High Performance, Continuously Tunable Microwave Filters using MEMS Devices with Very Large, Controlled, Out-of-Plane Actuation

Software defined radios (SDR) in the microwave X and K bands offer the promise of low cost, programmable operation with real-time frequency agility. However, the real world in which such radios operate requires them to be able to detect nanowatt signals in the vicinity of 100 kW transmitters. This imposes the need for selective RF filters on the front end of the receiver to block the large, out of band RF signals so that the finite dynamic range of the SDR is not overwhelmed and the desired nanowatt signals can be detected and digitally processed. This is currently typically done with a number of narrow band filters that are switched in and out under program control. What is needed is a small, fast, wide tuning range, high Q, low loss filter that can continuously tune over large regions of the microwave spectrum. In this paper we show how extreme throw MEMS actuators can be used to build such filters operating up to 15 GHz and beyond. The key enabling attribute of our MEMS actuators is that they have large, controllable, out-of-plane actuation ranges of a millimeter or more. In a capacitance-post loaded cavity filter geometry, this gives sufficient precisely controllable motion to produce widely tunable devices in the 4-15 GHz regime.Comment: 12 pages 14 figures 2 table

VHF band-pass filter based on a single CMOS-MEMS doubleended tuning fork resonator

AbstractThis paper presents a single Double-Ended Tuning Fork (DETF) MEMS resonator-based band-pass filter fabricated on a commercial standard CMOS technology. The accurate design of this resonator demonstrates the ability to perform filtering without the need of coupling multiple resonators. The main characteristic is to define the out-of-phase mode resonance frequency of the DETF smaller than the in-phase mode frequency. The electrical characterization shows that this stand-alone band-pass filter presents a 44.4MHz central frequency with a 0.6% bandwidth in air

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

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 componentsÕ 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-beammass on the filterÕs resonant frequency. A new process flow is proposed to realize self-aligned overhanging coupling beams designed in this paper.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87260/4/Saitou6.pd

Multi-level and multi-objective design optimisation of a MEMS bandpass filter

Microelectromechanical system (MEMS) design is often complex, containing multiple disciplines but also conflicting objectives. Designers are often faced with the problem of balancing what objectives to focus upon and how to incorporate modeling and simulation tools across multiple levels of abstraction in the design optimization process. In particular due to the computational expense of some of these simulation methods there are restrictions on how much optimization can occur. In this paper we aim to demonstrate the application of multi-objective and multi-level design optimisation strategies to a MEMS bandpass filter. This provides for designers the ability to evolve solutions that can match multiple objectives. In order to address the problem of a computationally expensive design process a novel multi-level evaluation strategy is developed. In addition a new approach for bandpass filter modeling and optimization is presented based up the electrical equivalent circuit method. In order to demonstrate this approach a comparison is made to previous attempts to design similar bandpass filters. Results are comparable in design but at a significant reduction in functional evaluations, needing only 10,000 functional evaluations in comparison to 2.6 million with the previous work

Mechanical synchronization of MEMS electrostatically driven coupled beam filters

Micro-electromechanical systems (MEMS) bandpass filters based on arrays of electrostatically driven coupled beams have been demonstrated at MHz frequencies. High performance follows from the high Q-factor of mechanical resonators, and electrostatic transduction allows tuning, matching and actuation. For high-order filters, there is a conflict between the transduction mechanism and the coupling arrangement needed for dynamic synchronization: it is not possible to achieve synchronization and tuning simultaneously using a single voltage. Here we propose a general solution, based on the addition of mass-loaded beams at the ends of the array. These beams deflect for direct current (DC) voltages, and therefore allow electrostatic tuning, but do not respond to in-band alternating current (AC) voltages and hence do not interfere with synchronization. Spurious modes generated by these beams may be damped, leaving a good approximation to the desired response. The approach is introduced using a lumped element model and verified using stiffness matrix and finite element models for in-plane arrays with parallel plate drives and shown to be tolerant of the exact mass value. The principle may allow compensation of fabrication-induced variations in complex filters

