In the fifth-generation (5G) wireless communications, due to the advantages such as wide range and low cost, sub-6 frequency band is widely used. It is a challenge to develop the antennas for sub-6 base stations which are wide band, high gain and compact. In this paper, a center-fed collinear antenna array with a compact size is developed based on the turnstile antenna. Non-uniform dipole array has been used to achieve broadband so that the disadvantages of series can be improved. The gain bandwidth has been significantly increased as compared to uniform array antennas. Wider directivity gain bandwidth of 35% is provided by the non-uniform array. The proposed array antenna can be used to omnidirectional radiation applications. The directivity gain bandwidth reached to 20.7% better than traditional series-fed antennas.