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Sensors and Actuators A 115 (2004) 336350 Symmetrical and decoupled nickel microgyroscope
 

Summary: Sensors and Actuators A 115 (2004) 336350
Symmetrical and decoupled nickel microgyroscope
on insulating substrate
Said Emre Alper, Tayfun Akin
Department of Electrical and Electronics Engineering, Middle East Technical University, Ankara, Turkey
Received 22 October 2003; received in revised form 16 April 2004; accepted 24 April 2004
Available online 15 June 2004
Abstract
This paper presents a symmetrical and decoupled surface micromachined gyroscope fabricated by electroforming thick nickel on a glass
substrate. The symmetric structure allows matched resonant frequencies for the drive and sense vibration modes for improved sensitivity,
while the decoupled drive and sense oscillation modes prevents unstable operation due to mechanical coupling, resulting in a low zero-rate
output drift. The use of a glass substrate instead of a silicon substrate reduces noise due to the parasitic signal coupling by two orders
of magnitude, according to both simulation results in CoventorWare and measured results on fabricated devices. A capacitive interface
circuit which is fabricated in a 0.8 m CMOS process is hybrid connected to the gyroscope, where the circuit has an input capacitance
lower than 50 fF and a sensitivity of 33 mV/fF, which are currently limited by the parasitic capacitances due to hybrid wirebonding. It has
been identified that the amount of parasitic capacitances must be lower than or at least in the same order with the electrical equivalent
capacitance of the gyroscope for clear mechanical resonance characteristics to be obtained. Fabricated gyroscopes have close resonant
frequencies for the drive and sense modes, as 37.2 and 38.3 kHz, respectively. Calculations on measured resonance values suggest that the
fabricated gyroscope with 16 m-thick structural layer provides a Brownian noise floor of 7.3/h/Hz1/2 at vacuum. Currently, the overall
rate sensitivity of the gyroscope is limited to 96/h in 50 Hz bandwidth for matched-frequency operation, and it can be decreased down to

  

Source: Akin, Tayfun - Department of Electrical and Electronics Engineering, Middle East Technical University

 

Collections: Engineering