Abstract: To meet the requirements of electrical downtilt beam patterns and broad bandwidth for the indoor wall mounted base station antennas, a symmetrically right angled slot is loaded into the low profile square patch antenna. The ex perimental results show that the relative impedance bandwidth with the parameter S11 less than -10dB is 5. 15% for the de signed antenna. Over the operating frequency band, the electrical downtilt of radiation beams is about 30毅. Meanwhile the downtilt can be adjusted by changing the feed position. In the angle range 120毅of the horizontal plane pattern, the radiation level of the vertically polarized electric field is 10dB higher than the horizontal polarization, which indicates that the antenna has the radiation characteristics of vertically linear polarization. Over the working band the antenna gain is about 6dBi. The presented antenna can be built into the wall mounted base station to reduce the device size.