Gyroscope Technology and Applications: A Review in the Industrial Perspective <s> Micro-Electro-Mechanical System (MEMS) Gyroscopes <s> A monolithic silicon gyroscope is described which is completely batch fabricated on a silicon wafer. Only one side of the wafer is employed so the process is readily adaptable to any size wafer. The gimbals, flexures, and electrodes are all made on the same substrate so that a mass-producible instrument is realized. The process is compatible with the use of on-chip electronics, which will be required to maximize the performance of the instrument. The authors describe several methods of incorporating the electrodes within the device substrate. They enumerate the advantages of the monolithic construction, and mention potential areas of application. Initial test data showed a noise-limited rate detection capability of 4 deg/s at a 1-Hz bandwidth. > <s> BIB001 </s> Gyroscope Technology and Applications: A Review in the Industrial Perspective <s> Micro-Electro-Mechanical System (MEMS) Gyroscopes <s> Abstract In this paper we investigate the behaviour of a silicon-based angular rate sensor which uses a cantilever beam for the vibrating mass. To this end, we examine how the mechanical quality factor influences both the sensitivity and stability of the sensor in the absence of any feedback control. By way of analysis, a simple physical model is presented that describes both the relationship between the tuned device and its sensitivity and, also, how the stability of the device is affected by the various modes of the beam's vibration. <s> BIB002 </s> Gyroscope Technology and Applications: A Review in the Industrial Perspective <s> Micro-Electro-Mechanical System (MEMS) Gyroscopes <s> Silicon micromechanical gyro performance has progressed to the threshold of useful initial applications, at least 1 deg/s. The vibrating wheel on a gimbal (VWOG) is a new gyro design with the promise of improved manufacturability. With a variety of accelerometers from which to choose, the advent of the silicon gyro begins the era of silicon micromechanical inertial guidance. <s> BIB003 </s> Gyroscope Technology and Applications: A Review in the Industrial Perspective <s> Micro-Electro-Mechanical System (MEMS) Gyroscopes <s> Since micromachining technology hs raised the prospect of fabricating high performance sensors without the associated high cost and large size, many researchers have investigated micromachined rate gyroscopes. The vast majority of research has focused on single input axis rate gyroscopes, but this paper presents work on a dual input axis micromachined rate gyroscope. The key to successful simultaneous dual axis operation is the quad symmetry of the circular oscillating rotor design. Untuned gyroscopes with mismatched modes yielded random walk as low as 10/spl deg///spl radic/(Hour) with cross axis sensitivity ranging from 3% to 16%. Subsequent mode frequency matching via electrostatic tuning allowed performance of 2/spl deg///spl radic/(Hour), but at the expense of excessive cross axis sensitivity. <s> BIB004 </s> Gyroscope Technology and Applications: A Review in the Industrial Perspective <s> Micro-Electro-Mechanical System (MEMS) Gyroscopes <s> This paper presents a review of silicon micromachined accelerometers and gyroscopes. Following a brief introduction to their operating principles and specifications, various device structures, fabrication, technologies, device designs, packaging, and interface electronics issues, along with the present status in the commercialization of micromachined inertial sensors, are discussed. Inertial sensors have seen a steady improvement in their performance, and today, microaccelerometers can resolve accelerations in the micro-g range, while the performance of gyroscopes has improved by a factor of 10/spl times/ every two years during the past eight years. This impressive drive to higher performance, lower cost, greater functionality, higher levels of integration, and higher volume will continue as new fabrication, circuit, and packaging techniques are developed to meet the ever increasing demand for inertial sensors. <s> BIB005 </s> Gyroscope Technology and Applications: A Review in the Industrial Perspective <s> Micro-Electro-Mechanical System (MEMS) Gyroscopes <s> We investigated the mechanical coupling between the drive and detection modes of micromachined vibrating rate gyroscopes, and designed and fabricated a