Design of a Digitalized Microgyroscope System Using <inline-formula> <tex-math notation="LaTeX">$\Sigma \Delta $ </tex-math></inline-formula> Modulation Technology

Abstract

This paper presents a digitalized gyroscope system using ΣΔ modulation on ADC and DAC sections. Both discrete ADC and DAC chips are replaced with these ΣΔ sections. The ΣΔ ADC technology can convert signals between analog and digital domain using analog modulators on the PCB(Printed Circuit Board) circuit with different amplifiers and matched capacity couples and digital backend processing in Field Programmable Gate Array (FPGA). While the ΣΔ ADC technology are easily realized in FPGA by signal processing algorithms, the major sections of the digital system such as auto-gain control(AGC) and PLL(phase-lock loop) are also implemented in FPGA, which have provided the programmable flexibility of the whole system. The signal to noise ratio (SNR) of power spectrum density (PSD) and stability in both ΣΔ ADC and ΣΔ DAC are analyzed, respectively. Considering the sections of the ΣΔ ADC and DAC woks in different clock domain, the frequency characteristics of each section should be analyzed. In the drive mode of the gyroscope, the force feedback is applied through the direct bitstream of the modulator. To evaluate the gyroscope vibration stability of the ΣΔ modulation based system, the Leeson-model phase noise characteristics of the drive mode detection signal are in-depth theoretically calculated with different parameters including the noise models and the circuit components, which has been experimentally validated by the measured PSD analysis. Finally, the performance evaluation of the whole gyroscope system is demonstrated by time domain sampling and Allan variance analysis. 1 The digitalized system achieved a scale factor of 94LSB/°/s, with a linearity of 83.1 ppm, noise of , bandwidth is 75Hz and the bias instability is 2.94°/hr.

A New Design of an MOEMS Gyroscope Based on a WGM Microdisk Resonator

“…Based on results we have previously published [14,15], the optimized parameters of the disk resonator are shown in Table 2. The frequency split and Q value of the resonator are 13 Hz and 90,000.…”