In this paper, a modified microstrip branch-line coupler (BLC) at 1.6 GHz is designed and simulated. The proposed BLC consists of open stubs and resonators together. The designed BLC correctly works at the operating frequency and suppresses 2nd up to 13th unwanted harmonics. The applied resonator in the BLC structure has a small size of 0.15λg×0.081λg with a 1.8 GHz main frequency. This applied resonator has a sharp response in the transition band and provides a sharp roll of the rate of 185 dB/GHz. The proposed BLC has good performance at 1.6 GHz, the insertion loss parameter is 0.3 dB, whereas |S14| and |S11| are more than 20 dB. Moreover, the proposed BLC provides an ultra- wide rejection band of 2 - 20 GHz.