Guest editorial for the special issue on software-defined radio transceivers and circuits for 5G wireless communications

Yichuang Sun, Baoyong Chi, and Heng Zhang, Guest Editorial for the Special Issue on Software-Defined Radio Transceivers and Circuits for 5G Wireless Communications, published in IEEEE Transactions on Circuits and Systems II: Express Briefs, Vol. 63 (1): 1-3, January 2016, doi: https://doi.org/10.1109/TCSII.2015.2506979.Peer reviewedFinal Accepted Versio

Contribution à l'étude et à la réalisation d'un générateur de signaux radiofréquences analogiques pour la radio logicielle intégrale

The increasing density of wireless devices and the associated communication flowssharing the same air interface will require a smart and agile use of frequency resources. Thisthesis proposes a flexible, low cost and low power disruptive transmitter architecture. It usesa differentiating coding scheme which leverages a mathematical and technological reduction ofthe energy cost of information conversion. The design of a DAC suited to this architecture isdeveloped and its performances are assessed toward RF signal generation. The measurementsof a demonstrator designed in 65 nm CMOS technology bring a proof of concept.Une utilisation intelligente de l’espace Hertzien sera nécessaire pour permettre aunombre croissant d’objets sans-fil connectés de communiquer dans le même espace de propagation.Ces travaux de thèse proposent une architecture d’émetteur radiofréquence flexible, faiblecoût et faible consommation, en rupture avec les techniques conventionnelles. Cet émetteur estfondé sur un encodage de la dérivée du signal à générer, ce qui permet de réduire le coût énergétiquede la conversion de l’information. Un convertisseur numérique analogique compatibleavec cette architecture est présenté et ses performances sont évaluées dans le cadre de la générationde signaux radiofréquence. Les résultats de mesures obtenus avec un prototype réalisé entechnologie CMOS 65 nm apporte la preuve du concept

Contribution à l’étude et la réalisation d’un générateur de signaux radiofréquences analogiques pour la radio logicielle intégrale

The increasing density of wireless devices and the associated communication flows sharing the same air interface will require a smart and agile use of frequency resources. This thesis proposes a flexible, low cost and low power disruptive transmitter architecture. It uses a differentiating coding scheme which leverages a mathematical and technological reduction of the energy cost of information conversion. The design of a DAC suited to this architecture is developed and its performances are assessed toward RF signal generation. The measurements of a demonstrator designed in 65 nm CMOS technology bring a proof of concept.Une utilisation intelligente de l’espace Hertzien sera nécessaire pour permettre au nombre croissant d’objets sans-fil connectés de communiquer dans le même espace de propagation. Ces travaux de thèse proposent une architecture d’émetteur radiofréquence flexible, faible coût et faible consommation, en rupture avec les techniques conventionnelles. Cet émetteur est fondé sur un encodage de la dérivée du signal à générer, ce qui permet de réduire le coût énergétique de la conversion de l’information. Un convertisseur numérique analogique compatible avec cette architecture est présenté et ses performances sont évaluées dans le cadre de la génération de signaux radiofréquence. Les résultats de mesures obtenus avec un prototype réalisé en technologie CMOS 65 nm apporte la preuve du concept

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