A periodic metal array structure can be disposed between two antenna modules and include rows of metal unit assemblies that each includes metal units connected to each other in a longitudinal direction. Each metal unit has a first longitudinal strip, two first transverse strips, two second transverse strips, and two second longitudinal strips having shorter longitudinal lengths than that of the first longitudinal strip, and being respectively disposed on the left and right sides of the first longitudinal strip and respectively spaced apart therefrom by intervals at which the second transverse strips are located. The top and bottom ends of the first longitudinal strip are respectively connected with the first transverse strips. At least one first transverse strip can be connected to a first transverse strip of an adjacent metal unit. Each second transverse strip can be connected to the first longitudinal strip and a corresponding second longitudinal strip.