Study on interference suppression based on joint fractional Fourier domain and time domain

An interference suppression algorithm is proposed to meet challenges of the traditional technique in dealing with the linear frequency modulation (LFM) interference, such as high loss of signal-to-noise ratio (SNR), the output signal-to-interference- plus-noise ratio (SINR) sensitive to input interference-to-signal ratio (ISR) that results in an unstable synchronization, and the spectrum leakage serious in strong ISR situation. This approach firstly makes use of the windowed and lapped technique to the fractional Fourier transform (FRFT) to enhance the ISR improvement and lower the SNR loss. Then by weakening the interference and a secondary threshold process, interference energy can be suppressed as much as possible and the output SINR is less sensitive to the ISR. Finally, a joint fractional Fourier domain and time domain technique is proposed to overcome the residual interference energy caused by the strong interference or the discontinuous-phase interference. Theoretical analysis and simulation results show that the proposed algorithm can achieve better performance than the conventional methods in suppressing both the multi period LFM interference and the multi chirp-rate LFM interference, especially in the strong interference environment.