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Study of intermodulation in RF MEMS variable capacitors
Girbau Sala, David; Otegi Urdanpilleta, Nerea; Pradell i Cara, Lluís; Lázaro Guillén, Antoni
Universitat Politècnica de Catalunya. Departament de Teoria del Senyal i Comunicacions; Universitat Politècnica de Catalunya. RF&MW - Grup de Recerca de sistemes, dispositius i materials de RF i microones
This paper provides a rigorous study of the causes and physical origins of intermodulation distortion (IMD) in RF microelectromechanical systems (MEMS) capacitors, its analytical dependence on the MEMS device design parameters, and its effects in RF systems. It is shown that not only third-order products exist, but also fifth order and higher. The high-order terms are mainly originated by the nonlinear membrane displacement versus applied voltage and, in the case considered in this study, with an additional contribution from the nonlinear dependence of the reflection coefficient phase on the displacement. It is also shown that the displacement nonlinear behavior also contributes to the total mean position of the membrane. In order to study these effects in depth, an analytical frequency-dependent IMD model for RF MEMS based on a mobile membrane is proposed and particularized to the case of a MEMS varactor-a device for which IMD can be significant. The model is validated, up to the fifth order, theoretically (using harmonic balance) and empirically (the IMD of a MEMS varactor is measured). To this end, a two-tone IMD reflection measurement system for MEMS is proposed.
Peer Reviewed
Àrees temàtiques de la UPC::Enginyeria de la telecomunicació::Radiocomunicació i exploració electromagnètica::Circuits de microones, radiofreqüència i ones mil·limètriques
MEMS (Microelectromechanical systems)
Microwave circuits
Intermodulation ensemble
Intermodulation distortion
Micromechanical devices
MEMS varactors
RF MEMS variable capacitor
Frequency-dependent IMD model
Harmonic balance
Intermodulation distortion
Microelectromechanical systems
Mobile membrane
Nonlinear dependence
nonlinear membrane displacement
Reflection coefficient phase
Two-tone IMD measurement
Sistemes microelectromecànics

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