Real time extraction of tracking error signal in IR seeker with a plus stationary reticle

Abstract

In non-imaging IR seekers, the reticle will modulate the received radiation from the target. The modulation signal contains the tracking error signal (TES), which is the main signal in IR seeker. In IR seeker with a plus stationary reticle, the accuracy of TES extraction may be affected by several items, such as noise from engines, shine background, jamming and changes in the radius of target image spot (TIS). These reasons will decrease the accuracy of target positioning and may push the target to the nonlinear region. In the nonlinear region, the target will be lost although it remains in the field of view (FOV). In this paper, we introduce a new algorithm to extend the linear region, and then, we use the cross-correlation function to decrease the undesirable effects of noise and changes in the radius of TIS. All algorithms have been simulated in Matlab and implemented in Raspberry Pi 3 Model B+. The simulation results showed that the new algorithm with cross-correlation extend the region more than 100 times on the reticle plane, where the error in phase less than 2° compared with other algorithms in this field, especially in the presence of noise. The implementation using Raspberry Pi was in real time because the total execution time for one period was less than 3 ms, which is less than strict timing window in our problem.