Design and implementation of an ETSI-SDR OFDM transmitter with power amplifier linearizer

Satellite radio has attained great popularity because of its wide range of geographical coverage and high signal quality as compared to the terrestrial broadcasts. Most Satellite Digital Radio (SDR) based systems favor multi-carrier transmission schemes, especially, orthogonal frequency division multiplexing (OFDM) transmission because of high data transfer rate and spectral efficiency. It is a challenging task to find a suitable platform that supports fast data rates and superior processing capabilities required for the development and deployment of the new SDR standards. Field programmable gate array (FPGA) devices have the potential to become suitable development platform for such standards. Another challenging factor in SDR systems is the distortion of variable envelope signals used in OFDM transmission by the nonlinear RF power amplifiers (PA) used in the base station transmitters. An attractive option is to use a linearizer that would compensate for the nonlinear effects of the PA. In this research, an OFDM transmitter, according to European Telecommunications Standard Institute (ETSI) SDR Technical Specifications 2007-2008, was designed and implemented on a low-cost Xilinx FPGA platform. A weakly nonlinear PA, operating in the L-band SDR frequency (1.450-1.490GHz), was used for signal transmission. An FPGA-based, low-cost, adaptive linearizer was designed and implemented based on the digital predistortion (DPD) reference design from Xilinx, to correct the distortion effects of the PA on the transmitted signal

Design and Implementation of a Software Predistorter for amplifier linearization in OFDM-based SDR systems

In modern wireless communication systems, an important role is played by the amplifier in the RF transmitter. It controls the maximum distance covered, the battery consumption for mobile devices, heating, etc. Nowadays RF transmitter has a lot of uses, starting from old FM stations, and arriving, in the recent period, to piloting of drones. Simplifying as much as possible, what this device accomplishes is to convert the baseband signal containing the data to be transmitted into a radio frequency signal able to travel through the ether. This can be done directly, or in two distinct phases before passing to an intermediate frequency (IF). In both cases, the signal after conversion must be amplified with a power amplifier and then transmitted on the channel. This thesis will focus on the amplifier part of the transmitter. In particular, existing predistortion techniques, used to improve the linearity of the power amplifier, and a software, non-real time, predistorter developed for the thesis will be described

Design and Linearization of Energy Efficiency Power Amplifier in Nonlinear OFDM Transmitter for LTE-5G Applications. Simulation and measurements of energy efficiency power amplifier in the presence of nonlinear OFDM transmitter system and digital predistortion based on Hammerstein-Wiener method

This research work has made an effort to understand a novel line of radio frequency power amplifiers (RFPAs) that address initiatives for efficiency enhancement and linearity compensation to harmonize the fifth generation (5G) campaign. The objective is to enhance the performance of an orthogonal frequency division multiplexing-long term evolution (OFDM-LTE) transmitter by reducing the nonlinear distortion of the RFPA. The first part of this work explores the design and implementation of 15.5 W class AB RF power amplifier, adopting a balanced technique to stimulate efficiency enhancement and redeeming exhibition of excessive power in the transmitter. Consequently, this work goes beyond improving efficiency over a linear RF power amplifier design; in which a comprehensive investigation on the fundamental and harmonic components of class F RF power amplifier using a load-pull approach to realise an optimum load impedance and the matching network is presented. The frequency bandwidth for both amplifiers was allocated to operate in the 2.620-2.690 GHz of mobile LTE applications. The second part explores the development of the behavioural model for the class AB power amplifier. A particular novel, Hammerstein-Wiener based model is proposed to describe the dynamic nonlinear behaviour of the power amplifier. The RF power amplifier nonlinear distortion is approximated using a new linear parameter approximation approach. The first and second-order Hammerstein-Wiener using the Normalised Least Mean Square Error (NLMSE) algorithm is used with the aim of easing the complexity of filtering process during linear memory cancellation. Moreover, an enhanced adaptive Wiener model is proposed to explore the nonlinear memory effect in the system. The proposed approach is able to balance between convergence speed and high-level accuracy when compared with behavioural modelling algorithms that are more complex in computation. Finally, the adaptive predistorter technique is implemented and verified in the OFDM transceiver test-bed. The results were compared against the computed one from MATLAB simulation for OFDM and 5G modulation transmitters. The results have confirmed the reliability of the model and the effectiveness of the proposed predistorter.Fundacão para a Ciência e a Tecnologia, Portugal, under European Union’s Horizon 2020 research and innovation programme ... grant agreement H2020-MSCA-ITN- 2016 SECRET-722424 I also acknowledge the role of the National Space Research and Development Agency (NASRDA) Sokoto State Government Petroleum Technology Trust Fund (PTDF