gyroscope with a new structure to reduce the coupling. The coupling of the oscillator was measured using a new measurement system with a two-dimensional laser displacement meter. The oscillations were found to have an elliptical motion due to the coupling. When the frequency mismatch was reduced by means of electrostatic frequency tuning with a DC bias voltage, the coupling increased. The new structure, which has independent beams for the drive and detection modes, exhibited weaker coupling; and the resolution was 0.07 deg/sec at a bandwidth of 10 Hz. <s> BIB006 </s> Gyroscope Technology and Applications: A Review in the Industrial Perspective <s> Micro-Electro-Mechanical System (MEMS) Gyroscopes <s> We describe the principle of operation and experimental characterization of an integrated micromechanical vibratory rate gyroscope based on resonant sensing of the Coriolis force. The new design has several advantages over rate gyroscopes that utilize open-loop displacement sensing for rotation rate measurement. Some of these advantages include simpler dynamics and control, improved scale factor stability, large dynamic range, high resolution, and a quasi-digital FM output. A z-axis integrated surface-micromachined gyroscope fabricated at the Sandia National Laboratories has a measured noise floor of 0.3 deg/sec//spl radic/(Hz). <s> BIB007 </s> Gyroscope Technology and Applications: A Review in the Industrial Perspective <s> Micro-Electro-Mechanical System (MEMS) Gyroscopes <s> Microelectromechanical ~MEMS! gyroscopes have wide-ranging applications including automotive and consumer electronics markets. Among them, complementary metal-oxide semiconductor-compatible MEMS gyroscopes enable integration of signal condition- ing circuitry, multiaxis integration, small size, and low cost. This paper reviews various designs and fabrication processes for integrated MEMS gyroscopes and compares their performance. Operational principles and design issues of MEMS vibratory gyroscopes are also addressed. <s> BIB008 </s> Gyroscope Technology and Applications: A Review in the Industrial Perspective <s> Micro-Electro-Mechanical System (MEMS) Gyroscopes <s> This paper presents the perfect matched-mode operation of a type I non-degenerate z-axis tuning-fork gyroscope (i.e., 0 Hz frequency split between high-Q drive and sense modes). The matched-mode tuning fork gyroscope (M2-TFG) is fabricated on 50-µ m thick SOI substrate and displays an overall rate sensitivity of 24.2 mV/o/s. Allan Variance analysis of the mode-matched device demonstrates an angle random walk (ARW) of 0.045 o/√ hr and a measured bias instability of 0.96 o/hr. Temperature characterization of the M2-TFG verifies that mode matching is maintained over a temperature range of 20-100 ° C. <s> BIB009 </s> Gyroscope Technology and Applications: A Review in the Industrial Perspective <s> Micro-Electro-Mechanical System (MEMS) Gyroscopes <s> ·In this paper, the design, implementation and characterization of a continuous time transimpedance-based ASIC for the actuation and sensing of a high-Q MEMS tuning fork gyroscope (TFG) is presented. A T-network transimpedance amplifier (TIA) is used as the front-end for low-noise, sub-atto-Farad capacitive detection. The T-network TIA provides on-chip transimpedance gains of up to 25 MΩ, has a measured capacitive resolution of 0.02 aF/√ Hz at 15 kHz, a wide dynamic range of 104 dB in a bandwidth of 10 Hz and consumes 400 μW of power. The CMOS interface ASIC uses this TIA as the front-end to sustain electromechanical oscillations in a MEMS TFG with motional impedance greater than 10 MΩ. The TFG interfaced with the ASIC yields a two-chip angular rate sensor with measured rate noise floor of2.7°/hr/√Hz, bias instability of 1°/hr and rate sensitivity of 2 mV/°/s. The IC is fabricated in a 0.6-μm standard CMOS process with an area of 2.25 mm 2 and consumes 15 mW. <s> BIB010 </s> Gyroscope Technology and Applications: A Review in the Industrial Perspective <s> Micro-Electro-Mechanical System (MEMS) Gyroscopes <s> In this paper, we report on the design, fabrication, and characterization of an in-plane mode-matched tuning-fork gyroscope (M2-TFG). The M2-TFG uses two high-quality-factor (Q) resonant flexural modes of a single crystalline silicon mi- crostructure to detect angular rate about the normal axis. Operating the device under mode-matched condition, i.e., zero-hertz frequency split between drive and