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Binary-Coded 4.25-bit W-Band Monocrystalline-Silicon MEMS Multistage Dielectric-Block Phase Shifters
KTH, School of Electrical Engineering (EES), Microsystem Technology.
KTH, School of Electrical Engineering (EES), Microsystem Technology.ORCID iD: 0000-0001-9552-4234
KTH, School of Electrical Engineering (EES), Microsystem Technology.
2009 (English)In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 57, no 11, 2834-2840 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents a novel concept of a microwave microelectromechanical systems (MEMS) reconfigurable dielectric-block phase shifter with best loss/bit at the nominal frequency and best maximum return and insertion loss ever reported over the whole W-band. A seven-stage phase shifter is constructed by lambda/2-long high-resistivity silicon dielectric blocks, which can be moved vertically by MEMS electrostatic actuators based on highly reliable monocrystalline silicon flexures on-top of a 3-D micro-machined coplanar transmission line. The dielectric constant of each block is artificially tailor made by etching a periodic pattern into the structure. Stages of 15 degrees, 30 degrees, and 45 degrees are optimized for 75 GHz and put into a binary-coded 15 degrees + 30 degrees + 5 x 45 degrees configuration with a total phase shift of 270 degrees in 19 x 15 degrees steps (4.25 bits). Return and insertion losses are better than -17 and -3.5 dB at 75 GHz, corresponding to a loss of -0.82 dB bit, and a phase shift efficiency of 71.1 degrees/dB and 490.02 degrees/cm. Return and insertion losses are better than 12 and 4 dB for any phase combination up to 110 GHz (98.3 degrees/dB; 715.6 degrees/cm). The intercept point of third order, determined by nonlinearity measurements and intermodulation analysis, is 49.15 dBm for input power modulation from 10 to 40 dBm. The power handling is only limited by the transmission line itself since no current-limiting thin air-suspended metallic bridges as in conventional MEMS phase shifters are utilized. This is confirmed by temperature measurements at 40 dBm at 3 GHz with skin effect adjusted extrapolation to 75 GHz by electrothermal finite-element method simulations.

Place, publisher, year, edition, pages
2009. Vol. 57, no 11, 2834-2840 p.
Keyword [en]
Microelectromechanical systems (MEMS), microwave, millimeter wave, phase shifter, RF MEMS, x-band, intermodulation, capacitors, switches
URN: urn:nbn:se:kth:diva-18953DOI: 10.1109/tmtt.2009.2032350ISI: 000271678400024ScopusID: 2-s2.0-70450280774OAI: diva2:337000
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2012-04-27Bibliographically approved
In thesis
1. Novel RF MEMS Devices for W-Band Beam-Steering Front-Ends
Open this publication in new window or tab >>Novel RF MEMS Devices for W-Band Beam-Steering Front-Ends
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents novel millimeter-wave microelectromechanical-systems (MEMS) components for W-band reconfigurable beam-steering front-ends. The proposed MEMS components are novel monocrystalline-silicon dielectric-block phase shifters, and substrate-integrated three-dimensional (3D) micromachined helical antennas designed for the nominal frequency of 75 GHz.

The novel monocrystalline-silicon dielectric-block phase shifters are comprised of multi-stages of a tailor-made monocrystalline-silicon block suspended on top of a 3D micromachined coplanar-waveguide transmission line. The relative phase-shift is obtained by vertically pulling the suspended monocrystalline-silicon block down with an electrostatic actuator, resulting in a phase difference between the up and downstate of the silicon block. The phase-shifter prototypes were successfully implemented on a high-resistivity silicon substrate using standard cleanroom fabrication processes. The RF and non-linearity measurements indicate that this novel phase-shifter design has an excellent figure of merit that offers the best RF performance reported to date in terms of loss/bit at the nominal frequency, and maximum return and insertion loss over the whole W-band, as compared to other state-of-the-art MEMS phase shifters. Moreover, this novel design offers high power handling capability and superior mechanical stability compared to the conventional MEMS phase-shifter designs, since no thin moving metallic membranes are employed in the MEMS structures. This feature allows MEMS phase-shifter technology to be utilized in high-power applications. Furthermore, the return loss of the dielectric-block phase shifter can be minimized by appropriately varying the individual distance between each phase-shifting stage.

This thesis also investigates 3D micromachined substrate-integrated W-band helical antennas. In contrast to conventional on-chip antenna designs that only utilize the surface of the wafer, the novel helical radiator is fully embedded into the substrate, thereby utilizing the whole volume of the wafer and resulting in a compact high-gain antenna design. The performance of the antenna is substantially enhanced by properly etching the substrate, tailor making the antenna core, and by modifying size and geometry of the substrate-integrated ground plane. A linear line antenna array is composed of eight radiating elements and is demonstrated by simulations. Each antenna is connected to the input port through a multi-stage 3-dB power divider. The input and output of the single-stage 3-dB power divider is well matched to the 50-Ω impedance by four-section Chebyshev transformers. The simulation results indicate that the novel helical antenna arrays offer a narrow radiation beam with an excellent radiation gain that result in high-resolution scan angles on the azimuth plane. The proposed helical antenna structures can be fabricated by employing standard cleanroom micromachining processes.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. xii, 84 p.
Trita-EE, ISSN 1653-5146 ; 2012:011
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
urn:nbn:se:kth:diva-93507 (URN)978-91-7501-296-4 (ISBN)
Public defence
2012-05-25, Q1, Osquldas väg 4, entréplan, KTH, Stockholm, 09:30 (English)
QC 20120427Available from: 2012-04-27 Created: 2012-04-19 Last updated: 2012-04-27Bibliographically approved

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