Xin Li

Nanjing Drum Tower Hospital

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Peng‐Lang Shui

Xidian University

Yanmin Zhang

Henan University

Yunhua Wang

Lanzhou University

Xiao-Yun Xia

Xidian University

Pengbo Du

Ocean University of China

Yushi Zhang

National Engineering Research Center of Electromagnetic Radiation Control Materials

Yushi Zhang

National Engineering Research Center of Electromagnetic Radiation Control Materials

Jianbo Cui

Ocean University of China

Yushi Zhang

Northeastern University

Shuwen Xu

Xidian University

Cooperative Institutions

National Engineering Research Center of Electromagnetic Radiation Control Materials

Xidian University

Chinese Academy of Sciences

Ocean University of China

Peking University

Institute of Electronics

Yanan University Affiliated Hospital

Ministry of Natural Resources

Jiangxi University of Science and Technology

Hong Kong Polytechnic University

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GRNN-Based Predictors of UHF-Band Sea Clutter Reflectivity at Low Grazing Angle

IEEE Geoscience and Remote Sensing Letters (2021)

Peng‐Lang Shui Xiao-Fan Shi Xin Li Feng Tian Xiao-Yun Xia

As a basic characteristic of sea clutter, the reflectivity of sea surface depends on many factors. Various universal empirical models of low precision have been developed to predict the reflectivity of sea surface. In this letter, a method is proposed to train specific predictors by big data learning, where the universal empirical models are embedded to the architecture of the generalized regression neural network (GRNN) to enhance the learning ability and efficiency. On the sea clutter database measured by an island-based UHF-band radar in the offshore waters of the Yellow sea of China at low grazing angle, the GRNN-based predictors of different structures are compared with other predictors. The results on the database show that the GRNN-based predictors behave better at learning efficiency, prediction precision, and robustness.

Robustness

10.1109/lgrs.2021.3076842

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Citations (12)

A new model for Doppler shift of C-band echoes backscattered from sea surface

Acta Oceanologica Sinica (2023)

Jianbo Cui Yunhua Wang Yanmin Zhang Huimin Li Shouxiang Jiang

Backscatter (email)

Empirical modelling

Sea state

10.1007/s13131-022-2144-8

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Citations (3)

Study of wind direction factor based on sea clutter in littoral environments

The Journal of Engineering (2019)

Xin Li Peng Zhao Peng‐Lang Shui Xiao-Yun Xia Shuwen Xu

Wind direction factor, as a part of some empirical sea clutter models of the normalised radar cross-section (NRCS), is closely related to wind direction angle, grazing angle and radar wavelength. The use of the low-grazing-angle (LGA) sea clutter measured by UHF-band radar on the Lingshan island to discuss the characteristic of the wind direction factor is investigated. The results indicate that the upwind-to-crosswind ratio of NRCS, which is calculated by the empirical model, could not provide a good fit for grazing angles <10°. It was found that the ratio obtained from measured data varies with the sea state (SS) at the same grazing angle, conversely the empirical models was constant. Based on deep analysis of the results, we finally find out the influence of SS could not be ignored. In addition, some suggestions to improve sea clutter model of littoral environments were proposed for practical applications.

Radar cross-section

Radar horizon

10.1049/joe.2019.0493

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中央南部チベットにおけるZhongba Gyangze推力の第三紀初期の変形【Powered by NICT】

Gondwana Research (2017)

Wang Hou-Qi Ding Lin Cai Fu-Long Xu Qiang Shun Li

Source

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Analysis of UHF-band sea clutter reflectivity at low grazing angles in offshore waters of the Yellow Sea

International Journal of Remote Sensing (2020)

Xin Li Peng‐Lang Shui Xiaoyun Xia Jinpeng Zhang Xiao-Fan Shi

Reflectivity is an important characteristic of sea clutter that depends on the parameters of the radar and the environment. This paper presents reflectivity measurements of UHF-band horizontal polarized sea clutter based upon data collected in the offshore waters of the Yellow Sea of China at low grazing angles. During the experiment, the oceanic and meteorological conditions were recorded by the Datawell Waverider 4 and Lufft WS700-UMB on the sea surface. The factors that affect the reflectivity acquisition are analysed and the selective median filtering method in average Doppler power spectrum is presented to remove the effect of ground clutter from the sidelobes of the antenna beam pattern and the normalized reflectivity of the sea surface is computed. The applicability of the four classical reflectivity empirical models to the datasets is analysed. The results show that the Hybrid (HYB) and Technology Service Corporation (TSC) models are suitable while the Georgia Institute of Technology (GIT) and Naval Research Laboratory (NRL) models are unsuitable for the UHF-band horizontal polarized sea clutter in the offshore waters of the Yellow Sea of China.

