Techniques for Mitigating the Impact of Intra-CPI Waveform Agility

As the electromagnetic spectrum has become more congested, there has been increased interest in spectrum sensing and sharing techniques that enable frequency agility on a pulse-to-pulse basis within a single coherent processing interval (CPI). Although intra-CPI pulse agility allows for more efficient spectrum use, it creates unique processing challenges. Changing the bandwidth and intermediate frequency (IF) of pulses within a CPI reduces the performance of traditional range-Doppler processing techniques. This paper investigates the impact that bandwidth and IF frequency agility has on the slow time phase history and range sidelobes. To mitigate the effects of frequency hopping, a modified backprojection technique is proposed. Second, mismatched filtering techniques are examined to mitigate the range-sidelobe modulation (RSM) caused by the changing bandwidths. This work will investigate these two issues individually and repair each in turn before combining the process to compensate fully adaptive CPIs. Simulated data will be used to validate the performance of each technique using linear frequency modulated (LFM) waveforms. The mitigation techniques are further verified using real-world data from an agile pulse-Doppler radar experiment.