The detection performance of high-frequency surface wave radar (HFSWR) is highly susceptible to radio frequency interference (RFI). The fact that external RFIs will turn into a chirp signal and the fractional Fourier transform (FRFT) is a potent tool to analyze the chirp signal, motivates us to use FRFT in interference mitigation. In this letter, two new RFI suppression schemes are proposed, of which one is based on hybrid used of FRFT and autoregressive (AR) linear prediction algorithm, another is based on joint FRFT and recursive least squares (RLS) adaptive filtering algorithm. The simulation result indicates that the proposed schemes can effectively mitigate external RFIs even when the interferences cover Bragg peaks. The experimental result shows that the proposed schemes can effectively suppress RFI without losing echoes, and the signal to noise-plus-interference ratio is improved by 6 dB on average after RFI suppression.

中文翻译：

---

使用基于分数傅立叶变换的滤波算法减轻 HFSWR 中的射频干扰

高频表面波雷达（HFSWR）的探测性能极易受到射频干扰（RFI）的影响。外部 RFI 将变成线性调频信号，而分数傅立叶变换 (FRFT) 是分析线性调频信号的有效工具，这一事实促使我们使用 FRFT 来减轻干扰。在这封信中，提出了两种新的 RFI 抑制方案，其中一种基于 FRFT 和自回归 (AR) 线性预测算法的混合使用，另一种基于联合 FRFT 和递归最小二乘 (RLS) 自适应滤波算法。仿真结果表明，即使干扰覆盖了布拉格峰，所提出的方案也能有效地减轻外部 RFI。实验结果表明，所提出的方案能够有效抑制 RFI 且不丢失回波，