Ocean surface current measurement with high-frequency hybrid sky–surface wave radar

Azimuth Resolution Improvement and Target Parameters Inversion for Distributed Shipborne High Frequency Hybrid Sky-Surface Wave Radar

“…The shipborne HFHSSWR not only maintains the capacity of long range over the horizon target detection and wide-area coverage of the HF sky-wave radar, but also retains the stability and long integration time of the HF surface wave radar (HFSWR). It also has the advantage of maneuverability of the shipborne HFSWR, which has an advancement in wide-area surveillance of over-the-horizon targets and ocean environment [4][5][6][7][8][9][10][11][12][13][14][15][16][17]. However, the shipborne HFHSSWR suffers from low azimuth resolution and poor estimation accuracy in azimuth, due to the small array aperture limited by the confined space on a shipborne platform.…”

Correction of Ionospheric Distortion on HF Hybrid Sky‐Surface Wave Radar Calibrated by Direct Wave

“…HFHSSW radar has an advancement in large-scale environment surveillance and early warning. In the recent decade, a few studies about HFHSSW radar have been conducted on system simulation (e.g., Chen, Huang, & Gill, 2016;Chen et al, 2016aChen et al, , 2016bJiang et al, 2011;Jiao et al, 2007;Li et al, 2016;Walsh et al, 2014Walsh et al, , 2015, system designation and experiment (e.g., Cui et al, 2016;Zhao et al, 2013), application in target over-the-horizon detection (see, e.g., Riddolls, 2007Riddolls, , 2008Zhang et al, 2014), and ocean surface dynamic parameters inversion (see, e.g., Ji et al, 2017;Li et al, 2017Li et al, , 2018.…”

“…In literatures, a few researches had been done for the correction of radar returns perturbed by ionosphere in HFHSSW radar system (see, e.g., Li et al, ; Ji et al, ; Zhu et al, ); these works represent largely the art of the moment in dealing with the decontamination of ionospheric distortion on high‐frequency over‐the‐horizon radars (see, e.g., Bourdillon et al, ; Parent & Bourdillon, ; Howland & Cooper, ; Anderson & Abramovich, , ; Xing & Bao, ; Lu et al, , Lu et al, ; Liu et al, ) and ionospheric clutter modeling for cases of vertical incidence and ionosphere‐ocean mixed path propagation (see, e.g., Walsh et al, , Walsh et al, ; Chen et al, , Chen, Huang, & Gill, ). The decontamination algorithms can be classified into three categories according to the data processing method.…”

“…For high‐frequency over‐the‐horizon radar, the two first‐order Bragg peaks of sea echoes, which distribute nearly symmetrically at 0‐Hz point of the radar's Doppler spectra, have been used as the calibration signal (see, e.g., Bourdillon et al, ; Howland & Cooper, ; Li et al, ). While for HFHSSW radar, the echoes of direct wave from the ionosphere is also a choice besides the Bragg peaks (Ji et al, ). The echoes of direct wave experienced only the phase distortions caused by the ionosphere without experiencing sea attenuation; therefore, the distortion of phase extracted from the frequency point of direct wave is more suitable to compensate for the ionosphere‐distorted radar echoes from sea surface.…”

“…It is reported that the radio wave transmitted by HFHSSW radar is reflected mainly by the F layers of the ionosphere, partly from E layer (Ji et al, ). The electron densities of ionospheric F 2 layers share the same variation in a region usually ranging in thousands of kilometers in horizontal and decades of kilometers in vertical (see, e.g., Rishbeth, ; Kouris & Fotiadis, ).…”