Papers by Keyword: Signal Demodulation

Abstract: Among all the kinds of optical fiber sensors, FBG and LPFG become the main current owing to its features and advantages. LPFG sensor is especially suitable in high temperature sensing and stimulates more related research interests. The key point of LPFG sensing is the signal demodulation and processing. In this paper, signal demodulation of the LPFG strain sensor was studied based on Arrayed Waveguide Grating. The fabrication method and high temperature performance of this sensor were presented,and a novel strain signal demodulation method was presented based on Arrayed Waveguide Grating (AWG) device by equi-intensity cantilever beam. The experimental results demonstrated that the signal demodulation technology based on AWG has many advantages, such as simple structure, innovative and reliable performance.

Abstract: Nonlinear acoustics deals with various nonlinear effects that occur in ultrasonic wave propagation. The method is suitable for material characterisation, as it uses different nonlinear phenomena associated with material imperfections. The method has been used for detecting nonlinearities in cracked solids by: measuring distortions of acoustic signals, estimating resonance frequency shifts or assessing nonlinear vibro-acosutic modulations. The latter is the most widely used non-classical approach to probe material nonlinearities. The method involves vibro-acoustic interactions of ultrasonic wave and modal vibration in damaged specimens. Modulation intensity that strongly relates to damage severity - is usually assessed in the frequency domain and often leads to confusing results when large modulations are involved. The paper investigates the time domain analysis of vibro-acoustic modulated signals. Several methods for instantaneous frequency calculation used to assess the intensity of modulation - are compared. Simulated and experimental data are used in these investigations.

Abstract: Non-driven structure silicon micromechanical gyroscope can sense rolling, pitching and yaw angular rate of the rotating body at the same time, which is suitable for rotating body gesture detection. But this characteristic is not suitable for non-rotating flight carrier. So this study uses micro motor to provide spin angular velocity for non-driven silicon micromechanical gyroscope, and to further generate gyroscopic effect which is sensitive to the attitude information, including rolling rate, yaw angular rate and pitch angular rate of low-speed rotating or non-rotating object. The study analyses the output signals based on simulation rotating object experiments of three-axis moving of silicon micromechanical gyroscope, the study uses phase based method to determine deflection polarity, and uses double accelerometer multiplication algorithm to demodulate the output signals of gyro. All above results provide a basis research results for further realize the goal of real-time demodulation of gyro signals when silicon micromechanical gyroscope is applied to the non-rotating and rotating flight carrier.

Abstract: In order to improve measurement accuracy of all fiber-optical current transformer (FOCT), an improved demodulation algorithm was proposed for a sine modulation. The formula for effective phase modulation depth (EPMD) was firstly presented, and three kinds of potential external disturbance in EPMD were analyzed. To overcome the current measurement error induced by these EPMD disturbances, we put forward an improved algorithm for time-dependent measurement of EPMD by second- and fourth-order harmonic component of optoelectronic signal. A simulation experiment in different disturbance intensity were carried out, and the results showed that when measured current is between 200A~1500A,the proposed algorithm can enhance the current measurement accuracy by over 30 times than the conventional algorithm, and measurement relative deviation can be maintained below 0.2% if the disturbance intensity is below 5%.

Abstract: We report a silicon micro-machined gyroscope without the driven conformation. The output signal of the gyroscope contains the rolling, yawing, and pitching angular rates information. The principle of signal generation of the gyroscope is described with the equation, and the demodulation method of the gyroscope signals is illustrated by the experimental evidences. Toward the end, the key performances of the gyroscope are also presented.