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Start Over Author "Liu, Aijun" Publisher institute of electrical and electronics engineers (ieee)
79 results on '"Liu, Aijun"'

11. Polarization quaternion DOA estimation based on vector MISC array

Author

Yu Changjun, Zhao Quanrui, Shao Shuai, and Liu Aijun

Subjects
Coupling, Reduction (complexity), Sensor array, Computer science, Scalar (mathematics), Degrees of freedom (statistics), Direction of arrival, Data model (GIS), Quaternion, Algorithm
Abstract

This paper examines the direction of arrival (DOA) estimation for polarized signals impinging on a sparse vector sensor array which is based on the maximum interelement spacing constraint (MISC). The vector array effectively utilizes the polarization domain information of incident signals, and the quaternion model is adopted for signals polarization characteristic maintenance and computational burden reduction. The features of MISC arrays are crucial to the mutual coupling effects reduction and higher degrees of freedom (DOFs). The quaternion data model based on vector MISC arrays is established, which extends the scalar MISC array into the vector MISC array. Based on the model, a quaternion multiple signal classification (MUSIC) algorithm based on vector MISC arrays is proposed for DOA estimation. The algorithm combines the advantages of the quaternion model and the vector MISC array to enhance the DOA estimation performance. Analytical simulations are performed to certify the capability of the algorithm.

Published
2021

26. Comparative Study on Chaos Identification of Ionospheric Clutter From HFSWR

Author

Lyu Zhe, Liu Aijun, Yu Changjun, Quan Taifan, and Yang Xuguang

Subjects
010504 meteorology & atmospheric sciences, General Computer Science, Computer science, chaos, ionosphere, 02 engineering and technology, 01 natural sciences, Physics::Geophysics, law.invention, Computer Science::Robotics, law, High frequency surface wave radar, 0202 electrical engineering, electronic engineering, information engineering, General Materials Science, Radar, 0105 earth and related environmental sciences, Remote sensing, General Engineering, 020206 networking & telecommunications, Surface wave, Physics::Space Physics, Clutter, nonlinear dynamical systems, lcsh:Electrical engineering. Electronics. Nuclear engineering, Ionosphere, lcsh:TK1-9971
Abstract

In addition to target echoes, high frequency surface wave radar (HFSWR) receives sea and ionospheric clutter. Among these clutters, the ionospheric clutter is dominant and significantly affects the detection performance of HFSWR, particularly when the targets are located 100 kilometers away from the radar, rendering it an unsolved problem for HFSWR. Existing studies concerning HFSWR ionospheric clutter lack empirical research on the nonlinear dynamical characteristics of the ionosphere of HFSWR as existing ionospheric suppression methods are still insufficient to adapt the project application. Therefore, the present study utilized the threshold segmentation method to eliminate the sea clutter in HFSWR Range-Doppler spectrum and extracted ionospheric signals from this spectrum by edge feature extraction. Subsequently, the chaotic invariants, such as correlation dimension and the largest Lyapunov exponent of HFSWR ionospheric clutter, were calculated by phase space reconstruction, whilst the chaotic dynamical characteristics of HFSWR ionospheric clutter were determined by the 0-1 test for chaos and other algorithms. Furthermore, the present study demonstrated, for the first time, the chaotic dynamics of the ionospheric clutter of HFSWR with a low-dimensional attractor by processing and analyzing the experimental data from the Weihai High Frequency Radar Station. The conclusion redefines HFSWR ionospheric clutter based on chaotic dynamics rather than regarding it as a stochastic process, which is conducive to efforts to explore the formation mechanism of ionospheric clutter in essence, which can ultimately improve the detection capability of HFSWR, particularly for long-distance targets.

Published
2019

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