A conical-beam circularly-polarized microstrip antenna array composed of four square-shaped radiating elements has been proposed. In the presented antenna array all of radiating elements are fed with equal-amplitude and in-phase signals and the excitation signal is guided to the center of the array through the via, to achieve both appropriate polarization properties and the conical radiation pattern. The paper includes the design details as well as simulation and measurement results of the manufactured antenna array designated for ceiling mount Doppler sensors operating at 10.5 GHz.