A High-Performance Digital Interface Circuit for a High-Q Micro-Electromechanical System Accelerometer

Li, Xiangyu; Hu, Jianping; Liu, Xiaowei

doi:10.3390/mi9120675

Cited by 19 publications

(15 citation statements)

References 20 publications

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“…where m x is the proof mass; k x is a stiffness of the proof mass spring; ω r is a resonant frequency of the micromechanical transducer. Substituting Equations (8) and 9, Equation (4) can be rewritten as follows:…”

Section: Output Differential Frequency and Sensitivity Of The Frequenmentioning

confidence: 99%

“…In the voltage-based or charge-based SPD, these voltage fluctuations are significantly amplified by the high-gain amplifier. This requires an increase of the proof mass to minimize the noise-floor and expand the dynamic range R D [7,8,13]. In contrast to this, there is no amplifier in the open-loop frequency-based SPD ( Figure 2).…”

Section: Noise Floor and Dynamic Range Of The Frequency-based Accelermentioning

confidence: 99%

“…There are many kinds of transducers in present micromechanical accelerometers, such as capacitive, piezo-resistive, electromagnetic, optical, thermal convective, acoustic waves resonant, field emission, tunnel transducers and so on [6]. The micromechanical accelerometers with capacitive transducers are widely used due to relatively simple transducer structure, high-sensitivity, reliability, thermal stability, excellent linearity, resolution, bandwidth, good compatibility with integrated circuits technology, and consequently low cost [7][8][9][10][11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, the switching-capacitor charge-based technique is conventionally used in closed-loop SPD to effectively suppress flicker noise [19]. Therefore, voltage control closed-loop SPD are frequently used today especially for high-sensitivity and high accuracy MEMS accelerometers [8][9][10][11][12][13]. However, there are the following disadvantages of voltage control closed-loop signal processing devices:…”

Section: Introductionmentioning

confidence: 99%

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Highly Sensitive Signal Processing Devices for Capacitive Transducers of Micromechanical Accelerometers

et al. 2019

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In this paper, the principles of the open-loop frequency-based signal processing devices for capacitive MEMS accelerometers are used to develop three CMOS IP-core (Intellectual Property core) projects of highly sensitive signal processing devices with frequency output. Signal processing devices designed in accordance with the considered method form an output of rectangular pulses whose frequencies equal a difference of signal frequencies from two identical generators with micromechanical accelerometer capacitive transducers in their frequency control circuits. First, the analog project scheme uses two harmonic LC oscillators and an analog mixer to form an output rectangular-shape differential-frequency signal, the frequency of which is dependent on the measured acceleration. Second, the digital project is fully scalable for various CMOS-technologies due to oscillators of rectangular pulses and a digital mixer. Third, the mixed-signal project combines the advantages of the analog and digital projects. The signal processing device projects were developed, modeled and compared to comprehensively solve the problems of increasing sensitivity, dynamic range, noise immunity and resistance to destabilizing factors (e.g., to temperature changes).

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Section: Output Differential Frequency and Sensitivity Of The Frequenmentioning

confidence: 99%

Section: Noise Floor and Dynamic Range Of The Frequency-based Accelermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Highly Sensitive Signal Processing Devices for Capacitive Transducers of Micromechanical Accelerometers

et al. 2019

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“…In the most recent decade, the readout interface circuit for micro-electromechanical systems (MEMS) sensors has been evolving toward digitalization [1][2][3]. It is simple to realize the digitalization by cascading an A/D converter.…”

Section: Introductionmentioning

confidence: 99%

A Straightforward Approach for Synthesizing Electromechanical Sigma-Delta MEMS Accelerometers

