Higher Order Noise-Shaping Filters for High-Performance Micromachined Accelerometers

Southampton Univ., Southampton
IEEE Transactions on Instrumentation and Measurement (Impact Factor: 1.79). 11/2007; 56(5):1666 - 1674. DOI: 10.1109/TIM.2007.904477
Source: IEEE Xplore


Micromachined inertial sensors that have been incorporated in sigma-delta force-feedback loops have been proven to improve linearity, dynamic range, and bandwidth, and also provide a direct digital output. Previous work mainly focused on using the sensing element only to form a second-order single-loop sigma-delta modulator (SigmaDeltaM); however, the advantages of higher order single-loop electromechanical SigmaDeltaM have not been fully explored. High-performance inertial sensors require higher signal-to-quantization noise ratio (SQNR). This paper presents topologies for higher order single-loop electromechanical SigmaDeltaM with optimal stable coefficients that lead to a better SQNR. The topologies have good immunity to fabrication tolerances, which was verified by Monte Carlo analysis. The topologies are applicable not only to accelerometers but also to other inertial sensors such as gyroscopes.

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    • "Capacitive accelerometers, operating as electromechanical delta-sigma loops, have gained increasing popularity. Implementations of this type of sensor interfaces have been introduced in, for example, [2] [3], whereas recent analysis concerning higher order noise shaping is presented in [4]. A common feature of most published delta-sigma interfaces is the use of a low-Q mechanical element. "
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    ABSTRACT: A continuous-time accelerometer interface is feasible when a high dynamic range together with a wide signal band is required. In this paper the implementation of a continuous-time force-feedback loop for a capacitive sensor element with a full-scale signal of ±1.5 g is presented. The interface is measured to attain a noise equivalent acceleration (NEA) density of 500 at 30 Hz for the on-chip digitized output and 300 at 30 Hz for the analog output using a capacitive half-bridge sensor element with a single pair of electrodes. The essential circuit structures of the closed-loop sensor will be presented and analyzed in detail.
    Preview · Article · Aug 2009 · Sensors and Actuators A Physical
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    • ". Schematic diagram of a capacitive accelerometer [16] We use the high-performance capacitive accelerometer schematically shown in Fig. 3, considered also in [17], [18], [16]. The lumped parameters of the bulk-micro-machined accelerometer sensing element are summarized in Table I. "
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    ABSTRACT: High-performance micro-electro-mechanical systems (MEMS) sensors can be implemented by incorporating a micro-machined capacitive sensing element in a Sigma-Delta-Modulators force-feedback loop, forming an electro-mechanical Sigma-Delta Modulator (EM-SDM). We propose a transfer-function based design methodology to realize discrete- and continuous-time low-pass EM-SDM. The design is performed at the level of the integrated system consisting of the electro-mechanical sensor and of the electronic circuit; we call this the dynamics-level. We also illustrate a technique to perform the conversion of the discrete-time design to a continuous-time one. The approach is demonstrated through an EM-SDM design example for a bulk micro-machined, capacitive accelerometer.
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    ABSTRACT: This paper presents a single-electrode capacitive sensor using a single-bit second-order incremental delta–sigma architecture. In order to achieve high accuracy in this capacitance-to-digital converter (CDC), the shielding signal and the digitally controlled offset capacitors are used in combination with the delta–sigma CDC. The designed sensor is suitable for capacitive transducers for ±10 pF input range with sub-fF resolution.
    No preview · Article · Aug 2013 · Analog Integrated Circuits and Signal Processing
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