Advancing MEMS Technology with Quartz Sensors for Tactical Grade and Navigation Grade IMUs

 

EMCORE has a 40-year history in the development of its Quartz MEMS technology introducing the first tactical grade single-axis gyro and inertial measurement unit (IMU) utilizing quartz sensors with its SDD3000 gyro and SDI500 IMU, along with the smallest tactical INS/GPS with its SDN500.

 

MEMS technology is often associated with silicon, but Quartz MEMS, pioneered by Systron Donner Inertial which was acquired by EMCORE in 2019, has inherent properties enabling it to deliver significantly higher performance characteristics than silicon.

Fundamental Performance Limit Mechanical Thermal Noise

A_G – angular gain
A – drive mode amplitude
M – proof mass
K_B – Boltzmann constant
Q – Q-factor
w – sense mode frequency
Trusov A. et al., PLANS ‘14

 

Size and amplitude matters in determination of the fundamental performance limit of CVG (Coriolis Vibratory Gyroscopes) and this is where quartz technology excels over silicon.

> How EMCORE’s Quartz MEMS Gyro Sensors Work 

 

1. Superior piezoelectric effect to silicon allows for lower noise (random walk)

• • Gyro ARW: 0.0008°/√ hr Navigation Grade
  • Accel VRW: 0.3 mG/√ Hz Strategic Grade

2. Reference level stability over years (quartz was used as the time standard before atomic clocks)

• • Gyro bias: <0.5°/hr over 5 years – Tactical grade
  • Accel bias: <0.3 mG over 5 years – Tactical/High-End Tactical Grade

3. Low sensitivity to temperature effects over military range (-55°C to +90°C)
   (Quartz = ~ 50 ppm, Si = ~ 5000 ppm)

• • Gyro over military temperature
    • Bias: <0.2°/hr (rms) High-End Tactical Grade
    • SF: <50 ppm (rms) High-End Tactical Grade
  • Accel over military temperature
    • Bias: <25 mG (rms) Navigation Grade
    • SF: ~ 25 ppm (rms) Navigation Grade

These properties make quartz the ideal material for truly high-performance MEMS.

Quartz MEMS Gyroscope In-Run Performance

Quartz MEMS will always outperform silicon MEMS and EMCORE’s latest laboratory results utilizing a test SDI500 IMU have shown that EMCORE’s technology for quartz sensors achieves navigation grade performance.

Quartz MEMS Summary

EMCORE’s current production SDI500 Quartz MEMS IMU successfully meets the market needs in tactical grade systems at 1°/hr, 1 mg. However, with quartz being uniquely well suited as a micromachining substrate for inertial sensors due to its extreme stability over time and temperature characteristics, EMCORE has demonstrated proof of high-end tactical grade performance of ~0.1°/hr, 0.025 mg, and navigation grade performance 0.01°/hr, 0.01 mg for its Next-Gen products.

 

 

 

 

View the Video on EMCORE’s current navigation and inertial sensing offering including Quartz MEMS and FOG gyros, IMUs and INS products.

The Key Parameters Enabling EMCORE Closed-Loop FOG Technology to Excel Over Legacy Alternatives

 

EMCORE’s Fiber Optic Gyroscope (FOG) program had its genesis in 2005-2006 with establishment of its Lithium Niobate foundry leading to the development of its patented IOC (Integrated Optical Circuit) and transceiver in 2008. This unique IOC enables closed-loop designs of very high bandwidth and accuracy for short-term to full navigation-grade applications. Following the launch its first FOG component in 2009, EMCORE’s FOG program received multiple U.S. patents and has been qualified for several key military programs. EMCORE’s leadership in the development of highly-accurate defense and military grade FOGs has since paved the way for the development of even more accurate FOG-based components including the EN-300 IMU.

 

The Technical Edge: How EMCORE’s FOG Technology Differs from Legacy Fiber Optic Gyros

Typical legacy Fiber Optic Gyro construction has a large single light source and many discrete components including splitter, monitor diode, and isolator. This Increases number of splices which results in poor polarization control and poor bias performance.

Legacy Fiber Optic Gyro Construction

 

The consequences of these limitations in optics technology is decreased power efficiency of the overall system, lower signal-to-noise ratio (SNR) to each gyro and poor angle random walk (ARW).

EMCORE Closed-Loop FOG Architecture

EMCORE’s compact design combines its unique transceiver (Tx/Rx) and IOC, both designed in-house at its foundry, with fiber coil in a closed-loop architecture resulting in fewer fiber splices, which improves polarization control and eliminates wavelength shifts over temperature. The unique transceiver architecture combines light source, detector and optical circulator in compact butterfly package resulting in superior ARW performance where the circulator doubles signal and improves ARW by 50%.

Compared to open-loop designs, closed-loop gyro also delivers better scale factor (SF) linearity, dynamic range and bias performance, so closed-loop outperforms open-loop in all key performance parameters.

EMCORE FOG-Based IMU: EN-300

EMCORE’s closed-loop FOG technology is designed for fast, accurate navigation and gyrocompassing, and low noise line-of-sight stabilization and is the foundation of the company’s EN-300 FOG IMU designed for tactical to navigation-grade applications. The EN-300-3 model achieves bias in-run stability as low as 0.04 degree/hr with ARW of 0.015 degree/rt-hr. This is up to 2.5X better bias performance and 10X better ARW performance of legacy systems, in a form, fit, and function compatible replacement package.

EMCORE EN-300: 10X Better ARW

The following graph illustrates the measured ARW performance of the EN-300 compared to a leading competitor. The EN-300 is offered in three performance grades, -1 with ARW of 0.007 deg/rt-hr, -3 with ARW of 0.015 deg/rt-hr, and -5 with ARW 0.03 deg/rt-hr.

Fiber Optic Gyro Summary

EMCORE’s unique Tx/Rx design enables compact FOG design with minimal splices and higher optical power for better ARW and bias stability than the competing technologies. The company’s lithium niobate technology enables closed-loop FOG designs with better SF linearity, dynamic range, and overall performance than open loop technology. Its world-class in-house foundry strives for continuous improvement of the Tx/Rx and IOC design to develop next generation FOG technology at a more rapid pace than competitors.

Conclusion: EMCORE Inertial Sensors Span the High-Performance Market

 

EMCORE’s technical breakthroughs in MEMS and FOG technology provide a significant value proposition to system developers enabling higher precision than ever before in cost and SWaP-constrained applications including optical targeting and platform stabilization, weapons systems, north-finding and navigation systems, commercial aviation flight control, and more!

Contact EMCORE

For further information and specifications, visit us on the web Contact | EMCORE, call +1 866-234-4976, or e-mail: navigation-sales@emcore.com.

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Video header: EMCORE 

This page was produced by North Coast Media’s content marketing staff in collaboration with EMCORE. NCM Content Marketing connects marketers to audiences and delivers industry trends, business tips and product information. The GPS World editorial staff did not create this content.