In this paper, a wide slot loop antenna with an adjustable back-reflector is introduced. Five working statuses are defined by simply adjusting the distances between the radiator and the reflector. Measured results show the total available operating band with better than 10dB return loss ranges from 0.84GHz to 3.04GHz (113.4%). The radiation properties of the array are tested in an anechoic chamber. Stable unidirectional radiations with more than 8.3dB gains are observed in the working band.