sense modes, enables a Q -factor mechanical amplification in the rate sensitivity and also improves the overall noise floor and bias stability of the device. The M2 -TFG is fabricated on a silicon-on-insulator substrate using a combination of device and handle-layer silicon etching that precludes the need for any release openings on the proof-mass, thereby maximizing the mass per unit area. Experimental data indicate subdegree-per-hour Brownian noise floor with a measured Allan deviation bias instability of 0.15deg /hr for a 60-mum-thick 1.5 mm X 1.7 mm footprint M2-TFG prototype. The gyroscope exhibits an open-loop rate sensitivity of approximately 83 mV/deg/s in vacuum. [2007-0100]. <s> BIB011 </s> Gyroscope Technology and Applications: A Review in the Industrial Perspective <s> Micro-Electro-Mechanical System (MEMS) Gyroscopes <s> This paper reports, for the first time, a vibratory MEMS z-axis rate gyroscope architecture with structurally forced anti-phase drive-mode and linearly coupled, dynamically balanced anti-phase sense-mode. The new design utilizes two symmetrically-decoupled tines with drive- and sense-mode synchronization mechanisms, and prioritizes sense-mode quality factor. The levered drive-mode mechanism structurally forces the anti-phase drive-mode motion and eliminates the lower frequency spurious modes. The linearly coupled, dynamically balanced antiphase sense-mode design minimizes substrate energy dissipation. SOI prototypes characterized in vacuum demon-strated drive-mode quality factor of 67,000 and ultra-high sense-mode quality factor of 125,000, yielding mechanical scale factor of 0.4 nm/(°/h) for mode-matched operation. <s> BIB012 </s> Gyroscope Technology and Applications: A Review in the Industrial Perspective <s> Micro-Electro-Mechanical System (MEMS) Gyroscopes <s> This paper reports on the design, fabrication, and testing of a multiple-beam tuning-fork gyroscope featuring high Quality factors (Q). A multiple-beam tuning-fork structure is designed to achieve high Qs in its drive mode and sense mode. The gyroscope is fabricated on a 30μm-thick SOI wafer using a one-mask fabrication process. The measured Qs of the fabricated gyroscope are 162,060 in the drive-mode and 85,168 in the sense mode at an operation frequency of 16.8kHz. Under a frequency split of 6Hz, the prototype device demonstrates a rate sensitivity of 0.02mV/°/sec.Copyright © 2009 by ASME <s> BIB013 </s> Gyroscope Technology and Applications: A Review in the Industrial Perspective <s> Micro-Electro-Mechanical System (MEMS) Gyroscopes <s> Resonator micro optic gyro (RMOG) with a waveguide-type ring resonator is a promising candidate for applications requiring small, light and robust gyros. In optical passive ring resonator gyros, clockwise (CW) and counter clockwise (CCW) lightwaves are phase-modulated at different frequencies to reduce the backscattering induced noise. The effectiveness of this technique, however, is determined by the carrier suppression level. In this paper, the influence of the carrier suppression level on the gyro performance is examined experimentally for an RMOG system with a silica waveguide resonator. In our experiment, carrier suppression is applied onto both the CW and the CCW lightwaves at the same time to achieve higher total suppression. We show that carrier suppression as high as 100 dB can be achieved by optimizing the amplitude of the phase modulation. A bias stability of 0.46 /s in 50 seconds is demonstrated in an RMOG with a silica waveguide ring resonator having a ring length of 7.9 cm. This is the best result reported to date, to the best of our knowledge, for waveguide-type ring resonator gyros of this size. <s> BIB014 </s> Gyroscope Technology and Applications: A Review in the Industrial Perspective <s> Micro-Electro-Mechanical System (MEMS) Gyroscopes <s> Abstract This paper reports a new dual mass vibratory MEMS z-axis rate gyroscope architecture that prioritizes the sense-mode quality factor and provides improved ordering of the mechanical vibrational modes. The proposed linearly coupled, dynamically balanced anti-phase sense-mode design minimizes substrate energy dissipation to maximize the quality factor. The levered drive-mode mechanism structurally forces the anti-phase drive-mode motion of the symmetrically decoupled tines eliminating the lower frequency spurious mode and providing true mechanical rejection of external shocks and accelerations. SOI