Chen

Yin

et al. 2019

Sensors

Self Cite

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The EM-Σ∆ (electromechanical sigma-delta) approach is a concise and efficient way to realize the digital interface for micro-electromechanical systems (MEMS) accelerometers. However, including a fixed MEMS element makes the synthesizing of the EM-Σ∆ loop an intricate problem. The loop parameters of EM-Σ∆ can not be directly mapped from existing electrical Σ∆ modulator, and the synthesizing problem relies an experience-dependent trail-and-error procedure. In this paper, we provide a new point of view to consider the EM-Σ∆ loop. The EM-Σ∆ loop is analyzed in detail from aspects of the signal loop, displacement modulation path and digital quantization loop. By taking a separate consideration of the signal loop and quantization noise loop, the design strategy is made clear and straightforward. On this basis, a discrete-time PID (proportional integral differential) loop compensator is introduced which enhances the in-band loop gain and suppresses the displacement modulation path, and hence, achieves better performance in system linearity and stability. A fifth-order EM-Σ∆ accelerometer system was designed and fabricated using 0.35 µm CMOS-BCD technology. Based on proposed architecture and synthesizing procedure, the design effort was saved, and the in-band performance, linearity and stability were improved. A noise floor of 1 µg/ √ Hz, with a bandwidth 1 kHz and a dynamic range of 140 dB was achieved.Sensors 2020, 20, 91 2 of 17 processing. Moreover, the use of one-bit feedback linearizes the inherent second-order relationship between voltage and electrostatic force effectively [6-10]. Despite the advantages mentioned above, there are still obstacles for a simple implementation. The obstacles mainly come from the MEMS sensing element. Since the limited in-band gain is provided by the MEMS sensing element [11], the total in-band characteristic is degenerated compared to a purely electrical Σ∆ modulator [8]; thus, high-order modulation is inevitable. Meanwhile, in order to suppress the Brownian noise, the sensing element is typically packaged in a vacuum cavity [9,11], resulting a highly under-damped subsystem. Moreover, this second order section is fixed and the inside first-order node (which is velocity) is inaccessible for an electrical circuit [12]. These negative factors mixed together seriously aggravate the synthesizing of loop parameters, which is already a complicated problem for a purely electrical Σ∆ modulator.This problem can be divided into two aspects. First is the stabilization of the EM-Σ∆ loop. For an electrical Σ∆ loop, the proof of stability has not been rigorously established; approximate models and empirical observations are used for stability check [8,13]. The situation is worse for EM-Σ∆, since there is an unchangeable highly under-damped MEMS structure. For most researchers [7-9,14] the first thing is to degenerate this second order section into a first-order one by introducing an adjustable zero. Then, the traditional design strategy for electrical Σ∆ can be used. However, this approach will int...

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Small-size MEMS Accelerometer Encapsulated in Vacuum Using Sigma-Delta Modulation

Lima

Cabral

Kuhlmann

et al. 2020

2020 IEEE International Symposium on Inertial Sensors and Systems (INERTIAL)

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A vacuum encapsulated MEMS accelerometer using Sigma-Delta modulation is here presented. Three different modulation orders (second, third, and fourth) were implemented in a field-programable gate array (FPGA), enabling flexibility for tuning the loop parameters in real-time. Three devices were measured, and the results are in good agreement with simulations performed in Simulink. A noise figure of 123 μg/√Hz for a bandwidth of 400 Hz and a range of at least ±1 g was experimentally measured. A figure of merit considering device size and bandwidth is proposed, highlighting the relevance of the results for the current state of the art.

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A High-Performance Digital Interface Circuit for a High-Q Micro-Electromechanical System Accelerometer

Cited by 19 publications

References 20 publications

Highly Sensitive Signal Processing Devices for Capacitive Transducers of Micromechanical Accelerometers

Highly Sensitive Signal Processing Devices for Capacitive Transducers of Micromechanical Accelerometers

A Straightforward Approach for Synthesizing Electromechanical Sigma-Delta MEMS Accelerometers

Small-size MEMS Accelerometer Encapsulated in Vacuum Using Sigma-Delta Modulation

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