Force feedback linearization for higher-order electromechanical sigma-delta modulators.
Abstract A higher-order electromechanical sigma-delta modulator can greatly improve the signal-to-noise ratio compared with a second-order loop that only uses the sensing element as a loop filter. However, the electrostatic force feedback on the proof mass is inherently nonlinear, which will produce...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
2006.
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| Subjects: | |
| Online Access: | Get fulltext |
| Summary: | Abstract A higher-order electromechanical sigma-delta modulator can greatly improve the signal-to-noise ratio compared with a second-order loop that only uses the sensing element as a loop filter. However, the electrostatic force feedback on the proof mass is inherently nonlinear, which will produce harmonics in the output spectrum and limits the total signal-to-noise and distortion ratio. High performance inertial sensors, which use sigma-delta modulators as a closed-loop control system, have strict requirements on the output signal distortion. In this paper, nonlinear effects from the force feedback and pick-off circuits are analysed and a strategy for force feedback linearization is put forward which can considerably improve the signal-to-noise and distortion ratio. A PCB prototype of a fifth-order electromechanical modulator with a bulk micromachined accelerometer was used to demonstrate the concept. |
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