An Improved Multi-period LFM Interference Suppression Method Based on Short-Time Fractional Fourier Transform

The fractional Fourier transform (FRFT) provides a valuable tool for the linear frequency modulation (LFM) signal. However, it is not suitable for suppressing multi-period LFM interference. To achieve better anti-jamming performance, we have to overcome numerous obstacles, chief among which are the need for windowing the signal to a single cycle and alleviating the calculation burden. To mitigate the interference, we propose in the current paper an improved method based on the short-time fractional Fourier transform, which can directly estimate the interference signal period and improve interference filtering performance. We take the B1C frequency signal of the BeiDou GNSS receiver as an example to carry out a numerical simulation to compare the improved short-time fractional Fourier transform (STFRFT) method with the traditional one. The results yield in the experiment showed that much better results are observed, in terms of computation burden and acquisition results, especially for a high interference-to-signal ratio (ISR) environment.