Abstract:As modulated by the ionosphere, the classical High-Frequency (HF) model of ocean clutter can not describe the HF scatterings from sea surface approvingly in view of skywave Over-The-Horizon Radar (OTHR). In this paper, ocean current is taken into consideration based on the Walsh HF sea clutter model. An equivalent ionospheric reflecting screen model is established which can be resolved into several sub screens, based on which the ionospheric modulation on frequency is discussed. Incorporating with Walsh model, a normalized sea clutter model for skywave OTHR is presented. Using the presented model, the spectrums in different cases involving Doppler shift, spectrum broadening, splitting and multipath propagation are simulated, and comparing with the measured data, the model’s validity and robustness are verified.
CROMBIE D. Doppler spectrum of sea echo at 13.5 MHz[J]. Nature, 1955, 175(4): 681-682. doi: 10.1038/175681a0.
[2]
BARRICK D. First-order theory and analysis of MF/HF/ VHF scatter from the sea[J]. IEEE Transactions on Antennas and Propagation, 1972, 20(1): 2-10. doi: 10.1109/TAP.1972. 1140123.
[3]
BARRICK D. Remote sensing of sea state by radar[C]. IEEE International Conference on Engineering in the Ocean Environment, Rhode Island, USA, 1972: 186-192. doi: 10.1109/OCEANS.1972.1161190.
[4]
HISAKI Y and TOKUDA M. “VHF and HF sea echo Doppler spectrum for a finite illuminated area”[J]. Radio Science, 2001, 36(3): 425-440. doi: 10.1029/2000RS002343.
[5]
GILL E, HUANG W, and WALSH J. On the development of a second-order bistatic radar cross section of the ocean surface: A high-frequency result for a finite scattering patch [J]. IEEE Journal of Oceanic Engineering, 2006, 31(4): 740-750. doi: 10.1109/JOE.2006.886228.
[6]
WALSH J, ZHANG J, and GILL E. High-frequency radar cross section of the ocean surface for an FMCW waveform[J]. IEEE Journal of Oceanic Engineering, 2011, 36(4): 615-626. doi: 10.1109/JOE.2011.2161706.
LIU Y X. Experimental research on the inversion of wind fields over the sea with HF radar[D]. [Master dissertation], Harbin Institute of Technology, 2015: 7-20.
CAI W H. A study and simulation of the sea clutter high-frequency radar cross sections for a moving platform[D]. [Master dissertation], Harbin Institute of Technology, 2015: 6-42.
DING F, LI J N, YANG L Q, et al. The experimental research on remote the wind direct and radial current in HF hybrid sky-surface wave radar[J]. Chinese Journal of Radio Science, 2016, 31(4): 755-759. doi: 10.13443/j.cjors.2015091001.
[10]
HOU C Y, KE G, and FU Y L. The sky-wave radar detection performance computing based on the dynamic ionospheric model[J]. Neurocomputing, 2015, 151, 1305-1315. doi: 10.1016 /j.neucom.2014.10.073.
[11]
BILITZA D. International reference ionosphere 2000: Examples of improvements and new features[J]. Advances in Space Research, 2003, 31(3): 757-767. doi: 10.1016/S0273- 1177(03)00020-6.
WEI N, LIU W, LU Z X, et al. The electron density profile inversion for incompletely developed case of F1 layer[J]. Chinese Journal of Geophysics, 2016: 59(3): 778-790. doi: 10.6038/cjg20160302.
NIU R C, GUO C J, and ZHANG Y R. Study of ionospheric delay model considering second-order effects[J]. Computer Engineering, 2016: 42(1): 300-303. doi: 10.3969/j.issn.1000- 3428.2016.01.053.
[14]
BAKER D and LAMBERT S. Range estimation for SSL HFDF system by means of a multi-quasi parabolic ionosphere model[J]. IEE Proceedings H-Microwaves, Antennas and Propagation, 1989, 136(2): 120-125. doi: 10.1049/ip-h-2.1989. 0022.
FENG J, NI B B, ZHAO Z Y, et al. Reconstruction of horizontally-inhomogeneous ionospheric structure using HF skywave backscattering ionograms[J]. Chinese Journal of Geophysics, 2016, 59(9): 3135-3147. doi: 10.6038/ cjg20160901.
ZHANG J Z. Research on target location correction methods under the mixes propagation mode[D]. [Master dissertation], Harbin Institute of Technology, 2016: 8-18.
[17]
DYSON P and BENNETT J. A model of the vertical distribution of the electron concentration in the ionosphere and its application to oblique propagation studies[J]. Journal of Atmospheric & Terrestrial Physics, 1988, 50: 251-262. doi: 10.1016/0021-9169(88)90074-8.
[18]
MARESCA J and BARNUM J. Theoretical limitation of the sea on the detection of low Doppler targets by over-the- horizon radar[J]. IEEE Transactions on Antenna and Propagation, 1982, 30(5): 837-845. doi: 10.1109/TAP.1982. 1142910.
LUO H and CHEN J W. Performance evaluation of ionospheric phase contamination correction approaches for over-the-horizon radar[J]. Journal of Astronautics, 2013, 34(2): 262-269. doi: 10.3873/j.issn.1000-1328.2013.02.016.
YOU W, HE Z S, CHEN X Y, et al. Skywave radar decontamination based on the cubic phase model[J]. Chinese Journal of Radio Science, 2012, 27(5): 875-880. doi: 10.13443 /j.cjors.2015.05.016.
MA H W. Research and simulation analysis for sea cluster character of high frequency radar[D]. [Master dissertation], Harbin Institute of Technology, 2011: 10-12.