10.1080/01431161.2020.1760395

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Citations (6)

Experimental Study on the Properties of Microwave Echoes Backscattered from Breaking Waves

IEEE Transactions on Geoscience and Remote Sensing (2024)

Pengbo Du Yunhua Wang Yanmin Zhang Jianbo Cui Yushi Zhang

Microwave Imaging

10.1109/tgrs.2024.3376537

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Investigation on Electromagnetic Scattering From Time-Varying Sea With a Low-Flying Small Target Above It

Pengju Yang Xin Li Rui Wu Xuyang Ren Y. Q. Zhang

In this paper, the Doppler spectrum of backscattered echoes from moving target above time-varying sea surfaces is investigated by utilizing the quasi-stationary algorithm, i.e., approximating the time-domain problem by repeatedly implementing the frequency-domain method. In order to fast and accurately solve the composite scattering problem of time-varying sea surfaces with a Low-flying small target above it, a hybrid algorithm of Kirchhoff approximation (KA) and method method-of-moments (MoM) is utilized in this paper for analyzing the Doppler spectrum signatures. The effect of the speed of flying target on Doppler spectrum signatures of a low-flying small target above time-varying sea surface is investigated in this paper.

Electromagnetic spectrum

10.1109/compem.2019.8779188

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An Empirical Model of Shape Parameter of Sea Clutter Based on X-Band Island-Based Radar Database

IEEE Geoscience and Remote Sensing Letters (2023)

Xiao-Yun Xia Peng‐Lang Shui Yushi Zhang Xin Li Xinyu Xu

Sea clutter modelling and parameter estimation/prediction are important basis of system design, performance assessment, and target detection of maritime radars. Besides parameter estimation from measured data, parameter prediction from radar parameters, sea state, and the viewing geometry of the radar is an alternative way. In this letter, a dual-polarimetric full-recorded sea clutter database measured by an island-based X-band experimental radar on the Yellow sea of China is introduced. On this database, the model selection reveals that the compound-Gaussian model with inverse Gaussian (CGIG) texture is suited for HH high-resolution sea clutter data, the generalized Pareto (GP) intensity distributions are for HH moderate-resolution data, and the K amplitude distributions are for high and moderate-resolution VV polarized data. Further, three five-parametric empirical formulae are constructed to predict the shape parameter of the CGIG, GP, and K distributions of sea clutter from the area of spatial resolution cell, the grazing angle, the significant wave height, the average wave period, and the wave direction relative to the sight line of radar. The new empirical formulae attain more accurate prediction than existing empirical formula on the database.

Significant wave height

10.1109/lgrs.2023.3266260

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Citations (7)

Study on Radar Scattering Characteristics of Breaking Wave

2022 Photonics & Electromagnetics Research Symposium (PIERS) (2024)

Pengbo Du Yunhua Wang Yanmin Zhang Jianbo Cui Yushi Zhang

10.1109/piers62282.2024.10618412

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External Calibration of P-Band Island-Based Sea Clutter Measurement Radar on the Sea Surface

IEEE Transactions on Geoscience and Remote Sensing (2020)

Xin Li Peng‐Lang Shui Zhedong Zhang Yushi Zhang Shuwen Xu

Radar external calibration is an important measurement in determining the radar cross sections of unknown targets and the reflectance coefficients of the sea surface. This measurement is often made in an anechoic chamber by standard programs. Sometimes, this measurement must be made in outdoor conditions, and the ambient environment severely affects the calibration precision. Thus, the scheme of the measurement must be specially designed. In this article, a calibration conducted at the sea near Lingshan Island is reported, and a full program of an external calibration on the sea surface and relevant analysis are presented for a P-band island-based sea clutter measurement radar. Data analysis shows that the multipath effect from the sea surface is a major factor to degrade the precision of the calibration. Measurement data over 4 days and the multipath reflectance model of the sea surface are combined to estimate the power increment from the multipath effect. Radar system constant is estimated based on the estimated power increments at different sites, where the viewing geometries of the radar are different. The results show that the proposed external calibration method on the sea surface attains a satisfactory precision.

Radar horizon

Anechoic chamber

X band

10.1109/tgrs.2020.3023714

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Citations (5)