Abstract
The large ring laser gyroscope is a high-precision angular velocity inertial sensor for Earth-rotation monitoring and autonomous time determination. However, its beat-frequency signal is often weak and susceptible to scattering noise, thermal noise, electronic interference and environmental disturbances, leading to a limitation on the signal-to-noise ratio(SNR) of conventional single-channel detection. This paper proposes a four-channel coherent fusion algorithm for beat signals with approximately 45 ° phase spacing, in which a phase-projection model is established and closed-form in-phase and quadrature fusion expressions are derived. Theoretical analysis shows that, under ideal amplitude balance, exact 45 ° phase spacing, and independent identically distributed channel noise, the proposed method provides an approximately 3 dB SNR improvement over single-channel detection. MATLAB simulation and real beat-frequency measurements from a 400 mm large ring laser gyroscope are conducted for validation. The simulation results show an SNR improvement close to the theoretical value. In the real gyroscope experiment, the average SNR of the four original channels was 32.3123 dB, while the fused I- and Q-channel SNRs reached 35.6502 dB and 34.9782 dB, corresponding to improvements of 3.3379 dB and 2.6659 dB, respectively. The average improvement of the two fused outputs was approximately 3.0019 dB, which is consistent with the theoretical prediction. The proposed algorithm has low computational complexity and is suitable for real-time implementation in multi-channel beat-signal detection systems.