Flexible Microelectromechanical filters for telecommunication electronics

The telecommunication electronics sector is under intensive growth and research owing to the much needed expansion in functionality and mobility. As part of this change, more flexible and multi-featured products are gaining popularity, paving the way for uninterrupted and high-speed mobile communications. As the telecommunication devices become lighter, smaller, and smarter, they pose stringent constraints and challenges to the researchers of integrated telecommunication electronics. This thesis addresses one such field of research namely, micromachined resonator based filters and introduces a novel design methodology by providing an overall ease and simplification during the design flow. Present day filter applications are both bulky and off chip. An alternative, in the form of surface micromachined filters, which introduces considerable size reduction, exhibits industry-standard Quality factors and provide on chip capability, is studied and expanded upon. The aim of this study is twice fold, one to allow the designers a method to design second order filters with greater flexibility than offered by hitherto standards and established procedures; two, to suggest an instructive guideline for extending the design process for higher order filters. The thesis also lays the foundation for fabrication of micromachined filters with mask fabrication, bill of materials, and processing experiments. It furthermore addresses the practical issues and constraints, such as aging, noise, and stability etc., which plague the transition of these research based prototypes to working systems

Doctor of Philosophy

dissertationThis thesis presents the design, fabrication and characterization of a microelectromechanical system (MEMS) based complete wireless microsystem for brain interfacing, with very high quality factor and low power consumption. Components of the neuron sensing system include TiW fixed-fixed bridge resonator, MEMS oscillator based action-potential-to-RF module, and high-efficiency RF coil link for power and data transmissions. First, TiW fixed-fixed bridge resonator on glass substrate was fabricated and characterized, with resonance frequency of 100 - 500 kHz, and a quality factor up to 2,000 inside 10 mT vacuum. The effect of surface conditions on resonator's quality factor was studied with 10s of nm Al2O3 layer deposition with ALD (atomic layer deposition). It was found that MEMS resonator's quality factor decreased with increasing surface roughness. Second, action-potential-to-RF module was realized with MEMS oscillator based on TiW bridge resonator. Oscillation signal with frequency of 442 kHz and phase noise of -84.75 dBc/Hz at 1 kHz offset was obtained. DC biasing of the MEMS oscillator was modulated with neural signal so that the output RF waveform carries the neural signal information. Third, high-efficiency RF coil link for power and data communications was designed and realized. Based on the coupled mode theory (CMT), intermediate resonance coil was introduced and increased voltage transfer efficiency by up to 5 times. Finally, a complete neural interfacing system was demonstrated with board-level integration. The system consists of both internal and external systems, with wireless powering, wireless data transfer, artificial neuron signal generation, neural signal modulation and demodulation, and computer interface displaying restored neuron signal

Frequency Tunable Magnetostatic Wave Filters With Zero Static Power Magnetic Biasing Circuitry

A single tunable filter can reduce the complexity, loss, and size when compared to switchable filter banks and enable new applications. Although magnetostatic wave tunable filters offer broad and continuous frequency tuning and high-quality factor (Q-factor), they consume high power and require large electromagnets to alter the magnetostatic wave velocity for filter frequency tuning. Here, we demonstrate miniature and high selectivity magnetostatic wave tunable filters with zero static power realized in Yttrium Iron Garnet thin films. The center frequency can be tuned via current pulses applied to a magnetic bias assembly from 3.36 GHz to 11.09 GHz with an insertion loss of 3.2 dB to 5.1 dB and out-of-band third order input intercept point (IIP3) of 41 to 44 dBm. Overall, the adaptability, wide frequency tuning range, and zero static power consumption of the tunable filter position it as a critical technology, effectively addressing challenges in broadband ADCs, RF transceivers, broadband digital phased array antennas, and interference mitigation in 5G and 6G networks. Broadly frequency tunable, high selectivity filters open new avenues for more efficient and dynamic RF front ends, ensuring optimal performance and seamless communication in the ever-evolving landscape of modern wireless technologies.Comment: The main manuscript contains 6918 words and 5 figures comprising 15 panels in total. The supplementary document consists of 14 Supplementary Notes and 30 Supplementary Figure