To address the issues of quadrature component attenuation and signal-to-noise ratio (SNR) degradation caused by carrier phase delay in Phase-Generated Carrier (PGC) demodulation, this paper proposes a phase delay compensation method based on sampling-point shift pre-calibration. By establishing a discrete phase offset model, we derive the mathematical relationship between sampling point shift and carrier cycle duration, and introduce a compensation mechanism that adjusts the starting point of the sampling sequence to achieve carrier phase pre-alignment. Theoretical analysis demonstrates that this method restricts the residual phase error to within Δθ_max = πf₀/f_s, thereby fundamentally avoiding the denominator-zero problem inherent in traditional compensation algorithms when θ approaches 45°. Experimental validation using an Extrinsic Fabry–Perot Interferometric (EFPI) ultrasonic sensor shows that, at a sampling rate of 10 MS/s, the proposed pre-alignment algorithm improves the minimum demodulation SNR by 35 dB and reduces phase fluctuation error to 2% of that of conventional methods. Notably, in 1100 consecutive measurements, the proposed method eliminates demodulation failures at critical phase points (e.g., π/4, π/2), which are commonly problematic in traditional techniques. By performing phase pre-compensation at the signal acquisition level, this method significantly enhances the long-term measurement stability of interferometric fiber-optic sensors in complex environments while maintaining the existing PGC demodulation architecture.

This paper addresses the suppression of multi-frequency line spectrum vibrations during the operation of indoor substations through the development of an active vibration isolation scheme based on a piezoelectric stack inertial actuator. Based on the finite element modal analysis, the excitation frequencies that strongly influence structural response were identified, and the excitation points and sensor layout strategies were determined under a collocated control configuration. Subsequently, the actuator’s structural design and system integration were carried out. Experimental results demonstrate vibration amplitude reductions of 18.75 dB at 100 Hz, 46.02 dB at 200 Hz, and 32.04 dB at 300 Hz, respectively, validating the effectiveness of the proposed method in controlling line spectrum vibrations at multiple frequencies. The study shows that the coordinated optimization of modal matching and the dynamic response capability of inertial actuators provides experimental evidence and technical guidelines for active vibration isolation in large plate-shell structures.

The proliferation of urban substations situated near residential areas has intensified the need for effective noise control, particularly in the mid-to-high frequency range. Traditional sound barriers often rely on mass-increasing strategies, which are constrained by the mass law and practical installation limitations. This study investigates a lightweight sound barrier solution utilizing an embedded Acoustic Black Hole (ABH) structure to address this challenge. Numerical simulations predict a significant improvement in the Sound Transmission Loss (STL) of the ABH plate compared to uniform plates. Experimental validation conducted in a specific cavity setup demonstrates that the damped ABH plate (2.97 mm thick, 3.47 kg) achieves a superior noise reduction performance, matching or even exceeding that of a significantly heavier uniform plate (4 mm thick, 5.00 kg) above its characteristic frequency (254 Hz), while realizing a 30% weight reduction. The superior performance is explained by two synergistic mechanisms: the ABH’s power-law profile concentrates bending wave energy for highly efficient damping at the thin tip; it compresses the structural wavelength, reducing radiation efficiency synchronously. The findings confirm the ABH structure as a promising, lightweight technology for controlling substation equipment noise, with broad application prospects in urban acoustic environmental protection.

In this study, a phase-generated carrier (PGC) demodulation algorithm combined with the extended Kalman filter (EKF) algorithm based on an electro-optic modulator (EOM) is proposed, which can achieve nonlinear distortion (such as modulation depth drift and carrier phase delay) suppression for high-frequency phase carrier modulation. The improved algorithm is implemented on a field-programmable gate array (FPGA) hardware platform. The experimental results by the PGC-EKF method show that total harmonic distortion (THD) decreases from −32.61 to −54.51 dB, and SINAD increases from 32.59 to 47.86 dB, compared to the traditional PGC-Arctan method. This indicates that the PGC-EKF demodulation algorithm proposed in this paper can be widely used in many important fields such as hydrophone, transformer, and ultrasound signal detection.