Aerospace and Electronic Systems Magazine March 2018 - 32

Feature Article:

DOI. No. 10.1109/MAES.2018.170036

Experimental Analysis of a HF Hybrid Sky-Surface
Wave Radar
Yinsheng Wei, Peng Tong, Rongqing Xu, Lei Yu, Harbin Institute of Technology, Harbin,
China

INTRODUCTION
High-frequency (HF) radar systems exploit refractive and diffractive properties of HF waves to sense targets beyond the line of
sight. HF skywave radars use the ionosphere medium to reflect
the signals and thus illuminate targets of thousands of kilometers
away, but they suffer from the close-distance blind zone and severe
ionosphere decorrelation effect. HF surface wave radars exploit the
diffraction of vertically polarized waves to detect targets within
hundreds of kilometers offshore. But the diffracted surface wave
is highly attenuated, and the radar has the vertical incidence ionospheric clutter problems. High-frequency hybrid sky-surface wave
radar (HFSSWR) is a novel radar configuration containing a skywave transmitting path and a surface wave receiving path, which is
a natural combination of HF skywave and HF surface wave radar
systems [1]. In addition, multiple separate receiving sites can compose a multistatic network and operate with only one transmitter.
The system configuration is flexible.
Several experimental systems have been constructed by using
the existing HF skywave transmitting sites and HF surface wave
receiving sites [2], [3]. In 2007, an experimental system with a
single skywave transmitter and multireceiver was investigated in
Australia to detect target via the line-of-sight receiving path. Typical small to medium aircraft targets have been detected as far as
the line-of-sight horizon [2]. In 2008, U.S. researchers constructed
a similar system, which was called skywave line-of-sight HF radar.
Adaptive beamforming algorithms were evaluated for application
to mitigate the direct signal interference [3]. There is also interest
in passive hybrid radar using emitters of opportunity [4], [5]. The
receiving paths of all previously mentioned radars are line of sight.
The resolution capability and detection performance against
ship targets for the HFSSWR have been studied in various papers
[6], [7]. It was found that spread first-order Bragg echoes may
mask echoes of ships sailing at a specific speed range and form
Authors' current address: Y. Wei, P. Tong, R. Xu, L. Yu, Harbin
Institute of Technology, P.O. Box 338, Department of Electronic
Engineering, No. 92 Xidazhi Street, Nangang District, Xinjishu
Building, Room 803, Harbin, Heilongjiang 150001 China, Email: (tongpeng@hit.edu.cn).
Manuscript received January 31, 2017, revised July 15, 2017,
and ready for publication October 11, 2017.
Review handled by D. O'Hagan.
0885/8985/18/$26.00 © 2018 IEEE
32

a blind zone. Researchers from Harbin Institute of Technology
(HIT), China, analyzed the first-order sea clutter characteristics
theoretically and experimentally [8].
The ionosphere as a reflective medium is a double-edged
sword. The nonstationarity of ionosphere spreads the clutter spectrum in the spatial and Doppler dimension, which severely affects
the detection performance. A team from Canada contributes to
ionospheric clutter model research. They derived the first- and second-order HF radar clutter power and its clutter radar cross-section
(RCS) for ionosphere-ocean mixed-path propagation [9]-[11]. Researchers from HIT studied the broadening first-order sea clutter
spectrum based on a modified first-order sea clutter RCS model
and proposed the ionospheric decontamination and sea clutter suppression methods [12]-[15].

SYSTEM DESCRIPTION
OPERATIONAL CONCEPT
The principle for the operation of the HFSSWR is illustrated in
Figure 1. The skywave transmitting station is located over the horizon and illuminates the search region via wave reflection from
the ionosphere. The echoes scattered from any targets in the illuminated area propagate to the receiver by surface wave path or line
of sight. The receiving system can be located on shore or on ship.

Figure 1.

The layout diagram of HFSSWR.

IEEE A&E SYSTEMS MAGAZINE

MARCH 2018

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