Aspects of the present disclosure take advantage of a prism-like effect that occurs in a Reconfigurable Intelligent Surface (RIS), where the RIS reflects incident signals of different frequencies in different directions. for determining characteristics of a channel between a transmitter and a receiver wherein the channel includes the RIS. In particular, this may include estimating an angle of arrival (AoA) to the RIS in uplink transmission or the angle of departure (AoD) from the RIS in downlink transmission. Aspects of the present disclosure also provide solutions to compensate the prism effect for wideband transmission, especially at high frequencies (e.g. mmWave and THz).