Design and implementation of an Envelope tracking Power Amplifier using switched Amplifiers and slow Envelopes

English: This master thesis presents the design and implementation of an Envelope Tracking (ET) transmitter including an envelope amplifier based on switched power amplifiers and algorithms for slew-rate and bandwidth reduction. The ET transmitter here presented constitutes a research environment that will allow investigate possible solutions to solve the linearity-efficiency trade-off of the power amplifiers. The design and implementation of the envelope amplifier includes commercial switching devices driven by pulsed signals generated by a Field Programmable Gate Array (FPGA). The pulsed signals are modulated using Pulse Width Modulation and Delta-Sigma Modulation aimed to achieve a high efficient amplification. The signals, amplitudes, modulation frequencies and bandwidths used during the design and implementation are compatible with current communications standards. This master thesis also presents a new algorithm for reduction of the envelope bandwidth as well as improvements over the existing slew-rate reduction algorithm presented in a previous publication. These improvements were implemented in the FPGA and validated in the implemented transmitter. Results show that switching amplification is limited by the availability of current technologies in this field and the algorithms for reducing slew rate and bandwidth of the envelope are suitable to overcome this limitation while new technologies allow higher switching frequencies

Novel DSP algorithms for adaptive feedforward power amplifier design.

Chan Kwok-po.Thesis (M.Phil.)--Chinese University of Hong Kong, 2003.Includes bibliographical references.Abstracts in English and Chinese.Abstract --- p.iAcknowledgement --- p.iiiChapter Chapter 1 --- Introduction --- p.1Chapter Chapter 2 --- Characterization of Nonlinearity in Power Amplifier --- p.6Chapter 2.1. --- Ideal Amplifier Representation --- p.6Chapter 2.2. --- Nonlinear Amplifier Representation --- p.7Chapter 2.2.1 --- Series Representation --- p.7Chapter 2.2.2 --- AM-AM and AM-PM Distortion --- p.7Chapter 2.2.3 --- Two-tone Intermodulation --- p.9Chapter 2.2.4 --- Nonlinearity on Digital Modulation Formats --- p.11Chapter Chapter 3 --- Linearization Techniques --- p.13Chapter 3.1. --- Power Back-off --- p.14Chapter 3.2. --- Feedback Technique --- p.15Chapter 3.3. --- Pre-distortion Technique --- p.16Chapter 3.4. --- Feed-forward Technique --- p.18Chapter 3.5. --- Linearization Systems with Signal Processing --- p.19Chapter 3.5.1 --- Envelope Elimination and Restoration (EER) --- p.19Chapter 3.5.2 --- Linear Amplification Using Nonlinear Components (LINC) --- p.20Chapter 3.5.3 --- Combined Analogue-locked Loop Universal Modulator (CALLUM) --- p.21Chapter 3.5.4 --- Linear Amplification Employing Sampling Techniques (LIST) --- p.21Chapter 3.6. --- Other Linearization Techniques --- p.22Chapter Chapter 4 --- Feed-forward Power Amplifier System --- p.23Chapter 4.1. --- General Description --- p.23Chapter 4.2. --- Adaptive Feed-forward Power Amplifier System --- p.25Chapter 4.2.1 --- Power Minimization --- p.28Chapter 4.2.2 --- Pilot Injection Technique --- p.29Chapter 4.2.3 --- Look-up-table Technique (Temperature Compensation) --- p.31Chapter 4.2.4 --- Correlation Based Feedback Control (Dual-loop) --- p.32Chapter 4.2.5 --- Correlation Based Feedback Control (Triple-loop) --- p.34Chapter 4.2.6 --- Digital Implementation on Adaptive FFPA --- p.35Chapter Chapter 5 --- DSP-based Adaptive FFPA Analysis --- p.37Chapter 5.1. --- System Architecture --- p.37Chapter 5.2. --- System Modeling --- p.39Chapter 5.3. --- Principle of Adaptation --- p.40Chapter 5.3.1 --- Adaptation in Error Extraction Loop --- p.40Chapter 5.3.2 --- Adaptation in Main-tone Suppression Loop --- p.43Chapter 5.3.3 --- Adaptation in Distortion Cancellation Loop --- p.44Chapter 5.3.4 --- Complex Adaptation --- p.46Chapter 5.4. --- Adaptation Performance Analysis --- p.47Chapter 5.4.1 --- Condition for Convergence --- p.47Chapter 5.4.2 --- Rate of Convergence --- p.48Chapter 5.4.3 --- Misadjustment --- p.49Chapter 5.4.4 --- Summary of the System Performance --- p.51Chapter 5.5. --- System Design Consideration --- p.51Chapter 5.5.1 --- Quadrature Sampling --- p.51Chapter 5.5.2 --- Data Processing --- p.52Chapter 5.6. --- Sensitivity Analysis --- p.55Chapter 5.6.1 --- Vector Representation --- p.55Chapter 5.6.2 --- Amplitude and Phase Matching --- p.56Chapter 5.6.3 --- Time-delay Matching --- p.58Chapter 5.7. --- Analog-to-digital Interface: Design Consideration --- p.60Chapter 5.7.1 --- Sampling Rate Consideration --- p.60Chapter 5.7.2 --- Finite Word-length --- p.61Chapter 5.8. --- Digital-to-analog Interface: Design Consideration --- p.63Chapter Chapter 6 --- New DSP Algorithms for High Performance Adaptive FFPA --- p.67Chapter 6.1. --- Variable Loop-gain Algorithm --- p.67Chapter 6.2. --- Variable Step-size Algorithm --- p.71Chapter 6.3. --- Least-mean-fourth Algorithm --- p.74Chapter Chapter 7 --- Implementation of DSP-based Adaptive FFPA --- p.79Chapter 7.1. --- Hardware Construction --- p.79Chapter 7.2. --- Experimental Results: LMS Algorithm --- p.82Chapter 7.3. --- Experimental Results: Variable Loop-gain Algorithm --- p.86Chapter 7.4. --- Experimental Results: Variable Step-size Algorithm --- p.88Chapter 7.5. --- Experimental Results: Lesat-mean-fourth Algorithm --- p.90Chapter Chapter 8 --- Conclusion --- p.92Appendix I Matlab Program for Computer Simulation of Adaptive FFPA --- p.A-lAppendix II DSP Program for Experimental Adaptive FFPA --- p.A-5References --- p.R-1Author's Publications --- p.AP-

