Microwave and millimeter-wave high-Q micromachined resonators

Alternative techniques for integrating high-quality factor resonators using micromachining techniques have been investigated. Two methods are presented which include suspending microstrip lines on thin dielectric membranes, resulting in an effective dielectric constant of near unity, and integrating three-dimensional micromachined waveguide cavity resonators with planar feedlines. These resonators show large improvements in quality factor over conventional techniques, and more importantly, allow for planar integration in complex systems. Resonators were fabricated in suspended microstrip at 29, 37, and 62 GHz with quality factors of over 450 with very close agreement between simulated and measured results. An integrated micromachined cavity resonator was also fabricated with a TE011 resonance quality factor of 1117 at 24 GHz and a TE021 resonance quality factor of 1163 at 38 GHz. To the authors' knowledge, these are the highest quality factor planar resonators without the use of superconductive materials, and can be used in microwave and millimeter-wave low-loss filters and low-phase-noise oscillators. ©1999 John Wiley & Sons, Inc. Int J RF and Microwave CAE 9: 326–337, 1999.