prototypes were characterized in a vacuum chamber demonstrating drive-mode quality factor of 67,000 and ultra-high sense-mode quality factor of 125,000. A vacuum packaging technology was introduced and demonstrated a ceramic package-level sealed gyroscope with a quality factor on the order of 100,000. The high quality factor and mode ordering of the new design provide a path toward ultra-high scale factor without compromising the sensitivity to external accelerations. <s> BIB015 </s> Gyroscope Technology and Applications: A Review in the Industrial Perspective <s> Micro-Electro-Mechanical System (MEMS) Gyroscopes <s> This study developed a microelectromechanical systems (MEMS) doubly decoupled gyroscope with a wide driving frequency range. The gyroscope increases the resonance bandwidths of both the drive and sense oscillators without sacrificing their Q factors. This bandwidth enhancement ensures good frequency matching between the drive and sense oscillators even if fabrication imperfections are present. Additionally, no in-operation frequency tuning mechanism is needed. The gyroscope can be driven at any frequency within the overlapping region of the resonance bands of the drive and sense oscillators. Experiments showed that the gyroscope driving voltage can be of any frequency within a ~240-Hz bandwidth. The wide bandwidth provides flexibility and ease of use. The device is fabricated by the MetalMUMPs process developed by MEMSCAP, Inc. Its doubly decoupled structure minimizes the interference/coupling between the drive and sense units. Performance tests under rotation rates equal to or smaller than 18.71 rad/s showed that the gyroscope has a sensitivity of 4.28 mV/(rad/s). <s> BIB016 </s> Gyroscope Technology and Applications: A Review in the Industrial Perspective <s> Micro-Electro-Mechanical System (MEMS) Gyroscopes <s> A low-noise low-delay digital signal processor is constructed on a single field-programmable gate array. An equivalent input noise as low as 3.752 nV/√Hz is demonstrated for the digital signal processor, which can detect an equivalent Sagnac effect of 0.003°/s in a resonant micro optic gyro (RMOG) with a 2.5-cm diameter ring resonator. With the processing time reduced from hundreds of seconds to 1.1 μs , this processor significantly increases the loop gain of the feedback loop and reduces the reciprocal noise in the RMOG. Owing to the fast speed of this processor, the lock-in frequency accuracy is reduced to 0.78 Hz (1σ), which is equivalent to a rotation rate of 0.004°/s. Relationship between this digitalized RMOG output signal and angular rate is obtained from ±0.25°/s to ±400°/s. The standard deviation of the residuals between RMOG output results and linear fit curve is 0.0236°/s. <s> BIB017 </s> Gyroscope Technology and Applications: A Review in the Industrial Perspective <s> Micro-Electro-Mechanical System (MEMS) Gyroscopes <s> Resonator micro-optic gyro (RMOG) is a promising candidate for the next generation inertial rotation sensor based on the Sagnac effect. A current modulation technique used in an external cavity laser diode is proposed to construct the gyroscope system for the first time. The resonance curves before and after eliminating accompanying amplitude modulation are theoretically analyzed, calculated, and simulated; the demodulation curves with different modulation currents are formulated theoretically; and the optimum modulation current corresponding to the maximum sensitivity is obtained. The experiment results from the established RMOG experimental setup demonstrate that a bias stability of 2.7 deg/s (10 s integrated time) over 600 s, and dynamic range of ±500 deg/s are demonstrated in an RMOG with a silica optical waveguide ring resonator having a ring length of 12.8 cm. <s> BIB018 </s> Gyroscope Technology and Applications: A Review in the Industrial Perspective <s> Micro-Electro-Mechanical System (MEMS) Gyroscopes <s> This review surveys micromachined gyroscope structure and circuitry technology. The principle of micromachined gyroscopes is first introduced. Then, different kinds of MEMS gyroscope structures, materials and fabrication technologies are illustrated. Micromachined gyroscopes are mainly categorized into micromachined vibrating gyroscopes (MVGs), piezoelectric vibrating gyroscopes (PVGs), surface acoustic wave (SAW) gyroscopes, bulk acoustic wave (BAW) gyroscopes, micromachined electrostatically suspended