High Efficiency Power Supplies for Multi-mode RF Power Amplifiers in Cellular Handset Applications

Cellular handset evolution requires the front end transmitter to support multiple 3G/4G bands for global roaming, and also to be backward compatible with the existing 2G (quad-band GSM/EDGE) network. The cost and size would be prohibitive if one power amplifier (PA) only supports one band or if multiple supplies are required for multiple PAs. Solutions of interest are based on multi-standard multi-band PAs (e.g. 2 multi-mode PAs instead of 8+ mode-specific PAs), and an efficient power supply that supports these multi-mode PAs. The thesis starts with a study of PA supply architectures and DC-DC converters. A series architecture consisting of a boost converter followed by a buck converter has advantages of low-noise buck converter output, together with the ability to deliver full power at low battery voltages to extend the battery life. The buck converter presents a constant power load for the boost converter, which raises stability concerns. Small-signal control-to-output transfer functions are derived for peak or valley current mode controlled boost converter with a downstream regulated converter modeled as constant power load. It is shown how current mode control provides active damping to ensure stability and well-behaved dynamic response. Furthermore, it is shown how load current feedforward presents an effective way to improve power load transient response. Modeling and design approaches are validated by test circuit simulations, demonstrating stable operations using current mode control under constant power loads, and improved power step load transient response based on load current feedforward. A buck/boost and LDO series architecture is proposed as the solution to address efficiency, linearity, noise and time mask requirements for the supplies supporting multi-standard, multi-band PAs. A monolithic integrated circuit (IC) has been designed and implemented in a standard 0.5 5V CMOS process for supplying the multi-mode PAs. The buck/boost converter with wide output range delivers the peak efficiency of 92%. The power LDO has 1-4 MHz bandwidth, to support the GSM/EDGE/WCDMA time mask requirements and the polar EDGE operation. The test chip consumes the quiescent current 1.1 mA, and it delivers maximum 5 W output

Computationally efficient real-time digital predistortion architectures for envelope tracking power amplifiers

This paper presents and discusses two possible real-time digital predistortion (DPD) architectures suitable for envelope tracking (ET) power amplifiers (PAs) oriented at a final computationally efficient implementation in a field programmable gate array (FPGA) device. In ET systems, by using a shaping function is possible to modulate the supply voltage according to different criteria. One possibility is to use slower versions of the original RF signal’s envelope in order to relax the slew-rate (SR) and bandwidth (BW) requirements of the envelope amplifier (EA) or drain modulator. The nonlinear distortion that arises when performing ET with a supply voltage signal that follows both the original and the slow envelope will be presented, as well as the DPD function capable of compensating for these unwanted effects. Finally, two different approaches for efficiently implementing the DPD functions, a polynomial-based and a look-up table-based, will be discussed.Peer ReviewedPostprint (published version

Advances in Solid State Circuit Technologies

This book brings together contributions from experts in the fields to describe the current status of important topics in solid-state circuit technologies. It consists of 20 chapters which are grouped under the following categories: general information, circuits and devices, materials, and characterization techniques. These chapters have been written by renowned experts in the respective fields making this book valuable to the integrated circuits and materials science communities. It is intended for a diverse readership including electrical engineers and material scientists in the industry and academic institutions. Readers will be able to familiarize themselves with the latest technologies in the various fields

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

Large space structures and systems in the space station era: A bibliography with indexes (supplement 05)

Bibliographies and abstracts are listed for 1363 reports, articles, and other documents introduced into the NASA scientific and technical information system between January 1, 1991 and July 31, 1992. Topics covered include technology development and mission design according to system, interactive analysis and design, structural and thermal analysis and design, structural concepts and control systems, electronics, advanced materials, assembly concepts, propulsion and solar power satellite systems

Social work with airports passengers

Social work at the airport is in to offer to passengers social services. The main methodological position is that people are under stress, which characterized by a particular set of characteristics in appearance and behavior. In such circumstances passenger attracts in his actions some attention. Only person whom he trusts can help him with the documents or psychologically

Proceedings of the European Conference on Agricultural Engineering AgEng2021

This proceedings book results from the AgEng2021 Agricultural Engineering Conference under auspices of the European Society of Agricultural Engineers, held in an online format based on the University of Évora, Portugal, from 4 to 8 July 2021. This book contains the full papers of a selection of abstracts that were the base for the oral presentations and posters presented at the conference. Presentations were distributed in eleven thematic areas: Artificial Intelligence, data processing and management; Automation, robotics and sensor technology; Circular Economy; Education and Rural development; Energy and bioenergy; Integrated and sustainable Farming systems; New application technologies and mechanisation; Post-harvest technologies; Smart farming / Precision agriculture; Soil, land and water engineering; Sustainable production in Farm buildings