A new planar array antenna with special beam shaping for ETCS-RSE (Electronic Toll Collection System-Road Side Equipment) is presented. The proposed 10x10 array antenna was obtained flat-topped radiation pattern by using Woodward and Lawson pattern synthesis. The measured electrical performances of the fabricated antenna in an operating band of 5.79 ~ 5.85 GHz showed VSWR of less than 1.72, antenna gain of more than 14.3dBi, and 3dB beam width of about 33 o , low side lobe level of more than 26dB outside of ±34 o .