Analysis and suppression of spurious modes of the ring shape anchored RF MEMS contour mode disk resonator

One of the most encumbering issues in RF MEMS resonators is spurious modes. The problem of spurious modes becomes more critical, when the ring type resonators are used. In the ring shape anchored contour mode disk resonator, for achieving a low serial resistance, the inner radius of the disk must be increased. This causes the spurious modes to become too close to the desired mode and degrade the operation of the resonator. In this work, spurious modes of before-mentioned device are introduced and their characteristics are evaluated by exact analytical approach. Based on those analytical approaches, we introduce two techniques for spurious mode suppression. The first technique is based on exciting the desired mode by proper electrode engineering and hence is an electrical approach. The second technique is reconfiguring of the anchor from a continuous ring to crossed ring segments and locating the segments on the phase discriminating lines to increase the insertion loss for spurious modes and decrease the losses for the fundamental mode. The final harmonic analysis verifies that the proposed techniques result a resonator with a pure frequency spectrum and spurious modes excluded over a very wide frequency range.     

Design of RF MEMS Based Oscillatory Neural Network for Ultra High Speed Associative Memories

Microelectromechanical systems are utilized alongside with transistor amplifiers and resistive connections for implementing of oscillatory associative memories. Phase locking is studied in such a network and all requirements of the circuit level implementation are satisfied. A very high gain trans-impedance amplifier operating in 1 GHz in addition to a novel automatic amplitude control circuit is employed to remove amplitude dynamics of the system. Requiring resonator characteristics are extracted and calculated as well. A new method for initialization of the network is proposed. Each neuron consumes 1.08 mW from a 1.8 V power supply. The convergence time of a typical network trained by Hebbian rule is less than 1.5 ns which results in an ultra high speed analog signal processing system.     

Analysis and suppression of spurious modes of the ring shape anchored RF MEMS contour mode disk resonator

One of the most encumbering issues in RF MEMS resonators is spurious modes. The problem of spurious modes becomes more critical, when the ring type resonators are used. In the ring shape anchored contour mode disk resonator, for achieving a low serial resistance, the inner radius of the disk must be increased. This causes the spurious modes to become too close to the desired mode and degrade the operation of the resonator. In this work, spurious modes of before-mentioned device are introduced and their characteristics are evaluated by exact analytical approach. Based on those analytical approaches, we introduce two techniques for spurious mode suppression. The first technique is based on exciting the desired mode by proper electrode engineering and hence is an electrical approach. The second technique is reconfiguring of the anchor from a continuous ring to crossed ring segments and locating the segments on the phase discriminating lines to increase the insertion loss for spurious modes and decrease the losses for the fundamental mode. The final harmonic analysis verifies that the proposed techniques result a resonator with a pure frequency spectrum and spurious modes excluded over a very wide frequency range.

     

Precise analytical evaluation of the ring shape anchored contour mode disk resonator for constructing a low noise UHF Pierce oscillator

This paper presents an analytical evaluation of the previously demonstrated Ring Shape Anchored Contour Mode Disk (RSACMD) resonator and extracts its equivalent electrical circuit. In the next step, a series resonant Pierce oscillator is designed and parameterized based on the calculated MEMS characteristics. Due to the inherent 180° of phase shift in the RSACMD resonator equivalent circuit, a modified version of a Pierce sustaining circuit is introduced with two inverters (instead of one inverter in conventional Pierce oscillators) to compensate that extra phase shift and satisfy Barkhausen criteria. The designed circuit presents excellent phase noise performance because of a special design which results in small frequency pulling and enable the circuit oscillate close to natural frequency of the high Q resonator. The overall circuit consumes less than 257 μW from a 1.8 V power supply.     

Design of a multi-frequency resonator for UHF multiband communication applications

A new structure for RF MEMS resonators is demonstrated in UHF range. The presented resonator has the ability to work in multiple resonance modes by its specific anchor design. Also, its special electrodes are designed so that the desired mode at any time could be excited by embedding simple MOS switches. Since the resonance frequency of different modes could be adjusted by the inner radius of the resonator, the structure could be designed for wide range of arbitrary frequency differences between modes. Specific electrodes and anchors design guarantees low insertion loss and high quality factor in all modes. Modal and harmonic analysis verify our approach.     

Correction to: Asymmetric RF MEMS resonant switch for high speed switching applications

Microsystem Technologies - Unfortunately, the affiliation details of the authors have been published incorrectly. The correct details are given below.     

Asymmetric RF MEMS resonant switch for high speed switching applications

Microsystem Technologies - Although micro-electro-mechanical switches are beneficial in small sizes, high levels of power handling, compatibility with CMOS process, wide bandwidth and zero power...     

Effects of Thermoelastic Damping on The Operation of The Ring Shape Anchored Contour Mode Disk Resonators

Thermoelastic damping is one of the most important energy loss mechanisms in MEMS resonators especially when the resonator is miniaturized to achieve higher frequencies. Based on thermal energy produced as the result of the resonator expansion and contraction, by considering the thermoelastic coupled equation, this article presents a solution to thermoelastic damping for previously demonstrated ring shape anchored contour mode disk RF MEMS resonator. This research proves that the thermoelastic damping has a negligible effect on the quality factor of the resonator. In addition the results mention that this effect becomes stronger when the surface to volume ratio is decreased for achieving higher frequency resonators. Obtained results reveal that the resonator could be utilized for ultra-low far-from-carrier phase noise oscillators.     

Design of a novel MEMS resonator based neuromorphic oscillator

A novel MEMS based neuromorphic oscillator is presented. Due to compatibility with CMOS process, on-chip integration of electro-statically actuated microresonators is possible with very small size. Also, taking advantage of sacrificial sidewall spacer technique for fabrication of 100 nm vertical gap, as low actuation voltages as 0.5 V is enough for such resonators. Oscillatory neuron dynamics are also studied and design of the resonator and its characteristics are described as a neuromorphic oscillator. There are several practical barriers associated with MEMS implementation of neuromorphic oscillators such as existence of near-to-main mode spurious modes, requiring of UHF high gain trans-impedance amplifier because of very high motional resistance of such resonators, and automatic amplitude control circuit which all investigated in the paper and surmounted as well. A coupling technique for weak connection of such resonators is also described in the paper which allows mechanical low velocity connection of UHF contour mode disk resonators for the first time.     

A new approach for the design of low velocity coupling for ring shape anchored contour mode disk resonators

The design of RF MEMS filters is a very important research area in the RF MEMS resonator field especially for UHF frequencies. Having very high Q and compatibility with the state-of-the-art CMOS technology, RF MEMS resonators could construct channel select filters in RF transceivers front-end and surmount the need for IF stages by direct conversion. But, there is a problem for coupling of high stiff contour mode disk resonators, because there is no nodal region at the perimeter of this kind of resonators for establishing the low velocity coupling without applying asymmetry on the resonance performance of the resonators. This paper introduces a pioneering technique for low velocity coupling of these resonators without any asymmetry. Analytical design approach and FEM analysis are provided in this paper and our discussions are verified by various simulations. The resulting filter could be designed to obtain 0.004?% of bandwidth with reasonable sizes which is completely enough for channel selection in low GSM standard.