On Half-Power Beamwidth of Intelligent Reflecting Surface

Half-power beamwidth (HPBW) is a key parameter to measure the performance of antenna array and newly proposed intelligent reflecting surface (IRS) systems. In this letter, we first establish system model for IRS in uniform linear (ULA) rectangular (URA) configurations, then HPBW both cases are derived under far-field condition without considering channel path-loss fading. We find that ULA URA equal array’s at same reflect/transmit angle with maximal ratio combining applied, while always greater than or when all weights equal. Besides, certain incident angles, there will be abrupt changes analytical expressions boundary values provided. Unlike traditional active array, our conclusion shows change angles. Simulation results verify correctness derivations.