Spatial Spectrum Direction Finding by Programmable Metasurface With Time Modulation

A novel direction-finding method based on programmable metasurface and time modulation theory is proposed and verified. Its principle is as follows. First, period phase modulation is added to all elements in the metasurface, and the corresponding harmonic components are generated and combined together. Second, the array's manifold vector can be recovered from the Fourier coefficients of harmonic components in the received signal. Finally, the high accuracy direction finding can be realized by classical spatial spectrum estimation methods, and the direction finding of coherent signals is discussed. Numeric simulations are provided to verify the feasibility of the proposed method. A C-band direct radiant programmable metasurface with
$\text{16} \times \text{16}$
elements is fabricated, which reduces the profile of the antenna equipment used for direction finding and improves the accuracy due to the efficient energy utilization caused by phase modulation. The experimental results agree with both the numerical simulation and the theoretical analysis very well, which verifies the effectiveness of the proposed method.