Fenomeni di distorsione non lineare e di instabilit\ue0 nelle antenne a microstriscia riconfigurabili mediante MEMS

none3noneV. Rizzoli; D. Masotti; F. MastriV. Rizzoli; D. Masotti; F. Mastr

Global stability analysis of nonlinear microwave circuits based on numerical implementation of bifurcation theory

The principal aim of the talk is to explain to a non-specialized audience the fundamentals of bifurcation theory and of its implementation in a microwave CAD environment in order to develop a self-consistent approach to the global stability analysis of nonlinear microwave circuits. The applications are intended to demonstrate that this technique allows a simple understanding of many difficult microwave design problems. The numerical implementation of Nyquist\u2019s analysis for the detection of the natural frequencies of a large-signal steady state is first addressed, and the differences between forced and autonomous circuits are examined in depth. The numerically efficient construction of solution paths in the state space of a parametrized circuit is then considered, and an automatic switching-parameter algorithm for automatically overcoming the turning points is introduced. The automatic search of the solution path for bifurcations and the development of a global stability pattern for the circuit under consideration is demonstrated, and the relationships between stability and noise are high-lighted. Several practical examples of application are provided, including the search and sup-pression of spurious tones in microwave oscillators and VCO\u2019s, the stability analysis of MEMS switching circuits under very large-signal drive, and the determination of the complex stability patterns of MEMS-reconfigurable microstrip antennas

Behavioural modelling of thermally induced distortion in RF/microwave nonlinear subsystems

Low-frequency thermal transients may give a relevant contribution to the generation of intermodulation distortion in nonlinear RF subsystems such as power amplifiers, where significant self-heating takes place. The pa-per discusses a simple and accurate behavioural model whereby such effects may be simulated with excellent ac-curacy and high computational speed. The model relies upon a parametric description of the relationships between the linear and nonlinear subsystem responses, and makes use of a relaxation method to efficiently evaluate the temperature waveforms

Analisi degli effetti non lineari nei circuiti a RF contenenti interruttori a MEMS

I MEMS (micromachined electromechanical systems) sono dispositivi allo stato solido con parti mobili azionate mediante segnali elettrici. Questi dispositivi possono essere inclusi in forma integrata nei front-end a radiofrequenza per sistemi di telecomunicazioni per realizzare varie funzioni (come interruttori, filtri a elevato Q, risonatori, ecc.) che altrimenti richiederebbero l\u2019uso di componenti esterni al chip. Una delle caratteristiche pi\uf9 interessanti dei dispositivi MEMS \ue8 rappresentata dalla loro maggiore linearit\ue0 rispetto ai corrispondenti componenti circuitali a semiconduttore. Nonostante ci\uf2, i MEMS presentano un complesso comportamento non lineare che pu\uf2 influenzare in modo sensibile le prestazioni del sistema in cui sono inseriti. Ci\uf2 risulta particolarmente evidente in presenza di forti segnali a RF modulati. Infatti, le costanti di tempo associate ai dispositivi MEMS normalmente sono molto grandi rispetto al periodo delle portanti a RF, ma in genere sono comparabili con il periodo dei segnali modulanti. La risposta non lineare del sistema elettromeccanico alle componenti a bassa frequenza dello spettro del segnale d\ue0 quindi origine a distorsione di intermodulazione. Lo studio di questi effetti \ue8 stato preso in esame in questo lavoro grazie allo sviluppo di un approccio innovativo che abbina alcune tecniche numeriche avanzate al metodo del bilanciamento armonico basato sulle variabili di stato e sulla scomposizione del circuito

Fast and robust inexact Newton approach to the harmonic-balance analysis of nonlinear microwave circuits

The letter discusses a novel approach to nonlinear microwave circuit simulation by the harmonic-balance (HB) technique. The nonlinear system is solved by an inexact Newton method, and the GMRES iteration is used at each step to find a suitable inexact Newton update. The peculiar structure of the Jacobian matrix allows the basis vectors of the Krylov subspace to be computed mostly by the FFT. The resulting simulation tool is fast and robust, and outperforms conventional HB techniques when applied to large-size nonlinear analysis problems

Magnetic Resonant Wireless Power Transfer

This chapter provides a general overview of magnetic resonant wireless power transfer systems based on network models. The power transferred to a receiver load at resonance is derived and explained. It is also shown the importance of using appropriate matching networks and how to design the oscillator and the load rectifie