RF Channel-Select Micromechanical Disk Filters-Part I: Design

• Published in: IEEE transactions on ultrasonics, ferroelectrics, and frequency control Vol. 66; no. 1; pp. 192 - 217
• Main Authors: Ozgurluk, Alper, Akgul, Mehmet, Nguyen, Clark T.-C.
• Format: Journal Article
• Language: English
• Published: United States IEEE 01.01.2019; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Band-pass filters; Bandpass filter (BPF); Bandwidth; Bandwidths; Circuit design; circuit model; Composite materials; coupling; Couplings; differential; Disk filters; frequency tuning; Insertion loss; insertion loss (IL); Integrated circuits; mechanical circuit design; MEMS resonator; Passband; quality factor; Radio frequency; Resonant frequency; Resonator filters; RF channel selection; small gap; Transistor circuits; Very large scale integration
• ISSN: 0885-3010; 1525-8955
• DOI: 10.1109/TUFFC.2018.2881727

This Part I of two papers introduces a design flow for micromechanical RF channel-select filters with tiny fractional bandwidths capable of eliminating strong adjacent channel blockers directly after the antenna, hence reducing the dynamic range requirement of subsequent stages in an RF front-end. Much like VLSI transistor circuit design, the mechanical circuit design flow described herein is hierarchical with a design stack built upon vibrating micromechanical disk building blocks capable of <inline-formula> <tex-math notation="LaTeX">{Q} </tex-math></inline-formula>'s exceeding 10 000 that enable low-filter passband loss for tiny fractional bandwidths. Array composites of half-wavelength coupled identical vibrating disks constitute a second level of hierarchy that reduces the filter termination impedance. A next level of hierarchy couples array composites with full-wavelength beams to affect fully balanced differential operation. Finally, identical differential blocks coupled with quarter-wavelength beams generate the desired passband. Part II of this study corroborates the efficacy of this design hierarchy via experimental results that introduce a 39-nm-gap capacitive transducer, voltage-controlled frequency tuning, and differential operation toward demonstration of a 0.1% bandwidth, 223.4-MHz channel-select filter with only 2.7 dB of in-band insertion loss and 50 dB of stopband rejection.