RFM - RF & Microwaves Group

Overview

Both humans and machines tend to be universally connected, which requires wireless RF systems, mobile or embedded, capable of adapting to their environment application a global sense. RFM focuses on wireless technologies, able to provide the connectivity as optimally as possible, considering cost, energy efficiency, performance, flexibility and other major constraints or criteria.

The aim of the research is to investigate new concepts/models/techniques and innovate at several levels: components (antenna), characterization and modeling (power amplifier, radio channel, localization and radar) and communication schemes (modulation) for wireless communication systems.

Since 2009, the main axes developed by the RFM team have been :

 

This activity concentrates on the so-called ’RF front-end’, which is one of the most sensitive parts of communicating objects in terms of QoS and power consumption. It involves improved modulation/demodulations schemes as well as the study of automatic matching impedance circuits for antennas, dedicated to several wireless communication standards from 450 MHz to 40 GHz. Such matching circuits enable to achieve improved operating conditions for power amplifiers, owing to suitably developed advanced load and source pull techniques. Other works addressed the design of active radar front-ends intended for indoor detection of persons for security (airports, embassies...) and the development of a multi-antenna radio channel sounder based on 5-ports RF circuits.

Smart antennas have the potential to significantly increase the efficient use of the spectrum in wireless communication applications and to reduce antenna size, which is necessary for nomadic terminals as well as for airborne systems. This concept has been developed through the design of the antenna itself, in the frequency/angular/polarization domains (wideband /multiband, dual polarized antennas) and by integration of RF functions directly on the radiating elements. A particular attention has been given on metamaterials, which provide extra degrees of freedom in the design optimization, owing to novel physical properties. Small antennas interacting with their close environment, furthermore require dedicated design approaches, such as de-sensitization, which has been demonstrated to improve the overall performance of antennas on the human body.

 The increasing complexity and richness of wireless access to information systems requires more and more sophisticated radio channel models for a variety of environments and use cases. A better system optimization needs to consider jointly the propagation and the antennas and to be aware of the way these models will be used for wireless networks performance evaluation, given the realistic characteristics of RF transceivers and physical layer schemes. In particular, a novel approach, based on the statistical modeling of antennas and channel separately or jointly, has been developed and applied to a variety of contexts such as wireless local or cellular networks, body area networks and RFID systems. A new topic related to the enhancement of the security of wireless communications at the physical layer level, accounting for realistic propagation channels characteristics has been started in 2013 in the framework of the EC project PHYLAWS. Finally, another focus of the team concerns the development of a FMCW signal based localization technique for remote monitoring in indoor environments. 

 

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