The authors propose a discrete wavelet transform-based unsupervised underdetermined blind source separation methodology for radar pulse deinterleaving using a novel parameter, i.e. the radar antenna scan pattern. Deinterleaving becomes a challenging task in case of dense pulse scenario with parameter agile radars and the authors show that the scan pattern is an excellent parameter for this task. The results also indicate that the methodology is very suitable in case of jittered and staggered pulse repetition interval with reduced missing pulses and false alarm rate. Based on deinterleaved scan pattern information, a preliminary assessment of the number of emitters and their threat levels can be done. © The Institution of Engineering and Technology 2019