In this paper, the linearly-and circularly-polarized (LP or CP) beamwidths of low-profile microstrip patch antennas (MPAs) are summarized based on our previous works. Herein, the equivalent magnetic currents (EMCs) are used to analyze the radiation beams. Firstly, the half-power beamwidth (HPBW) of the LP MPA is studied, its HPBW could be significantly widened by using a single EMC. Secondly, the axial-ratio beamwidth (ARBW) of the CP MPA is extensively analyzed. It shows that its ARBW could be obviously extended by controlling the spacing between these EMCs. With these arrangements, both of these antennas are fabricated and measured finally. The measured results show that the HPBW of LP antenna could be obviously extended from 80° to around 135°. Meanwhile, the 3-dB ARBW of the CP antenna could be increased from 50° to 140° as desired.