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21 pages, 2022 KiB

Open AccessArticle

An Analysis of Noise in Multi-Bit ΣΔ Modulators with Low-Frequency Input Signals

by Pablo Vera, Andreas Wiesbauer and Susana Paton

Sensors 2022, 22(19), 7458; https://doi.org/10.3390/s22197458 - 1 Oct 2022

Viewed by 2099

Digital and smart sensors are commonly implemented using multi-bit

Σ Δ

Digital and smart sensors are commonly implemented using multi-bit

Σ Δ

Modulators. Undesired signals can be present at the ADC input, such as low-frequency signals with medium or high amplitude, as a consequence of mechanical artifacts in the MEMS and/or temporary signal overload. Simulations and measurements of those sensors with such signals show temporary increments of in-band noise power. This paper investigates the factors that produce this transient performance loss. Interestingly, noise increments happen when the modulator is forced to toggle between three adjacent levels and is not correlated with the typical tonal behavior of

Σ Δ

Modulators. Hence, the sensor performance is sensitive to some specific input patterns even if tonal behavior is decreased by dithering the input of the ADC. Different error sources, such as the mismatch between DAC cells, loop filter linearity error, and quantization error, contribute to the observed noise increments. Our aim is to analyze each of these error sources to understand and quantify in-band noise power increments, and to desensitize the ADC from the undesired input patterns. Some estimation equations are proposed and verified through extensive simulations, by means of deterministic and stochastic methods. These equations are influenced by some modulator parameters and can be used to optimize them in order to reduce such in-band noise power increments. Full article

(This article belongs to the Section Intelligent Sensors)

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15 pages, 12088 KiB

Open AccessArticle

3-Bit Digital-to-Analog Converter with Mechanical Amplifier for Binary Encoded Large Displacements

by Lisa Schmitt, Philip Schmitt and Martin Hoffmann

Actuators 2021, 10(8), 182; https://doi.org/10.3390/act10080182 - 4 Aug 2021

Cited by 13 | Viewed by 3975

Abstract

We present the design, fabrication, and characterization of a MEMS-based 3-bit Digital-to-Analog Converter (DAC) that allows the generation of large displacements. The DAC consists of electrostatic bending-plate actuators that are connected to a mechanical amplifier (mechAMP), enabling the amplification of the DAC output displacement. Based on a parallel binary-encoded voltage signal, the output displacement of the system can be controlled in an arbitrary order. Considering the system design, we present a simplified analytic model, which was confirmed by FE simulation results. The fabricated systems showed a total stroke of approx. 149.5 ± 0.3 µm and a linear stepwise displacement of 3 bit correlated to 2³ ≙ eight defined positions at a control voltage of 60 V. The minimum switching time between two input binary states is 0.1 ms. We present the experimental characterization of the system and the DAC and derive the influence of the mechAMP on the functionality of the DAC. Furthermore, the resonant behavior and the switching speed of the system are analyzed. By changing the electrode activation sequence, 27 defined positions are achieved upgrading the 3-bit systems into a 3-tri-state (3³) system. Full article

(This article belongs to the Special Issue Cooperative Microactuator Systems)

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5 pages, 1079 KiB

Open AccessProceeding Paper

A Micromechanical Binary Counter with MEMS-Based Digital-to-Analog Converter

by Philip Schmitt, Hannes Mehner and Martin Hoffmann

Proceedings 2018, 2(13), 807; https://doi.org/10.3390/proceedings2130807 - 21 Nov 2018

Cited by 4 | Viewed by 2143

Abstract

Autonomous sensors are of interest in all cases where a continuous power source is not available or difficult to realize. Besides harvesting of electrical energy for a complex storage system, it is of interest to directly store an event in a non-electrical storage, but in a way that allows a later electrical read-out. Therefore, a miniaturized micromechanical binary counter is presented, which enables counting of threshold events, such as exceeding temperature limits or high mechanical shocks. An electro-mechanical digital-to-analog converter integrated in the binary counter is demonstrated as an option for monolithic electrical read-out of the mechanically stored information. Full article

(This article belongs to the Proceedings of EUROSENSORS 2018)

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