Using alpha-phase modulation method to solve range ambiguity for high frequency surface wave radar

A new type of high frequency surface wave radar (HFSWR) system consisting of a close-range detection using surface wave path and a long-range detection using skywave path are proposed in this paper. An important portion of this system is to design a signal that can detect longer distance targets, which is the main content of this paper. To minimize the changes to the existing radar system, this paper phase-modulates the original transmitted signal to mitigate range ambiguity. This method is applicable to all kind of single pulse repetition frequency (PRF) original transmitted signal and can manage the received signal in the region of eclipse (where the received signal is incomplete). The simulation results of different original transmitted signals (constant-frequency pulse and P4 phase-coded signals) verify that the long-range target can be correctly detected through this method. Finally, the real data collected at Weihai, China is processed. Comparing the flight information of Automatic dependent surveillance-broadcast (ADS-B) at the time when the data was recorded, two tracks that match the actual flight information in course and positions were found near 900 km (Shuozhou), flying to Hohhot.