Shipborne HFSWR Virtual Aperture Extension Method Based on RD-Domain Time–Frequency Information Fusion

Due to the limited platform space of shipborne high-frequency surface wave radar (HFSWR), the aperture of the antenna array is reduced, thereby degrading the radar’s direction of arrival (DOA) estimation performance. Traditional aperture extension methods, based on single-domain information, limit the aperture extension ability and are not applicable to scenarios where nontarget signals dominate. To address the above issues, this letter proposes an aperture extension method based on range-Doppler domain time–frequency information fusion (RDTFF), which utilizes multiple carrier frequencies and time division techniques. Compared with traditional methods, the proposed method achieves target echo separation and extraction through RD-domain processing, thereby extending the aperture and making the method suitable for shipborne HFSWR scenarios. In addition, by fusing the time–frequency information of the target echo, a larger virtual aperture can be obtained, which further improves the DOA estimation performance of the array.