Using Sky‐Wave Echoes Information to Extend HFSWR's Maximum Detection Range

Abstract

High Frequency Surface Wave Radar's (HFSWR) main propagation mode, ground wave, can only spread to about 500 km as ground attenuation, much shorter than sky wave that can spread to thousands of kilometers through ionospheric reflection. Due to the poor steerability of HFSWR's vertical directional diagrams, sky‐wave echoes (ionospheric echoes) can also be received in HFSWR, which could be used to extend HFSWR's maximum detection range. Nevertheless, the delay time of long‐range target echo may exceed the pulse repetition period when the target exceeds the original maximum detection range, resulting that the target cannot be detected correctly, which is the so‐called range ambiguity. To maintain HFSWR's performance within its original maximum detection range, we consider using P4 polyphase code's cross‐correlation properties to solve the range ambiguity rather than changing the parameters of the transmitted signal or using multipulse repetition frequency signal. In this paper, we analyze HFSWR's multipath phenomenon first. Then we propose a range ambiguity resolution method to detect long‐range target correctly with P4 code cross‐correlation properties. Subsequently, we give the simulation data processing result, which testifies that using P4 code cross correlation can solve range ambiguity correctly and can extend the maximum detection range to P (group number of P4 code) times the original maximum detection range. Finally, we process the actual data collected in Weihai, China, with this method and detect some targets beyond the original maximum distance.

Experimental Observation and Analysis of Ionosphere Echoes in the Mid-Latitude Region of China Using High-Frequency Surface Wave Radar and Ionosonde

“…The Doppler spectrum corresponding to a relatively low pulse repetition frequency (PRF) is much cleaner with distinct Bragg lines and lower noise than that obtained at a high PRF. Additionally, by employing a split complementary P4 code as a transmitting waveform to overcome range ambiguity, HFSWR can even detect targets at a distance of 1000 km via the skywave propagation path, similar to over-the-horizon radar (OTHR) [27]. In summary, there are two types of ionospheric echo propagation paths: one is the skywave path passing through the ionosphere, and the other is the mixed path involving both the ionosphere and the ocean surface.…”

“…1) To confirm the existence of HFSWR ionospheric echoes due to skywave propagation paths [24] in addition to the vertical reflection path and ionosphere-ocean mixed path [23], [25], [26]. Some researchers proposed four possible propagation paths involving the combination of all ground-wave paths and skywave paths [27]- [29].…”

An Improved Grid-Search Method for the Identity-Test of Ionosphere-Layer Virtual Heights via TDOA Measurements

“…Consider the single-layer spherical reflection model as shown in Fig. 1, which is a widely used transmitting model in sky-wave localization [22], [23]. Then the time delay of the transmitting path from signal source (B) to sensor (A) is AC +B C, where C is the equivalent reflection point.…”

Multi‐mode target tracking in combined sky‐wave and surface‐wave monostatic high frequency radar

“…In addition, CSSM‐HF radar uses a pulse signal to detect a target, and Zhao et al . [2, 3] have studied the signal suitable for this radar system. As this radar system uses multiple propagation modes to detect targets and the detection range of different modes partially overlaps, so some targets may have several echoes, resulting in false tracks.…”