Dielectric Resonator Antennas are becoming very attractive in many applications in today''s technology. This work emphasizes on the half cylindrical dielectric resonator antennas applied in the 5.2/5.8GHz WLAN. It also explains the principles of dielectric resonator antennas and offers a simplified theoretical understanding of the modes excited inside resonators with different shapes. Design principles are also explained. Some measured results are also included to give a better understanding to the practical limitations when designing such an antenna.