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

Linear Operation of Switch-Mode Outphasing Power Amplifiers

Radio transceivers are playing an increasingly important role in modern society. The ”connected” lifestyle has been enabled by modern wireless communications. The demand that has been placed on current wireless and cellular infrastructure requires increased spectral efficiency however this has come at the cost of power efficiency. This work investigates methods of improving wireless transceiver efficiency by enabling more efficient power amplifier architectures, specifically examining the role of switch-mode power amplifiers in macro cell scenarios. Our research focuses on the mechanisms within outphasing power amplifiers which prevent linear amplification. From the analysis it was clear that high power non-linear effects are correctable with currently available techniques however non-linear effects around the zero crossing point are not. As a result signal processing techniques for suppressing and avoiding non-linear operation in low power regions are explored. A novel method of digital pre-distortion is presented, and conventional techniques for linearisation are adapted for the particular needs of the outphasing power amplifier. More unconventional signal processing techniques are presented to aid linearisation of the outphasing power amplifier, both zero crossing and bandwidth expansion reduction methods are designed to avoid operation in nonlinear regions of the amplifiers. In combination with digital pre-distortion the techniques will improve linearisation efforts on outphasing systems with dynamic range and bandwidth constraints respectively. Our collaboration with NXP provided access to a digital outphasing power amplifier, enabling empirical analysis of non-linear behaviour and comparative analysis of behavioural modelling and linearisation efforts. The collaboration resulted in a bench mark for linear wideband operation of a digital outphasing power amplifier. The complimentary linearisation techniques, bandwidth expansion reduction and zero crossing reduction have been evaluated in both simulated and practical outphasing test benches. Initial results are promising and indicate that the benefits they provide are not limited to the outphasing amplifier architecture alone. Overall this thesis presents innovative analysis of the distortion mechanisms of the outphasing power amplifier, highlighting the sensitivity of the system to environmental effects. Practical and novel linearisation techniques are presented, with a focus on enabling wide band operation for modern communications standards

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

Digital Transmitter I/Q Calibration: Algorithms and Real-Time Prototype Implementation

Nowadays, the direct-conversion and the low-IF transceiver principles are seen as the most promising architectures for future flexible radios. Both architectures employ complex I/Q mixing for up- and downconversion. Consequently, the performance of the transceiver architectures can be seriously deteriorated by the phenomenon called I/Q imbalance. I/Q imbalance stems from relative amplitude and phase mismatch between the I- and Q-branches of the transceiver, thus resulting in self-interference or adjacent channel interference. This thesis addresses details of the real-time prototype implementation of the transmitter unit realizing a widely-linear least-squares-based I/Q imbalance estimation algorithm and a corresponding pre-distortion structure as previously proposed by Anttila et al. First transceiver architectures and radio transmitter principles are discussed with special emphasis on I/Q imbalance related aspects. Thereafter, the imbalance estimation principle itself is reviewed and a recursive version of it is derived. Then the implementation platform and software are introduced. After that, implementation details are discussed and implementation-related practical issues are addressed. Finally, simulation results and comprehensive RF measurement results from the real-time prototype implementation are presented. The work done in this thesis realizes a real-time prototype implementation of the WL-LS I/Q imbalance estimation algorithm and corresponding pre-distortion structure. In addition, the implementation is shown to give consistent results with Matlab simulations and it can operate on general purpose processors. /Kir10Nykyaikana suoramuunnos- ja matalavälitaajuuslähetin-vastaanotin periaatteet nähdään lupaavimpina arkkitehtuureina tulevaisuuden joustaville radioille. Molemmat arkkitehtuurit käyttävät taajuusmuunnoksissa kompleksista I/Q taajuus-sekoitusta. Tästä johtuen mainittujen lähetin-vastaanotinarkkitehtuurien suorituskykyä huonontaa ilmiö nimeltä I/Q epätasapaino, mikä johtuu suhteellisesta amplitudi ja vaihe epäsovituksesta modulaattorin I- ja Q-haarojen välillä. Tämän vuoksi signaaliin muodostuu itseishäiriötä tai viereisen kanavan häiriötä heikentäen radiotaajuisen signaalin puhtautta. Tässä diplomityössä esitellään reaaliaikaisen lähetin-vastaanotinprototyypin toteutus, jossa on käytössä Lauri Anttilan aiemmin julkaisema laajasti lineaariseen pienimmän neliösumman menetelmään perustuva I/Q epätasapainon estimointi algoritmi ja siihen liittyvä esivääristysrakenne. Aluksi esitellään lähetin-vastaanotinarkkitehtuurit ja niihin liittyvät pääperiaatteet painottaen I/Q epätasapainoon liittyviä asioita. Tämän jälkeen johdetaan I/Q epätasapainon estimointiin käytettävän algoritmin rekursiivinen versio ja esitellään toteutukseen käytettävä kehitysalusta ohjelmistoineen. Tämän jälkeen käydään läpi toteutuksen yksityiskohdat ja siihen liittyvät käytännön ilmiöt. Lopuksi esitellään simulaatiotulokset ja kokonaisvaltaiset radiotaajuusmittaukset reaali-aikaisesta prototyyppitoteutuksesta. Diplomityöprojektin tuloksena on radiolähettimen reaali-aikainen prototyyppi toteutus, jossa on käytössä laajasti lineaariseen pienimpään neliösummaan perustuva I/Q epäsovituksen estimointi ja vähentämis algoritmi. Implementaatio tuottaa yhdenmukaisia tuloksia Matlab simulaatioiden kanssa ja pystyy toimimaan yleiskäyttöisen suorittimen laskentateholla

Radio Communications

In the last decades the restless evolution of information and communication technologies (ICT) brought to a deep transformation of our habits. The growth of the Internet and the advances in hardware and software implementations modified our way to communicate and to share information. In this book, an overview of the major issues faced today by researchers in the field of radio communications is given through 35 high quality chapters written by specialists working in universities and research centers all over the world. Various aspects will be deeply discussed: channel modeling, beamforming, multiple antennas, cooperative networks, opportunistic scheduling, advanced admission control, handover management, systems performance assessment, routing issues in mobility conditions, localization, web security. Advanced techniques for the radio resource management will be discussed both in single and multiple radio technologies; either in infrastructure, mesh or ad hoc networks

Television broadcast from space systems: Technology, costs

Broadcast satellite systems are described. The technologies which are unique to both high power broadcast satellites and small TV receive-only earth terminals are also described. A cost assessment of both space and earth segments is included and appendices present both a computer model for satellite cost and the pertinent reported experience with the Japanese BSE