gyroscopes (MESGs), magnetically suspended gyroscopes (MSGs), micro fiber optic gyroscopes (MFOGs), micro fluid gyroscopes (MFGs), micro atom gyroscopes (MAGs), and special micromachined gyroscopes. Next, the control electronics of micromachined gyroscopes are analyzed. The control circuits are categorized into typical circuitry and special circuitry technologies. The typical circuitry technologies include typical analog circuitry and digital circuitry, while the special circuitry consists of sigma delta, mode matching, temperature/quadrature compensation and novel special technologies. Finally, the characteristics of various typical gyroscopes and their development tendency are discussed and investigated in detail. <s> BIB019 </s> Gyroscope Technology and Applications: A Review in the Industrial Perspective <s> Micro-Electro-Mechanical System (MEMS) Gyroscopes <s> Micro-electromechenical Systems (MEMS) gyroscope is widely used in many occasions to measure the angular speed of the moving objects and attracts the attentions of many research institutions all over the world. This kind of sensor possesses the advantages of high degree of integration, low cost and consumption of power. This paper first introduces the research development of silicon MEMS gyroscope since eighties of last century; the researches of many institutions such as Draper Laboratory and UC Berkeley are mentioned and different design principles, control methods and structures are presented. This review then presents the key theories and technologies of the sensor and some research results of them. In additional, some recent new applications of MEMS gyroscope are also been introduced in this paper such as wearable motion capture system and micro inertial measurement unit. Finally, according to the review, some views of silicon MEMS gyroscope and its future prospects are put forwarded. <s> BIB020 </s> Gyroscope Technology and Applications: A Review in the Industrial Perspective <s> Micro-Electro-Mechanical System (MEMS) Gyroscopes <s> In this paper, we consider a technique for increasing the aspect ratio (AR) of an electrostatic comb drive structure of a microelectromechanical system, which is fabricated with the bulk microstructuring technology. The technical solution is described, which allows increasing the electrical capacity of driving and measuring comb structures, reducing the duration of plasma etching and increasing AR of various MEMS devices. The novel design of the comb drive improves the diffusion of the active plasma components into the dedicated cavities. This leads to an increase of the maximum achievable etching depth while maintaining a minimum gap between the teeth in the order of one micrometer. <s> BIB021
MEMS gyroscopes generally use a vibrating mechanical element as a sensing element for detecting the angular velocity. They do not have rotating parts that require bearings and this allows an easy miniaturization and the use of the manufacturing techniques typical of MEMS devices. All MEMS gyroscopes with vibrating element are based on the transfer of energy between two vibration modes caused by the acceleration of Coriolis. The Coriolis acceleration, proportional to the angular velocity, is an apparent acceleration that is observed in a rotating frame of reference. To better understand the concept, we can consider a particle of mass m moving in space with a velocity v (See Figure 9a) . integrating optical waveguides leads to even smaller solutions. Thus, RMOG is a promising candidate for applications requiring small, light and robust gyros. In RMOGs, clockwise and counter-clockwise waves are phase-modulated at different frequencies to reduce backscattering induced noise. The effectiveness of this technique, however, is determined by the carrier suppression level. In the experiment reported in BIB014 , carrier suppression is applied onto both the CW and the CCW waves at the same time to achieve higher total suppression. Ma et al. obtained a bias stability of 0.46°/s over 50 s with a silica waveguide ring resonator, having a ring length of 7.9 cm. In 2013, a 2.5 cm diameter ring was equipped with a low-noise, low-delay digital signal processor based on FPGA BIB017 , reaching a 0.67°/s bias stability over 3600 s. The proposed solution can detect a minimum rotation rate of 0.25°/s. In the same year, Lei et al. BIB018 proposed a current modulation technique in an external cavity laser diode to