Beam steering antenna is expected in 60GHz wireless communication system to improve the signal to noise ratio and obtain high gain with wide cover range for high speed WPAN application. In this paper, patch antenna arrays with planar topology are investigated by synthesizing the network losses and devices such as phase shifters. The investigation results can provide a valuable guide line for the further implementations to the highly integrated beamforming systems. Moreover, the array antenna system perfor-mances, i.e. maximum gain, directivity, radiation patterns, element phase sensitivity, are analyzed under different element number and based on electromagnetic simulation and computational methods. It is found that the half wavelength square patch arrays can obtain maximum ± 45° angle scanning range in E-plane and ± 40° range in Hplane with peak gain variation of 3dB. It can be shown that to achieve 6dBi gain with ± 45° beam steering range, a 13-element array with inter-element spacing of λ 0 and full 360° phase shifter are required if only passive components are employed.