Synthetic Aperture Radar (SAR) is one of the most common methods for high resolution imaging of the ground. Like all kinds of radars, the SAR antenna is used to transmit and receive signals; although, the desired specifications of SAR antennas shouldbe deduced from system required parameters. In this thesis, the design and simulation of an antenna for theSAR application ,with specified imaging characteristics, is proposed. The antenna must represent an impedance bandwidth of more than 10% in Ku-band. First, the antenna desired characteristics are derived from system parameters. In order to comply with the requirements like ligth weight and also high gain, the microstrip array antenna is proposed. Proximity coupled feed and U-shaped slot patch are simultaneously used to overcome the microstrips inherent narrow bandwidth. In addition, the desired bandwidth is obtained byusing a two-layer structure which can be realized and implemented.2- and 4-element uniform arrays of the proposed antenna are designed to match to 50-ohm lines.Then the designed antenna is constructed and measured. Simulation results for a single element ,and 2- and 4-element arrays are presented and comparedwith measurement results.To design the large array antenna, aTaylor non-uniform current distribution is proposedto have a low side lobe level. Finally, the general approach to design the whole array antenna, which is to approximate the ideal distribution to use modular design, is presented. Keywords: Microstrip antenna, Wideband, U-shaped slot, Proximity coupling feed.