Abstract
Today, the interrupted-sampling repeater jamming (ISRJ) has posed a serious threat to LFM radars. In this paper, a countermeasure to suppressing ISRJ based on fractional Fourier transformation (FrFT) is presented. The echo signals, mixed with ISRJ, will be processed in FrFT of specific order, and then a narrow band filter based on parameters of FrFT is designed to extract the target signals and suppress interference signal, so as to realize the target detection. The three kinds of models of ISRJ (ISDRJ, ISRRJ, ISCRJ) are introduced; the anti-jamming principles are analyzed and simulated. The simulation results show that, the algorithm has low complexity and takes short operation time, and it is effective in low SNR or high JSR condition.
Highlights
Linear frequency modulation (LFM) signal is widely used in tracking radar
The fractional Fourier transform (FrFT) in the field of radar signal processing applications has developed rapidly: Paper [4] introduces novel theorems for FRFT; the paper [5] proposed a unified focusing algorithm for several modes of SAR based on FrFT; literature [6] used FrFT for detecting targets in sea clutter; paper [7] put forward the analysis for FRFT-OFDM systems to frequency offset in time-frequency selective fading channels, [8] analysis of the intermittent sampling repeater jamming parameters influence on the performance of the interference
This paper is based on eigenvalue decomposition discrete FrFT algorithm [9,10], isolates interference and target signal
Summary
With the development of LFM interference method, jammers with digital radio frequency memory (DRFM) can accurately reproduce the received radar signals and simulate them, resulting in coherent jamming effect, especially for LFM signals. The development and perfection of interrupted-sampling repeater jamming (ISRJ) [1], which is flexible and has diverse forms, can form several false targets [2] to deceive radars, as well as creating the effect of noise suppression to a certain extent. With the flexibly change of repeating and modulation method, interference effect is improving, which has posed a serious threat to the tracking radar, so it is urgent to seek a way to counter this type of interference [3].
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