A MEMS BPSK demodulator: Micromechanical Mixing and Filtering using MetalMUMPs

Purpose The purpose of this paper is to investigate the feasibility of using micro electromechanical systems (MEMS) to convert a binary phase shift keying (BPSK) signal to a simpler amplitude shift keying (ASK) scheme. Design/methodology/approach The prototype is designed within the SOIMUMPs® fabrication process constraints. The fabrication constraints imposed geometric limitations on what could be tested. These constraints were used to build a mathematical model, which in turn was used to optimize the response using MATLAB®. The optimized design was tested using finite element analysis with CoventorWare®, and finally lab tests on the fabricated device were performed to confirm theoretical predictions. Findings Theoretical predictions compared well with lab measurements on a prototype device measuring 2.9 mm2. The prototype was tested with a carrier frequency of 174 kHz at a BPSK data rate of 3 kHz and carrier amplitude of 6 V. With these parameters, ASK modulation indices of 0.96 and 0.94 were measured at the two output sensors. Originality/value This study provides a MEMS solution for BPSK to ASK conversion. The study also identifies what limits betterment of the modulation index and data rate. Such a device has potential application in wireless sensor network (WSN) nodes that have energy harvesters and sensors that are also built in MEMS. Being a MEMS device, it can facilitate integration in such WSN nodes and, hence, potentially reduce size and costs.

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“…BPSK detection in MEMS is described in Scerri et al (2013). A BPSK to ASK converter is generally used as a first step to digital detection.…”

Section: Background and Literaturementioning

confidence: 99%

A MEMS BPSK to ASK converter

Scerri

Portelli

Grech

et al. 2019

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“…x Conclusions: In region 1, the device can be used as a filter and/or a mixer or even as a binary phase shift keying demodulator [6]. The operation in region 2 has potential for applications involving a random number generation (RNG) for crypto systems [7] and also as the chaotic carrier generators for secure communications [8].…”

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confidence: 99%

Versatility provided by electrostatic torsional microstructure as consequence of its complex dynamics

et al. 2014

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The results presented show that a simple microstructure involving a plate supported by two tethers can exhibit varied dynamics due to its nonlinearities. The plate vibrates such that the tethers experience a torsional twisting and it is designed within the constraints imposed by the MetalMUMPs process. Each region of operation has different applications and one can traverse through these regions by adjusting the sensing and actuation voltages. As one would expect, the nonlinearities dominate at higher voltages, with the first signs of chaotic trajectories appearing at 75 V. Parameters of the nonlinear model are first determined from finite-element analysis responses, and results from subsequent numerical simulations for each region are presented. Introduction:The drive to increase the functionality in portable devices is always increasing and one way of providing increased functionality is by having structures that can be applied for different applications. The MEMS device presented here is one such structure. Having a good mathematical model is instrumental in accurate prediction of the different modes of operation. Modelling of the dynamics of MEMS resonators is extensively covered in the literature [1][2][3][4]. Numerical solutions that involve distributed models and finite-element analysis (FEA) provide the best description of system behaviour, but are computationally expensive. Assumptions are taken to develop nonlinear systems of equations that are able to give a good enough approximation. It is common to ignore all modes of vibration and keep the most prominent one. Further assumptions are taken on modelling the spring behaviour. A linear, quadratic and cubic spring stiffness term is considered in [1], whereas in [2] only the linear and cubic terms are included. The inhomogeneity of the silicon structure and geometric nonlinearities are often responsible for this behaviour [1]. When it comes to damping, the behaviour is more complex. Damping can be divided into two categories: thermoelastic effects and fluid damping. The dominant form of damping is determined by the Knudsen number [5]. In [5], the nonlinear relationship between the viscous damping coefficient, gap and pressure is clearly seen, especially for gaps less than 800 nm. However, in much of the reviewed literature related to resonators with gaps larger than 800 nm, the effects of damping are assumed to be captured by a viscous damping coefficient.This Letter first presents the mathematical model of the structure and the parameters determined from the FEA simulations. Then, different regions of behaviour are identified from the nonlinear model. In the final Section, applications related to each region are discussed.

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