Chirp signal analysis with amplitude modulation

2012 ◽  
Author(s):  
Gheorghe Gavriloaia ◽  
Catalin Neamtu ◽  
Mariuca-Roxana Gavriloaia
Keyword(s):  
Amplitude Modulation ◽  
Signal Analysis ◽  
Chirp Signal

scholarly journals Coherent Pulse-Compression Lidar Based on 90-Degree Optical Hybrid

Sensors ◽  
2019 ◽  
Vol 19 (20) ◽  
pp. 4570 ◽  
Author(s):  
Jing Yang ◽  
Bin Zhao ◽  
Bo Liu
Keyword(s):  
Phase Difference ◽  
Amplitude Modulation ◽  
Detection Probability ◽  
Pulse Compression ◽  
Random Phase ◽  
Local Oscillator ◽  
Chirp Signal ◽  
Lidar System ◽  
Coherent Pulse

A coherent pulse-compression lidar system based on a 90-degree optical hybrid is demonstrated in this paper. In amplitude modulation (AM) mode, the returned RF chirp signal will be influenced by a random phase difference between local oscillator and echo light, causing fluctuations in the ranging results, and as a result the detection probability is small. By using the 90-degree optical hybrid, two orthogonal complementary signals are obtained to stabilize the result so as to increase the detection probability. We performed an experiment to measure the distance of a white printed wall which is about 65 m away from the system. The detection probability increased from 65% to 99.88%, and the precision is improved from 0.42 m to 0.27 m.

scholarly journals Planetary Gearbox Fault Diagnosis via Torsional Vibration Signal Analysis in Resonance Region

2017 ◽  
Vol 2017 ◽  
pp. 1-18 ◽  
Author(s):  
Kangqiang Li ◽  
Zhipeng Feng ◽  
Xihui Liang
Keyword(s):  
Fault Diagnosis ◽  
Resonance Frequency ◽  
Amplitude Modulation ◽  
Torsional Vibration ◽  
Signal Analysis ◽  
Resonance Region ◽  
Torsional Vibrations ◽  
Explicit Equation ◽  
Planetary Gearbox ◽  
Time Frequency

Planetary gearbox torsional vibration signals are free from the extra amplitude modulation effect due to time-varying transmission paths and have simpler frequency structure than translational ones. Gear faults result in modulation on the torsional resonance vibration and are manifested by the modulation feature. These merits are exploited for planetary gearbox fault diagnosis in this paper. Gear fault induced torsional vibrations in resonance region are modelled as amplitude modulation and frequency modulation (AM-FM) processes, the explicit equation of Fourier spectrum is derived, and the sideband characteristics are summarized. To avoid complex sideband analysis, amplitude and frequency demodulation analysis methods are exploited. The equations of amplitude and frequency demodulated spectra are derived in closed form, and their frequency structures are revealed. For fault diagnosis based on above theoretical derivations, a resonance frequency identification approach is proposed through time-frequency analysis of torsional vibrations during variable speed processes, according to the independence nature of resonance frequency on running conditions. The theoretical derivations and proposed approach are illustrated by numerical simulated signal analysis and are further validated through dynamics modelling and lab experimental tests. Localized faults on the sun, planet, and ring gears are successfully diagnosed.

A Fault Detection Approach Based on Sound Signal Analysis for Equipment Monitoring

2020 ◽  
pp. 129-139
Author(s):  
Weihai Sun ◽  
Lemei Han
Keyword(s):  
Fault Detection ◽  
Signal Analysis ◽  
Energy Analysis ◽  
Detection Method ◽  
Sound Signal ◽  
Practical Significance ◽  
Time Frequency ◽  
Detection Approach ◽  
Machine Fault ◽  
Learning Data

Machine fault detection has great practical significance. Compared with the detection method that requires external sensors, the detection of machine fault by sound signal does not need to destroy its structure. The current popular audio-based fault detection often needs a lot of learning data and complex learning process, and needs the support of known fault database. The fault detection method based on audio proposed in this paper only needs to ensure that the machine works normally in the first second. Through the correlation coefficient calculation, energy analysis, EMD and other methods to carry out time-frequency analysis of the subsequent collected sound signals, we can detect whether the machine has fault.

Synthesis of 16 Quadrature Amplitude Modulation Using Polarization-Multiplexing QPSK Modulator

2011 ◽  
Vol E94-B (7) ◽  
pp. 1809-1814 ◽  
Author(s):  
Isao MOROHASHI ◽  
Takahide SAKAMOTO ◽  
Masaaki SUDO ◽  
Atsushi KANNO ◽  
Akito CHIBA ◽  
...  
Keyword(s):  
Amplitude Modulation ◽  
Quadrature Amplitude Modulation ◽  
Polarization Multiplexing
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