Nano Science and Technology Institute
Nanotech 2002 Vol. 1
Nanotech 2002 Vol. 1
Technical Proceedings of the 2002 International Conference on Modeling and Simulation of Microsystems
Chapter 5: MEMS Applications and Characterization

Analysis of the Nonlinear Behavior of a MEMS Variable Capacitor

Authors:M. Innocent, P. Wambacq, S. Donnay, H. Tilmans, M. Engels, H. DeMan and W. Sansen
Affilation:IMEC, BE
Pages:234 - 237
Keywords:MEMS, varicap, resonator, nonlinear, Volterra series
Abstract:Today’s wireless communication systems often require a high linearity for the RF building blocks. One of these blocks can be a tunable LC filter using MEMS variable capacitors (varicaps). In these filters, the varicaps are the largest contributors to the nonlinearity. Therefore we analyze the frequency and bias dependence of the linearity of a MEMS varicap. Our analysis shows that two high frequency tones can only generate large unwanted intermodulation products in a MEMS varicap if they are close to each other. When the tones are widely separated, the nonlinear distortion can be much smaller than for other varicaps like MOS structures or junction capacitors. When the varicap is used in an LC tank (which is building block for a filter), the linearity of that tank decreases with increasing tank quality factor. This implies there is a trade-off between the linearity of a tunable LC filter and its selectivity and loss.
Analysis of the Nonlinear Behavior of a MEMS Variable CapacitorView PDF of paper
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