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Analysis of Linearity Deterioration in Multidevice RF MEMS Circuits
KTH, School of Electrical Engineering (EES), Micro and Nanosystems. (RF MEMS)ORCID iD: 0000-0002-8264-3231
KTH, School of Electrical Engineering (EES), Micro and Nanosystems. (RF MEMS)
KTH, School of Electrical Engineering (EES), Micro and Nanosystems. (RF MEMS)
2014 (English)In: IEEE Transactions on Electron Devices, ISSN 0018-9383, E-ISSN 1557-9646, Vol. 61, no 5, 1529-1535 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents for the first time an RF nonlinearity analysis of complex multidevice radio frequency microelectromechanical system (RF MEMS) circuits. The IIP3 of different RF MEMS multidevice tunable-circuit concepts including digital MEMS varactor banks, MEMS switched capacitor banks, distributed MEMS phase shifters, and MEMS tunable filters, is investigated. Closed-form analytical formulas for the IIP3 of MEMS multidevice circuit concepts are derived. A nonlinearity analysis, based on measured device parameters, is presented for exemplary circuits of the different concepts using a multidevice nonlinear electromechanical circuit model implemented in Agilent Advanced Design System. The results of the nonlinear electromechanical model are also compared with the calculated IIP3 using derived equations for the digital MEMS varactor bank and MEMS switched capacitor bank. The degradation of the overall circuit linearity with increasing number of device stages is also investigated, with the conclusion that the overall circuit IIP3 is reduced by half when doubling the number of stages, if proper design precautions are not taken. Design rules are presented so that the mechanical parameters and thus the IIP3 of the individual device stages can be optimized to achieve a higher overall IIP3 for the whole circuit. In addition, the nonlinearity of a novel MEMS tunable capacitor concept introduced by the authors, based on an MEMS actuator with discrete tuning steps, is discussed and the IIP3 is calculated using derived analytical formulas.

Place, publisher, year, edition, pages
2014. Vol. 61, no 5, 1529-1535 p.
Keyword [en]
Intermodulation distortion (IMD), RF MEMS, tunable capacitor, two-tone IIP3 measurement, MEMS varactor
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-143621DOI: 10.1109/TED.2014.2312215ISI: 000337753300046Scopus ID: 2-s2.0-84899994242OAI: oai:DiVA.org:kth-143621DiVA: diva2:707823
Note

QC 20140813

Available from: 2014-03-25 Created: 2014-03-25 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Novel RF MEMS Devices Enabled by Three-Dimensional Micromachining
Open this publication in new window or tab >>Novel RF MEMS Devices Enabled by Three-Dimensional Micromachining
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents novel radio frequency microelectromechanical (RF MEMS) circuits based on the three-dimensional (3-D) micromachined coplanar transmission lines whose geometry is re-configured by integrated microelectromechanical actuators. Two types of novel RF MEMS devices are proposed. The first is a concept of MEMS capacitors tuneable in multiple discrete and well-defined steps, implemented by in-plane moving of the ground side-walls of a 3-D micromachined coplanar waveguide transmission line. The MEMS actuators are completely embedded in the ground layer of the transmission line, and fabricated using a single-mask silicon-on-insulator (SOI) RF MEMS fabrication process. The resulting device achieves low insertion loss, a very high quality factor, high reliability, high linearity and high self actuation robustness. The second type introduces two novel concepts of area efficient, ultra-wideband, MEMS-reconfigurable coupled line directional couplers, whose coupling is tuned by mechanically changing the geometry of 3-D micromachined coupled transmission lines, utilizing integrated MEMS electrostatic actuators. The coupling is achieved by tuning both the ground and the signal line coupling, obtaining a large tuneable coupling ratio while maintaining an excellent impedance match, along with high isolation and a very high directivity over a very large bandwidth. This thesis also presents for the first time on RF nonlinearity analysis of complex multi-device RF MEMS circuits. Closed-form analytical formulas for the IIP3 of MEMS multi-device circuit concepts are derived. A nonlinearity analysis, based on these formulas and on  measured device parameters, is performed for different circuit concepts and compared to the simulation results of multi-device  conlinear electromechanical circuit models. The degradation of the overall circuit nonlinearity with increasing number of device stages is investigated. Design rules are presented so that the mechanical parameters and thus the IIP3 of the individual device stages can be optimized to achieve a highest overall IIP3 for the whole circuit.The thesis further investigates un-patterned ferromagnetic NiFe/AlN multilayer composites used as advanced magnetic core materials for on-chip inductances. The approach used is to increase the thickness of the ferromagnetic material without increasing its conductivity, by using multilayer NiFe and AlN sandwich structure. This suppresses the induced currents very effectively and at the same time increases the ferromagnetic resonance, which is by a factor of 7.1 higher than for homogeneous NiFe layers of same thickness. The so far highest permeability values above 1 GHz for on-chip integrated un-patterned NiFe layers were achieved.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. xiii, 79 p.
Series
TRITA-EE, ISSN 1653-5146 ; 2014:014
Keyword
Microelectromechanical systems, MEMS, Radio frequency microelectromechanical systems, RF MEMS, Micromachined transmission line, Micromachining, Tuneable capacitor, Switched capacitor, Coupled-line coupler, Tuneable directional coupler, Intermodulation distortion, MEMS varactor, Two-tone IIP3 measurement, Passive components and circuits, Reliability, Magnetic materials, NiFe multilayer composite, Permeability, Permittivity, Micromachined inductors
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:kth:diva-143757 (URN)978-91-7595-075-4 (ISBN)
Public defence
2014-04-24, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20140328

Available from: 2014-03-28 Created: 2014-03-27 Last updated: 2016-08-11Bibliographically approved

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