Research on pulse stretching of underwater bubbles echo signal of lidar

The simulated PM-spectrum fractal sea surfaces and the 3-D near-field distributed model of horn antenna are built, the near-field formulas of KA method are deduced. The near-field scattering coefficient and the Doppler echo signal of rough sea surfaces are calculated, the agreement with measured data proved the correctness and validity of the near-field scattering model.

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An Inverse Synthetic Aperture Ladar Imaging Algorithm of Maneuvering Target Based on Integral Cubic Phase Function-Fractional Fourier Transform

Electronics ◽

10.3390/electronics7080148 ◽

2018 ◽

Vol 7 (8) ◽

pp. 148 ◽

Cited By ~ 4

Author(s):

Yakun Lv ◽

Yanhong Wu ◽

Hongyan Wang ◽

Lei Qiu ◽

Jiawei Jiang ◽

...

Keyword(s):

Fourier Transform ◽

Phase Function ◽

Fractional Fourier Transform ◽

Doppler Frequency ◽

Synthetic Aperture ◽

Cubic Phase ◽

Echo Signal ◽

Imaging Algorithm ◽

Maneuvering Target ◽

Cubic Phase Function

When imaging maneuvering targets with inverse synthetic aperture ladar (ISAL), dispersion and Doppler frequency time-variation exist in the range and cross-range echo signal, respectively. To solve this problem, an ISAL imaging algorithm based on integral cubic phase function-fractional Fourier transform (ICPF-FRFT) is proposed in this paper. The accurate ISAL echo signal model is established for a space maneuvering target that quickly approximates the uniform acceleration motion. On this basis, the chirp rate of the echo signal is quickly estimated by using the ICPF algorithm, which uses the non-uniform fast Fourier transform (NUFFT) method for fast calculations. At the best rotation angle, the range compression is realized by FRFT and the range dispersion is eliminated. After motion compensation, separation imaging of strong and weak scattering points is realized by using ICPF-FRFT and CLEAN technique and the azimuth defocusing problem is solved. The effectiveness of the proposed method is verified by a simulation experiment of an aircraft scattering point model and real data.

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Research of Wavelet Packet Analysis in the De-Noising of Ultrasonic Echo Signal

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.403-408.1817 ◽

2011 ◽

Vol 403-408 ◽

pp. 1817-1822

Author(s):

Xi Feng Zhou ◽

Xiao Wu ◽

Qian Gang Guo

Keyword(s):

Signal To Noise Ratio ◽

Wavelet Packet ◽

Random Noise ◽

Flaw Detection ◽

Low Frequency ◽

Local Analysis ◽

Echo Signal ◽

Wavelet Packet Analysis ◽

Ultrasonic Flaw

The quality of ultrasonic flaw echo signal is the foundation of achieving qualitative and quantitative analysis in the in ultrasonic flaw detection. In practice, the flaw echo signals are often contaminated or even annihilation by random noise. According to the characteristics of ultrasonic flaw echo signal, wavelet packet has more accurate local analysis ability in low frequency and high frequency part. This paper discusses de-noising in ultrasonic signals based on wavelet packet analysis, and proposes an improved threshold approach for de-noising. The results show that: It remarkably raises the signal-to-noise ratio of ultrasonic flaw echo signal and improves the quality of signal with improved wavelet packet threshold.

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Effect of Pumping Pulse Duration on Echo Signal Amplitude in Four-Pulse PELDOR

Applied Magnetic Resonance ◽

10.1007/s00723-011-0232-6 ◽

2011 ◽

Vol 41 (1) ◽

pp. 59-67 ◽

Cited By ~ 17

Author(s):

A. D. Milov ◽

Yuriy A. Grishin ◽

S. A. Dzuba ◽

Yu. D. Tsvetkov

Keyword(s):

Pulse Duration ◽

Signal Amplitude ◽

Echo Signal

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