LINC based amplifier architectures for power efficient wireless transmitters

Wireless communication trends Performance measuring of a communication system Power amplifiers and transmitters Power efficiency enhancement techniques Design and Optimization of LINC transmitter for OFDM applications LINC concept LINC signal decomposition LINC efficiency and combiner technologies Design optimization of LINC system Mismatch (imbalance) effects Advanced LINC transmitter architectures The 2X1 LINC transmitter system The 2X2 LINC transmitter system Mismatch effects

Rapid Dynamic Power Rail Switching of OFDM Signal Amplifiers

Global resource usage and allocation is becoming an increasingly critical topic. Efficiency is at the heart of a plethora of current research fields from reducing energy consumption in the manufacturing industry, to increasing energy generation from renewable sources, or reusing waste materials for alternative applications. The telecommunications industry is no different, OFDM as a modulation format is ubiquitous and popular due to its spectral efficiency and robustness to interference but its major drawback is its high peak-to-average power ratio (PAPR) meaning that its efficiency is compromised. A review of existing methods for improving OFDM signal amplifier efficiency showed a lack of innovative techniques for power supply control for such amplifiers. This thesis proposes two unique solutions to innovate efficiency for a range of applications. Firstly, a novel power supply control technique to improve the efficiency of OFDM signal amplifiers based on probabilistic analyses. The probability density function of an OFDM signal was analysed and optimum switching thresholds were determined to maximise the efficiency of the power supply. The proposed mechanism considers the theory of Golomb rulers and perfect difference sets, specifically the conversion from linear rulers to modular to achieve a much greater system implementation efficiency. The result is a dynamic fast-switching multi-level power supply which achieves the main benefits of Doherty and Chireix amplifiers but without requiring multiple amplifiers. This class A-G amplifier topology can achieve a 63% efficiency increase compared to amplifiers with single-level voltage supplies. Secondly, a generalised resource management technique known as Total Resource Utilisation Shuffling Technique (TRUST) to tackle the wider issue of resource utilisation and management. The focus for TRUST in this work is on batteries but it could be applied to a wide range of resources, not necessarily in the technology sector. Keywords: Chireix, Class A-G, Doherty, Golomb, OFDM, PAPR, PD