Excess Loop Delay compensated Electro-Mechanical Bandpass Sigma-Delta Modulator for Gyroscopes

Abstract

This paper presents a new excess loop delay (ELD) compensated micro-electro-mechanical sigma-delta modulator (∑ΔM) incorporating a gyroscope in series with a second-order electrical bandpass filter. The bandpass filter is optimized for large ELDs and is realized in a feedforward structure. The ∑ΔM is implemented on a field programmable gate array (FPGA) emulating continuous-time (CT) behavior in order to investigate the ELD effect. The digital setup gives also maximum flexibility in testing and characterization of different structures in a fast and efficient way. Measurements show stable modulators, with ELDs of nearly one time period of the sampled system, achieving in-band noise (IBN) below -60 dBFS. This paper demonstrates that the stability of ∑Δ modulators with large ELDs can be ensured with the new ELD compensation technique.