construct a gyroscope system for the first time. The experimental results from the established RMOG setup demonstrate a bias stability of 2.7°/s (over 600 s) with a silica optical waveguide ring resonator having a ring length of 12.8 cm. MEMS gyroscopes generally use a vibrating mechanical element as a sensing element for detecting the angular velocity. They do not have rotating parts that require bearings and this allows an easy miniaturization and the use of the manufacturing techniques typical of MEMS devices. All MEMS gyroscopes with vibrating element are based on the transfer of energy between two vibration modes caused by the acceleration of Coriolis. The Coriolis acceleration, proportional to the angular velocity, is an apparent acceleration that is observed in a rotating frame of reference. To better understand the concept, we can consider a particle of mass m moving in space with a velocity v (See Figure 9a) ). Once fixed to the reference system in Figure 9a , if it is rotating with an angular velocity Ω = Ωxi (with i the unitary vector along the x axis) around the x axis, an observer, solidly anchored to the z axis, sees the particle moving along the z axis with a Coriolis acceleration equal to ac = 2v × Ω, although a real force is not applied along the z axis. This is the key physical principle of the vibrating mass MEMS gyroscope, described like a mass-spring system (see Figure 9b) . The vibrating mass MEMS gyroscope has two orthogonal mechanical excitation modes along which the mass can move. If ky and kz are the elastic stiffness parameters proper of the frame, while cx and cy are the respective damping coefficients, the master equations result to be BIB008 : Once fixed to the reference system in Figure 9a , if it is rotating with an angular velocity Ω = Ω x i (with i the unitary vector along the x axis) around the x axis, an observer, solidly anchored to the z axis, sees the particle moving along the z axis with a Coriolis acceleration equal to a c = 2v × Ω, although a real force is not applied along the z axis. This is the key physical principle of the vibrating mass MEMS gyroscope, described like a mass-spring system (see Figure 9b) . The vibrating mass MEMS gyroscope has two orthogonal mechanical excitation modes along which the mass can move. If k y and k z are the elastic stiffness parameters proper of the frame, while c x and c y are the respective damping coefficients, the master equations result to be BIB008 : The primary mode is excited along y (drive axis) by applying a force F Drive (see Equation (19)), while the secondary mode along x (sense axis) is excited by the Coriolis force F z (see Equation (20)). By knowing the mode drive axis mode, the displacement along the z axis is proportional only to the angular velocity Ω = Ω x i. Moreover, being Q y/z and ω y/z the quality factor and the resonance frequency of the driving mode (x) and the sensing mode, respectively, the displacement of the mass m along z assumes the following expression BIB002 : As expressed in Equation (22), the MEMS gyroscope sensitivity can be improved by matching the resonant frequencies ω y and ω z , and by reduction of friction (e.g., by creating an under vacuum operating environment) in order to improve the quality factor Q y/z . Based on these physical principles, a brief panoramic of the research development of silicon MEMS gyroscope that were designed, prototyped and realized from the late 1980s to the 1990s. The following listed sensors are based on revealing Coriolis force and represent, someway, the milestone in the roadmap of MEMS gyro technology improvement. The pioneering work to miniaturize inertial systems, made by Draper Laboratory (expert in inertial guidance systems for military and space applications), led to the creation of MEMS gyros and accelerometers as we know today. In the late 1980s, they developed a hand-assembled device to prove the feasibility of a silicon gyro. In the following work, they also successfully constructed a monolithic double gimbal gyro with a rate detection capability of 4 • /s at a 1 Hz bandwidth; this performance was limited by noise BIB001 . Until 1996, in Draper Laboratory, other structures were designed to improve performance with an even simpler fabrication process. A planar design of a gyro based on the tuning fork principle was then presented. It was equipped with the comb drive mechanism developed at UC Berkeley, which showed a rate