A leaky-wave antenna array is one of the attractive candidates for high efficiency and low cost planar antennas in centimeter- and millimeter-wave applications such as auto-motive radars and radio communication devices. In this paper, a planar leaky-wave antenna array composed of a printed periodic metal strip grating on a grounded dielectric waveguide and using a coplanar feeding device for the dielectric waveguide is proposed. Antenna design examples and their simulated radiation characteristics for 10,4—10,8 GHz, 24—24,4 GHz and 36,5—37,3 GHz frequency ranges are presented.