Nonlinear modelling of radiofrequency devices for reconfigurable and sensing applications

Radiofrequency (RF) technologies have tremendously evolved in a bid to answer the ever-increasing demand for flexibility and efficiency of communication systems. In that respect, reconfigurability within a system plays the key role of dynamic adjustment to changing operation conditions: frequency bands, modulation schemes, and power levels. Reconfigurable RF systems are going to be fundamental in handling the challenges thrown up by modern communication networks, which include increasing data rate while improving spectrum efficiency and reducing energy consumption. Among the advanced materials that promise to provide RF reconfigurability are ferroelectric materials. In particular, a focus on the nonlinear modeling of Hafnium-Zirconium-Oxide-based (HfZrO) devices is presented, with particular attention to passive phase shifters. Moreover, the integration of HfZrO with complementary metal-oxide-semiconductor (CMOS) technology opens up a new generation of reconfigurable RF circuits. In this context, a new silicon-integrated technology for antenna realization and their derivative applications, such as RF Energy Harvesting (EH), is presented, focusing on the design and implementation of different rectennas operating at multiple frequencies. The topic of EH is also discussed in the framework of the design and realization of a novel topology for a wide dynamic range of applications. The need for stand-alone RF systems and circuits is of particular interest to microwave sensing applications. In particular, a focus on biological microwave sensing is presented. Two distinct solutions, for wood moisture content monitoring and skin hydration, are reported. Particular attention is given to a new sensing strategy that avoids the need for external instrumentation by only monitoring the steady-state regime of nonlinear circuits. Finally, a description of the activities carried out in joint projects with industry is reported, mainly focusing on the design of a novel positioning system for railway transport systems based on Long Range (LoRa) protocol and of a three-antenna system.