A Method for improving signal-to-noise ratio and accuracy in detecting micromotion features carried by photon-level targets echo based on micromotion modal decomposition

This paper proposes a novel Micromotion Modal Decomposition (MMD) method to solve the problems of reduced signal-to-noise ratio (SNR) and limited detection capabilities of target micromotion features caused by target micromotion in photon-level weak echo detection. A complete model of photon-level weak echo photon heterodyne detection based on the MMD method is constructed and proof-of-concept experiments are conducted. The experimental results show that the MMD method can effectively concentrate the energy of the target echo to the micromotion parameters corresponding to its micromotion mode. Compared with the traditional spectral decomposition (TSD) method which scatters the energy of the target echo in the spectrum, the MMD method can increase the SNR by 5 times. For target echoes with an average power of $9\times 10^{-15}W$, MMD can achieve millimeter-level micromotion amplitude detection accuracy for targets with a micromotion frequency up to 111 Hz. The MMD method improves the detection capabilities of target micromotion features under weak echo conditions. In addition, this method can discriminate and detect multiple targets within the same field of view. This advance is of great significance for the detection of micromotion features of small targets at long distances.