Design of Spring Coupling for High-$Q$ High-Frequency MEMS Filters for Wireless Applications

Abstract

A second-order microelectromechanical systems (MEMS) filter with high selectivity and sharp rolloff is required in wireless transceivers used in dense wireless sensor networks (WSNs). These sensors are expected to replace existing wired sensors used in industrial-plant management and environmental monitoring. These filters, together with MEMS-based oscillators and mixers, are expected to replace off-chip components and enable the development of a single-chip transceiver. Such a transceiver will leverage the integrated MEMS components' characteristics to operate at lower power and, hence, longer battery life, making autonomous WSNs more feasible in a wider range of applications. As a result, this paper presents the design and optimization of the coupling beam of wineglass-mode micromechanical disk filters using simulated annealing. The filter under consideration consists of two identical wineglass-mode disk resonators, mechanically coupled by a flexural-mode beam. The coupled two-resonator system exhibits two mechanical-resonance modes with closely spaced frequencies that define the filter passband. A constraint is added on the beam length to eliminate the effect of the coupling-beam mass on the filter's resonant frequency. A new process flow is proposed to realize self-aligned overhanging coupling beams designed in this paper. Index Terms-High-frequency microelectromechanical systems (MEMS), micromechanical filters, optimization, simulated annealing, spring coupling. NOMENCLATURE f o Resonance frequency. R Disk radius. ρ Material density. ν Poisson's ratio. E Young's modulus of elasticity. ω 0 = 2πf o Natural angular frequency. U Radial-displacement component. V Tangential-displacement component. m re Resonator effective mass. K re Resonator effective stiffness.

Exploiting nonlinearities of micro-machined resonators for filtering applications

“…There has also been active research on the improvement of various aspects of MEMS resonators for frequency filtering applications, such as producing high-Q, high-frequency, and highly selective filters, [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] Both electrically and mechanically coupled resonators have been demonstrated for filter applications. [10][11][12][13][14][15][16][17] Highly tunable filters were studied, where the centre frequency and the bandwidth can be tuned independently.…”

“…[10][11][12][13][14][15][16][17] Highly tunable filters were studied, where the centre frequency and the bandwidth can be tuned independently. [18][19][20][21][22][23] Furthermore, various designs of resonators have been explored, such as ring shaped and rectangular plate resonators, to achieve high-Q high-frequency filter operation.…”

A Coupled Resonator for Highly Tunable and Amplified Mixer/Filter

“…These include thin film bulk wave acoustic resonators [8], aluminum nitride (AlN) based rectangular plate and ring-shaped contour-mode resonators [9], and recently an AlN Lamé mode resonators [10]. Furthermore, mechanically and electrostatically coupled structures have been successfully used in such communication applications [10][11][12][13][14][15][16][17][18]. Considerable effort has been directed towards achieving a highly selective tunable filter, where the bandwidth and the center frequency can be tuned efficiently [19][20][21][22][23].…”

A Disparate Low Loss DC to 90 GHz Wideband Series Switch

“…Research communities have tried to address these reliability concerns and intercalated many approaches like seesaw structures [11], RF disk filter [12] and push-pull mechanism [13]. But the RF performance of these techniques was inferior because they were specifically designed for enhancing reliability.…”

“…In the proposed design, metal contact used is hard and has high melting point than the conventional metal and no dielectric have been used. The switch performance is better than [10][11][12][13] and operates on a wide frequency band.…”