Based on a second-stage CCFFPCs with a filling ratio of K = 3 and M = 5, keeping the central circular core radius r₁ = 0.3 a constant, different radii of circular cores are filled into the central edge positions of its basic phononic crystal. The band structures of the configurations are as follows: (a) r₂ = 0 m, (b) r₂ = 0.025 a, (c) r₂ = 0.05 a, (d)r₂ = 0.075 a, (e) r₂ = 0.0992 a.