Photonic fractional Fourier transformer for chirp radar with ghost target elimination.

For the first time, to the best of our knowledge, we propose a photonic fractional Fourier transformer (PFrFTer), which is used in chirp radar for detecting multiple non-cooperative targets. Based on photonic rotation of the time-frequency plane, the optimal fractional Fourier domain is formed, and the received broadband chirp signals are projected on it, where they behave as impulses. Moreover, through manipulating the fractional Fourier transform spectrum, the PFrFTer contributes to the cancellation of two ghost target sources, so that the ghost targets in multiple-target circumstances are removed. The simulation and experimental results show that the proposed PFrFTer can adapt to multiple non-cooperative targets environments and is immune to ghost targets at optimal working conditions, which agrees well with the theoretical analysis.