In this paper, design of broadband microstrip line fed cavity backed slot antenna with very small cavity height of 0.08 lambda is proposed. The antenna is designed for 1.8 GHz frequency band with wider beam coverage in E-plane. Parametric analysis of antenna is carried out to optimize antenna design for smaller cavity height, broad bandwidth and wider beam coverage. The radiation characteristic of antenna for different sizes of ground plane is analyzed in detail. Measured results of antenna with different ground plane sizes are presented. The Antenna has VSWR <;2 bandwidth of 18% and maximum gain of 7.2 dBi with wide beam coverage in E-plane.