capability of about 0.1 • /s in a 60 Hz bandwidth. Afterwards, they explored the fabrication advantages of the vibrating wheel on a gimbal-based gyro design capable of a better rate sensing BIB005 BIB003 . Several researches, aimed to integrate part of control and signal processing on chip, to develop dual-axis gyroscope and to improve fabrication and performance with multi degree of freedom design, were made at UC Berkeley during next years. In 1996, Clark, Howe, and Horowitz presented a z-axis vibratory rate gyroscope. This device integrated with a trans-resistance amplifier while the sense mode offers a differential measurement using interdigitated comb fingers. This device has a resolution of 1 • /s/ √ Hz improvable to 0.1 • /s/ √ Hz in a second generation. After that, Juneau, Pisano and Smith reported a surface-micromachined dual-axis gyroscope based on a rotor disk that can equally sense rotation about two orthogonal axes. This device, integrated with some electronics, showed a random walk of 10 • / √ h and a cross-axis sensitivity comprised between 3% and 16%  BIB004 BIB020 BIB006 BIB007 . In 1999, Mochida, Tamura and Ohwada (Murata, Yokohama R&D Center) reported two designs of micromachined gyroscopes: a simple structure used as a reference, and another one with independent beams for drive and detection modes, thus uncoupling drive and sense mode for improving resolution. They characterized the two devices through laser meter equipment to observe displacements and the overall behavior, so they found that the gyroscope with independent beams had a resolution of 0.07 • /s at a bandwidth of 10 Hz, even if limited by increased noise at resonance, caused by oscillation instability. This performance resulted to be better than that related to the reference device, due to weak coupling between the two modes BIB006 . Further development followed since the late 1990s, thanks to the fact that silicon technology became more mature, so it was possible to integrate control and processing electronic components into MEMS. Studies aiming at improving MEMS gyroscopes increased, being already known the main aspects of theory and operation; the availability of more sophisticate test equipment to characterize prototypes, more powerful design tools and industrial interest in other application fields (at consumer level) contributed to the progress of this technology. Georgia Institute of Technology also put great efforts in the research of MEMS gyroscopes. In this institution, the Matched-Mode Tuning Fork Gyroscope (M2-TFG) BIB009 BIB010 BIB011 BIB019 was developed in 2006 by Zaman et al. It used an electrostatic comb drive to move the proof-masses in x-axis and a capacitive detecting in y-axis to sense rotation in z-axis. Drive and sense mode were electrostatically balanced to achieve perfect mode matching; this design improved sensitivity, bias stability and noise floor. at University of California developed at first the design of a z-axis MEMS gyroscope based on a tuning fork, then a new dual-mass vibratory MEMS z-axis rate gyroscope that improved the mechanical vibratory modes. These structures forced an anti-phase drive-mode and a linearly-coupled dynamically-balanced anti-phase sense-mode, that prioritizes sense-mode quality factor. The prototypes were characterized in a vacuum chamber, demonstrating a quality factor drive-mode of 67,000 and of 125,000 for the sense-mode BIB012 BIB015 . Meanwhile, the joined forces of Old Dominion University and University of Utah led to the improvement of the M2-TFG architecture. In fact, Wang et al. presented a multiple beam tuning fork gyroscope that reached a measured Q-factor of 255,000 for drive-mode and 103,000 for sense-mode at 15.7 kHz. Further measurements pointed out a rate resolution of 0.37 • /h/ √ Hz, a rate sensitivity of 80 VPP/ • /s while ARW and bias instability were 6.67 • / √ h and 95 • /h, respectively BIB013 . Other researches were performed towards enabling a wider bandwidth to expand flexibility and ease of use. Thus, in 2012, Tsai et al. developed a doubly decoupled MEMS gyroscope to minimize coupling between the drive-mode and sense-mode, which used frequencies in a 240 Hz bandwidth BIB016 . Finally, the report by BIB021 about a MEMS gyro characterized by a comb-shaped drive with enlarged capacity gradient considered the aspect ratio or the wavy aspect ratio of the comb drive as a fundamental key to improve performance BIB021 .