sectors due to provide a compromising data between efficiency and linearity. This thesis proposed on digital predistortion techniques to control nonlinear distortion in radio frequency transmitters. By using predistortion technique, both linearity and efficiency can obtain. In this thesis a new generic Saleh model for use in memoryless nonlinear power amplifier (PA) behavioral modelling is used. The results are obtained by simulations through MATLAB and experiments. We explore the baseband 13.56 ...

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Behavioral Modeling and Digital Predistortion of Radio Frequency Power Amplifiers

The radio frequency power amplifier (RF-PA) within a digital wireless transmitter is a critical component regarding both the energy consumption and the signal quality. Especially due to today's broadband multicarrier modulation methods that generate signals with high peak-to-average power ratio, it is very hard to construct RF-PAs that achieve good energy efficiency and fulfill the strict linearity requirements imposed by the standard. Because of this, the digital predistortion (DPD) of RF-PAs has become a key technique for implementing energy efficient, high data rate wireless transmitters. This thesis investigates theoretical foundations and practical methods for the behavioral modeling and DPD of RF-PAs. The main contributions are a semi-physical model of the joint linearity-efficiency characteristics of RF-PAs, a detailed analysis of polynomial baseband models of RF-PAs focusing on the often neglected even-order terms in baseband, and a collection of practical methods for the dual-band DPD of RF-PAs. The trade-off between the linearity and efficiency of RF-PAs is investigated based on the semi-physical RF-PA model. For this purpose, linearity and efficiency quantification methods are introduced and applied to the model. Furthermore, an overview on highly efficient RF-PA operation modes and efficiency enhancement methods is given. A central result regarding polynomial baseband models is the first formal justification of even-order terms in baseband. This is achieved by deriving explicit passband-baseband pairs for the quasi-memoryless polynomial and the Volterra series, which show that even-order terms in baseband correspond to modified basis functionals in passband. Another central result of the presented analysis of polynomial baseband models is the formulation and proof of the phase homogeneity requirement, which represents a necessary symmetry of all complex baseband models of time-invariant passband systems. The practical methods for the dual-band DPD of RF-PAs include a method for dual-band crest factor reduction by clipping and error-filtering, a dual-band DPD model based on a vector-switched generalized memory polynomial, and a dual-band DPD training algorithm based on the indirect and direct learning architectures. These methods were implemented in MATLAB and validated at the 2017 DPD competition at the IEEE International Microwave Symposium, reaching the first place within the competition.

An Overview of RF Power Amplifier Digital Predistortion Techniques for Wireless Communication Systems

2012

This paper presents an overview of different Digital Predistortion (DPD) techniques used in microwave Power Amplifier (PA) linearization. Different DPD approaches are considered with both static and dynamic (memory effects) behavioral models. The most suitable solutions for facing the new challenges to linearize high-bandwidth amplifiers are discussed, which is demanded by most of the new telecommunications standards and emergent technologies.

Design of Digital Predistortion Technique for RF Power Amplifier using Memory Polynomial

Linearization of power amplifier has been an area of intense research from the last many years. The various types of linearization techniques are available for linearising PA but Digital Predistortion technique has been observed as one of the most common and effective method. But due to the issues like memory effects and exact characterization of non-linear behaviour of power amplifier, the implementation of existing predistortion technique suffers. So in this paper, a digital predistorter based on memory polynomial has been proposed that takes care of above mentioned issues. The presented technique is easy to implement and simple.

Digital predistortion of power amplifiers using look-up table method with memory effects for LTE wireless systems

EURASIP Journal on Wireless Communications and Networking, 2012

Digital predistortion (DPD) techniques are widely used to linearize of RF power amplifiers. In this article, a memory polynomial-based power has been modeled with memory order of 5 and nonlinearity order of 9. These specifications had been found suitable for advanced long-term evolution (LTE) wireless systems. A suitable DPD model was created based on the least square error minimization. Results for the complementary cumulative distribution function and normalized mean squared error were also computed. The adjacent channel leakage power ratio and error vector magnitude calculations showed that the proposed DPD for LTE system performed within the required limits as desired.

Linearization of RF power amplifiers using an enhanced memory polynomial predistorter

NORCHIP 2012, 2012

Radio frequency power amplifiers (PAs) play a keyrole in transceivers for mobile communications and their linearity is a crucial aspect. In order to meet the linearity requirements dictated by the standard at a reasonable efficiency, the usage of a linearization technique is required. In this paper we propose a linearization by means of a new type of digital predistorter, defined directly in the I-Q domain. The architecture of the proposed predistorter can be understood as an enhancement of the memory polynomial model (MPM) by means of additional I-Q terms. The usage of the proposed predistorter allows a more robust linearization of the whole RF transmitter because the enhancement of the model with additional I-Q terms can guarantee a more versatile compensation which is beneficial when the distortion comes from the joint contribution of the PA and the quadrature modulator. The proof of concept is achieved by measurements on a commercial PA in GaN technology and the performance of the proposed predistorter is illustrated.

A New Digital Predictive Predistorter for Behavioral Power Amplifier Linearization

IEEE Microwave and Wireless Components Letters, 2007

This letter presents a new digital adaptive predistorter (PD) for power amplifier (PA) linearization based on a nonlinear auto-regressive moving average (NARMA) structure. The distinctive characteristic of this PD is its straightforward deduction from the NARMA PA model, without the need of using an indirect learning approach to identify the PD function. The PD itself presents a NARMA structure, and hence it can be quickly implemented by means of lookup tables. Single and multicarrier modulated signals collected from a three-stage LDMOS class AB PA, with a maximum output power of 48-dBm CW have been used to validate the linearity performance of this new predictive predistorter.

Power amplifiers linearization based on digital predistortion with memory effects used in CDMA applications

2007

Digital predistortion of a baseband signal is a well-known method of power amplifier (PA) linearization used to reduce adjacent channel interference (ACI) in a non constant envelope modulation system. This paper discusses the application of adaptive digital baseband predistortion linearization to radio frequency (RF) power amplifiers (PAs) that exhibit memory effects. This technique is a highly cost- effective way to linearize Power amplifiers (PAs), but most existing architectures assume that the PA has a memoryless nonlinearity. For wider bandwidth applications such as wideband code-division multiple access (WCDMA) or wideband orthogonal frequency-division multiplexing (W- OFDM), PA memory effects can no longer be ignored. In this paper a new technique for adaptation of digital predistorter that considers memory effects in power amplifiers is proposed. This method is a combination of two techniques, memory polynomial predistortion and slope-dependent method. This new technique is validated by using a 1.9 GHz 60 W LDMOS power amplifier and various signals such as 2- carrier CDMA and 3-carrier CDMA.

On the Robustness of the Predistortion Function Synthesis for Highly Nonlinear RF Power Amplifiers Linearization

2006

This paper investigates the robustness of the digital predistortion function synthesis process applied to linearize a highly non linear RF power amplifier. For this purpose, a 100-watts peak power amplifier designed for UMTS applications biased in deep class AB is used. Two approaches have been compared: the polynomial curve fitting of the measured AM/AM and AM/PM characteristics and the look-up tables synthesis using the smoothed versions of these same non linear curves. The polynomial based fitting presents badly conditioned matrices that make this approach unpractical for the considered non linearity shape particularly for DSP implementation of the synthesis procedure. The accuracy of both approaches was assessed by measuring the adjacent channel power ratio at the output of the power amplifier under a 2carriers W-CDMA signal. The look-up tables approach based on the averaging technique showed better correction capabilities than the polynomial based fitting.

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