A constrained minimum power adaptive beamformer with time‐varying adaptation rate

Geophysics ◽  
1979 ◽  
Vol 44 (6) ◽  
pp. 1088-1096 ◽  
Author(s):  
Wen‐Wu Shen
Keyword(s):  
Adaptive Algorithm ◽  
Detection System ◽  
Signal To Noise Ratio ◽  
High Amplitude ◽  
Research Station ◽  
Power Performance ◽  
Signal To Noise ◽  
Filter Output ◽  
Short Period ◽  
Noise Ratio

A linear adaptive algorithm was developed for array beamforming purposes. The design goal for the algorithm is to minimize the squared filter output subject to filter constraints which allow energy propagating from the array steering direction to pass without being distorted. The adaptive filter coefficients were initialized to satisfy the constraints which were preserved during the iterations. The adaptation rate is inversely varied with filter output and total input channel power. Performance of the algorithm was studied using the recorded short‐period array data from the Korean Seismic Research Station. Processed were a high‐amplitude signal from Kamchatka, a medium‐amplitude signal from eastern Kazakh, and a number of low‐amplitude signals from central Eurasia. Results of signal‐to‐noise ratio gain relative to a conventional beamformer among the events tested were consistent and were in the range of 4.5 to 6.5 dB in the wide passband. Much better signal‐to‐noise ratio improvement was obtained in the low‐frequency passband. The adaptive algorithm was programmed in the real‐time mode and can be implemented in a front‐end detection system.

Quantitative Analysis of Noise Impact on Duffing Chaotic Detection System Using Lyapunov Characteristic Exponents

2011 ◽  
Vol 130-134 ◽  
pp. 1331-1337
Author(s):  
Wen Jing Hu ◽  
Zhi Zhen Liu ◽  
Zhi Hui Li
Keyword(s):  
Detection System ◽  
Signal To Noise Ratio ◽  
Duffing Oscillator ◽  
Threshold Value ◽  
System State ◽  
Signal To Noise ◽  
Phase Trajectories ◽  
Lyapunov Characteristic Exponents ◽  
Noise Ratio ◽  
System States

Performance of the Duffing oscillator to detect weak signals buried in heavy noise is analyzed quantitatively by LCEs. First in the case of noise, differential equations to compute LCE s are derived using RHR algorithm, so the quantitative criteria to identify system states are obtained. Then using LCEs, the threshold value of the forced periodic term is found accurately. Finally the system state and state change are analyzed using LCEs by keeping the threshold value and varying the noise intensity, and the minimum signal to noise ratio is determined. By contrast of phase trajectories and LCEs, it shows that phase trajectories disturbed by strong noise sometimes are ambiguous to our eyes, but through LCEs, the system state can be identified clearly and quantitatively especially in strong noise background. So the minimum signal to noise ratio can be obtained accurately.

Télémètre à détection coherente avec un laser CO2 à ondes entretenues : étude et conception

1983 ◽  
Vol 61 (2) ◽  
pp. 318-331 ◽  
Author(s):  
Denis Vincent ◽  
Gabriel Otis
Keyword(s):  
Detection System ◽  
Signal To Noise Ratio ◽  
Optical Power ◽  
Experimental System ◽  
Intermediate Frequency ◽  
Local Oscillator ◽  
Heterodyne Detection ◽  
Signal To Noise ◽  
Noise Ratio ◽  
Rotating Target

We performed a theoretical and experimental study of a 10.6 μm heterodyne detection system with nonlinear postdetection. A single laser serves as both transmitter and local oscillator; the intermediate frequency is given by the Doppler effect due to a rotating target. An electrooptic crystal modulates the amplitude of the laser beam at a frequency of 15 kHz; a synchronous voltmeter measures the return signal after the nonlinear element. Values of the signal-to-noise ratio with respect to incident optical power agree with the results of the theoretical model. In particular, experimentally measured target-induced frequency spreading effects on the signal-to-noise ratio correspond to the predictions of the model. We also describe an experimental system.

