Abstract: In order to realize two fixed beam directions in an antenna array with a relatively wide operating bandwidth, this paper proposes a method for designing a feeding network in which the phase difference is frequency-dependent. The ratio of the phase difference to the operating frequency of the proposed feeding network is designed to be constant across the frequency range, which means that a phase difference of φ at f₀ and 2φ at 2f₀ is realized. The transmission line structure of the feeding network is a stripline. The radiation unit in the antenna array is Vivaldi antenna. The feeding network was designed and fabricated, and the measured results were in general agreement with the simulated results. The antenna array fed by this feeding network achieves two fixed-direction beams in the frequency range of 2-4 GHz, which is in good agreement with the theoretical analysis. The designed broadband antenna array system has the function of maintaining a stable beam direction over a wide bandwidth range, providing a potential solution for dual-area coverage.