Tesis doctoral de Lázaro Marco Platón
Rf power amplifiers (rfpa) are the most dominant power-consuming devices in battery-operated terminals for communication systems. Systems like gsm (global system for mobile communications) employ modulation schemes that generate constant amplitude rf outputs in order to allow use of high-efficiency switched-mode class-e rfpas. With the growing emphasis on channel capacity, the newer generation of communication systems (such as edge or wcdma) use non-constant envelope rf signals associated with spectrum-efficient digital modulations so as to increase the capacity. unfortunately, the amplification of non-constant envelope signals requires linear rf power amplifiers, which inherently have lower efficiency. the envelope elimination and restoration (or kahn) technique theoretically allows implementation of linear highly efficient rf power amplifiers. Eer technique considers separate power amplification paths for the polar representation of complex signals, namely the narrowband phase modulation signal rp(t) -by means of a tuned class e or class f rf efficient switching pa- and for the broadband baseband envelope signal e(t) -by means of a switching power converter, of the type usually applied to efficient dc-dc conversion-. With this configuration the rfpa supply is adaptively modulated so as to restore the envelope signal to the phase modulated signal, so that this technique is capable of providing overall high efficient linear power amplification. These combined features find application in modem digital modulations such as in edge and umts applications that exhibit significant envelope modulation, and are potentially suited to rf power amplification for multistandard and digital radio architectures several design challenges still preclude the complete success of this strategic technique. Envelope detector and limiter imperfections, delay mismatch through the two signal paths and am-pm distortion at the pa all degrade the system linearity. Though some of these issues have been addressed before, one of the key remaining challenges for a successful realization of such system is the practical implementation of the efficient, wide-bandwidth envelope-tracking power converter. in this thesis, the different factors which affect the performance of the envelope tracker are identified, and a figure of merit is proposed. A bridge between circuit parameters and system performance is established, developing a test bench which allows characterizing the performance, not only regarding communication standard requirements, but also in terms of efficiency. among other things, the fundamentals on pwm modulation are addressed, mainly regarding to its bandwidth and amplifying error. Different modulating signals have been considered and a generalized modulation~ratio criterion is defined. In order to decrease the bandwidth for a given error, pracompensation method is proposed. Considering the high performance of the sliding-mode control, its performance in terms of switching frequency and error is evaluated. Bearing in mind the envelope tracker application to a given standard, the power-bandwidth of the envelope is discussed, which justifies a that a low power bandwidth is required, as long as high frequency components are provided with low distortion, thus leading to the linear assisted case considering that the main aim is to obtain a high efficiency and high linearity, an efficiency model for buck converter-based amplifiers is provided, along with its extension to the linear assisted amplifier. On the other hand, it has been proved that the usual hnc-tone-test method to measure linearity cannot be applied successfully to the eer technique, due to its inherent infinite bandwidth envelope. The standard requirements have been taken into account in order to provide a design space evaluation, comprehending a procedure which allows concurrent design, which allows performing an optimization.
Datos académicos de la tesis doctoral «Translayer systems/circuit design-oriented co-characterization and optimization of alternative topologies and controls aiming envelope-tracking rf transmitters for future-generation mobile communications«
- Título de la tesis: Translayer systems/circuit design-oriented co-characterization and optimization of alternative topologies and controls aiming envelope-tracking rf transmitters for future-generation mobile communications
- Autor: Lázaro Marco Platón
- Universidad: Politécnica de catalunya
- Fecha de lectura de la tesis: 27/09/2010
Dirección y tribunal
- Director de la tesis
- Eduard Alarcon Cot
- Tribunal
- Presidente del tribunal: massimo Conti
- abdelali El aroudi (vocal)
- (vocal)
- (vocal)