Symmetrical short-period and high signal-to-noise ratio heterodyne grating interferometer

2015 ◽  
Vol 13 (10) ◽  
pp. 100501-100505 ◽  
Author(s):  
Cunbao Lin Cunbao Lin ◽  
Shuhua Yan Shuhua Yan ◽  
Zhiguang Du Zhiguang Du ◽  
Guochao Wang Guochao Wang ◽  
Chunhua Wei Chunhua Wei
Keyword(s):  
Signal To Noise Ratio ◽  
High Signal ◽  
Signal To Noise ◽  
Short Period ◽  
Grating Interferometer ◽  
Noise Ratio

scholarly journals Detection Spectrum Optimization of Stealth Aircraft Targets From a Space-based Infrared Platform

2021 ◽  
Author(s):  
Xinyue Ni ◽  
Shutian Yu ◽  
Xiaofeng Su ◽  
Fansheng Chen
Keyword(s):  
Detection System ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
Central Wavelength ◽  
Detection Techniques ◽  
Detection Systems ◽  
Spectrum Detection ◽  
Detection Technology ◽  
Spectrum Optimization ◽  
Noise Ratio

Abstract Advances in infrared detection techniques require novel spectrum dynamic-modification strategies capable of sensing unprecedentedly low target radiant intensities. A conventional fixed-spectrum detection system cannot satisfy the effective detection of stealth aircraft targets due to complex Earth background clutter and atmospheric attenuation. Therefore, a detection method that can highlight aircraft targets is urgently needed to enhance stealth aircraft detectability. In this research, a spectrum set consisting of different bandwidths associated with a central wavelength is established. Furthermore, a signal-to-noise ratio of the stealth aircraft is computed using the established spectrum set. Finally, the optimal spectrum is selected according to the maximal signal-to-noise ratio from the spectrum set. Our numerical experiments and simulations further demonstrate that the proposed methodology can substantially strengthen the detection performance of stealth aircraft compared with traditional fixed-spectrum detection systems. This work on detection spectrum optimization paves the way to stealth aircraft detection and opens new vistas in the field of target detection technology.

scholarly journals Leak Detection in Plastic Water Supply Pipes with a High Signal-to-Noise Ratio Accelerometer

2018 ◽  
Vol 51 (1-2) ◽  
pp. 27-37 ◽  
Author(s):  
Konstantinos Marmarokopos ◽  
Dimitrios Doukakis ◽  
George Frantziskonis ◽  
Markos Avlonitis
Keyword(s):  
Water Supply ◽  
Wave Attenuation ◽  
Detection System ◽  
Signal To Noise Ratio ◽  
Leak Detection ◽  
Small Distance ◽  
High Signal ◽  
Vibration Frequencies ◽  
Signal To Noise ◽  
Noise Ratio

A method for detecting leaks in plastic water supply pipes through analysis of the pipe’s surface vibration using a high signal-to-noise ratio accelerometer is proposed and examined. The method involves identification of the changes in vibration frequencies caused on the pipe by the leak and is developed from and examined with respect to detailed experiments. The results are promising, showing that leak detection in plastic pipes is possible provided that the sensor is placed at a small distance from the leak, since wave attenuation in plastic is strong. The results indicate that the methodology has the potential to be a new and competitive type of mobile leak detection system.

Catenary image denoising method using lifting wavelet-based contourlet transform with cycle shift-invariance

2019 ◽  
Vol 17 (01) ◽  
pp. 1850060 ◽  
Author(s):  
Changdong Wu ◽  
Hua Jiang
Keyword(s):  
Image Denoising ◽  
Mean Squared Error ◽  
Detection System ◽  
Signal To Noise Ratio ◽  
Contourlet Transform ◽  
Signal To Noise ◽  
Denoising Method ◽  
Shift Invariance ◽  
Lifting Wavelet ◽  
Noise Ratio

In the catenary status detection system based on the image processing, quality of the captured catenary image is critical. In order to obtain a high quality image for further analysis, this paper proposes a new catenary image denoising method based on lifting wavelet-based contourlet transform with cycle shift-invariance (LWBCTCS). In this method, the lifting wavelet is first constructed based on wavelet transform (WT). Then, to decrease the redundancy of contourlet transform (CT), the lifting wavelet-based contourlet transform (LWBCT) is built by using the lifting wavelet to replace the Laplacian pyramid (LP) transform of CT. Finally, the LWBCT with the cycle shift-invariance (LWBCTCS) algorithm is combined to reduce the pseudo-Gibbs phenomena of LWBCT. The proposed method not only has the virtues of multi-scale and multi-direction, but also reduces the visual artifacts in the denoised image. The results of comparative experiments with captured catenary image show that the proposed method can achieve satisfactory denoising performance, in particular, for catenary image with abundant texture and detail outline information. It not only eliminates noise but also preserves the textures and details simultaneously. Besides, comprehensive consideration of the denoising performance shows that the proposed algorithm in terms of the signal-to-noise ratio (SNR), peak signal-to-noise ratio (PSNR) and mean squared error (MSE) is stable than those conventional denoising algorithms, including WT, CT, curvelet transform (CV) and BLS-GSM methods. The visual quality as well as quantitative metrics is superior than those conventional denoising methods.

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