Ka-band phased array antenna with circular rim

16 × 16 phased array antenna composed of microstrip antipodal tapered slot antenna elements is designed at Ka-band. The array element is designed by using infinite array simulations to approximate the mutual coupling effects to obtain good input match for various beam steering angles in the final array. A circular rim with ground plane is added to the final array to suppress grating lobes appear when the beam is steered. It is shown by simulations that grating lobe is suppressed to a level less than -20 dB at 35 GHz.