A wideband filtering antenna loading with U-shaped parasitic patches (UPP) is proposed by the characteristic mode analysis (CMA). The antenna is consisted of two dielectric substrates, one of which is printed with an eight-sawteeth patch, four single-sawteeth patches and two pairs of U-shaped parasitic patches. The sawteeth structures enable the two distinct characteristic modes to be closer with a smaller frequency space while allowing them to coexist within the operating frequency band, significantly enhancing the bandwidth. The two pairs of UPP can generate low-frequency and high-frequency radiation nulls, respectively. Utilizing CMA, potential modal nulls are identified at 4 GHz in the low stopband and at 7.5 GHz in the high stopband. Upon excitation with an L-shaped probe, the antenna exhibits radiation nulls precisely at 4 GHz and 7.41 GHz. The antenna's dimensions are 0.94λ