Optimum tilt for elevation-scanned phased arrays

It is shown that, subject to certain restrictions, the optimum tilt angle can be calculated as a function of only the highest beam elevation angle. The term optimum means the condition that the antenna gain at the horizon is maximum. The restrictions are that the antenna be operated outside the grating-lobe regime for all required scan angles and that scan angles greater than 60 degrees off broadside by avoided to allow useful operation of the radar system (considering antenna impedance match, sidelobes, gain, and beam width). It is assumed that the antenna, in principle, can be impedance matched to any elevation angle, leaving the match at broadside as a special case, without particular advantages. The results indicate that for most practical requirements (high-beam elevation between 45 degrees and 70 degrees ) the optimum tilt angle should be around 20 degrees to 30 degrees .<>