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Paraffin-Based RF Microsystems for Millimeter Wave Reconfigurable Antennas

Ghassemiparvin, Behnam
http://orcid.org/0000-0001-9313-6465
http://rave.ohiolink.edu/etdc/view?acc_num=osu157685881599312

Abstract Details

2020, Doctor of Philosophy, Ohio State University, Electrical and Computer Engineering.
With an increasing demand for high-speed wireless communication, current wire- less infrastructure cannot provide the bandwidth required for high-speed data transfer for multiple users. The next generation of millimeter-wave (mmW) communication systems operate in the frequency range of 30–300 GHz and can provide orders of magnitude greater bandwidth. In addition, these systems rely on adaptive strategies to achieve high data-rate communication which requires reconfigurable elements. In our research, we introduce a new class of reconfigurable radio frequency (RF) microsystems using paraffin phase-change material (PCM) that enables low-loss recon- figuration for mmW components. Paraffin (alkane) is a low-loss nonpolar dielectric that undergoes a 15% reversible volume change through its solid to liquid phase transition. Using this unique combination of loss characteristics and mechanical properties, we have developed continuously variable capacitors. These electro-thermally actuated variable capacitors are low loss with series resistance of less than 0.7 Ω at the mmW band and can be monolithically integrated with antennas and RF components to introduce reconfiguration. In this work, we present a frequency reconfigurable slot antenna which covers the 94 GHz–102 GHz band. In order to achieve reconfiguration, the slot antenna is loaded with two paraffin PCM capacitors. The capacitors are actuated using joule heaters and with the increase in temperature, paraffin goes through a solid to liquid transition. As the volume of the paraffin increases, the capacitance decreases continuously by approximately 15%, which results in increasing the resonance frequency. The realized gain of the antenna at 100 GHz is 3 dBi and it is approximately constant over the reconfiguration range. The Efficiency of the antenna is >72% for the entire reconfiguration range thanks to the low dielectric loss of the paraffin. To evaluate the performance gains of the reconfigurable antennas, new payoff metrics are defined for each of pattern, polarization and frequency reconfiguration schemes. These figures-of-merit, capture both the increased diversity due to the reconfiguration states and the associated losses. In addition, a paraffin PCM based, continuously-tunable true-time delay phase shifter is designed and optimized. By periodically loading a coplanar waveguide transmission line with paraffin PCM variable capacitors, propagation constant along the line is varied and phase shift is achieved. A figure-of-merit of 74.8◦/dB is obtained while maintaining a return loss more than 15 dB. Designed phase shifter has a maximum insertion loss of 4.8 dB for a 360◦ phase shift at 100 GHz. To evaluate the actuation performance of the PCM device, a fully-coupled multiphysics simulation is developed. To simulate the electro-thermo-mechanical actuation, four physics modules including, electric currents, heat transfer, laminar flow and solid mechanics are coupled. To characterize the dielectric properties of paraffin at the mmW band, a model- based characterization scheme using time-domain spectroscopy is proposed. Using this method, the relative dielectric constant of paraffin is measured to be 2.55 which is approximately constant over the frequency range of 26 GHz–1.2 THz. Loss tangent of paraffin is monotonically increasing with respect to frequency and it is estimated as 6.6 × 10−4 at 110 GHz. A six-layer photolithography process is used to realize mmW antennas and phase shifters, where all the components, including heater, antenna and capacitor are monolithically fabricated. Moreover, to deposit paraffin films, a new spin coating process is developed and characterized. Mechanical displacement of the paraffin PCM capacitors are measured using optical profilometer and maximum displacement of 1.4 µm is achieved. Reconfiguration capability of the antenna is measured using on-wafer probing and frequency shift in the range of 94–101 GHz is obtained. This work is the first demonstration of the paraffin-based reconfigurable mmW capacitor that is capable of continuous tuning.
Nima Ghalichechian, Professor (Advisor)
Khalil Waleed, Professor (Committee Member)
Kubilay Sertel, Professor (Committee Member)
Kisha Radliff, Professor (Committee Member)
158 p.
Electrical Engineering; Electromagnetics
millimeter wave; mmW; antennas; phase shifters; phase change material; paraffin; variable capacitor; microelectromechanical system; MEMS; multiphysics simulation;

Recommended Citations

Citations

  • Ghassemiparvin, B. (2020). Paraffin-Based RF Microsystems for Millimeter Wave Reconfigurable Antennas [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu157685881599312

    APA Style (7th edition)

  • Ghassemiparvin, Behnam. Paraffin-Based RF Microsystems for Millimeter Wave Reconfigurable Antennas. 2020. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu157685881599312.

    MLA Style (8th edition)

  • Ghassemiparvin, Behnam. "Paraffin-Based RF Microsystems for Millimeter Wave Reconfigurable Antennas." Doctoral dissertation, Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu157685881599312

    Chicago Manual of Style (17th edition)

osu157685881599312
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