In this paper, a thin film bulk acoustic wave resonator (FBAR) with a topology of parallel inductors and an external matching circuit was used to realize broadband filtering. A 3D structure simulation of FBAR was performed using Comsol software to extract the curve corresponding to the optimal electrode shape (variable trace pentagon) into the ADS in conjunction with the external matching circuit for band expansion. It was found that the values of inductor Ls in the external matching circuit directly affect the filter bandwidth. After adjustment, the relative bandwidth of 21.15% was achieved at the series resonant frequency of fs=1.97 GHz and parallel resonant frequency of fp=2.03 GHz, which corresponds to a 3 dB bandwidth of 419 MHz and an out-of-band rejection of 11.616 dB at 1 GHz.