To improve estimation precision even in environments such as a closed environment, an underground shopping area and the like causing a multipath to occur therein.
An apparatus is provided to estimate at its receiver side a direction in which an electric wave comes from a transmitter. The apparatus comprises: a selecting means which receives the electric wave having a plurality of frequencies from the transmitter, measures values of amplitude and phase of received signals at respective frequencies, and selects one or more frequencies being less affected by a multipath component from a measurement result; and a judging means that monitors phase changes in the received signal at the selected frequencies taking place along with movements of the receiver, and judges a movement direction as the direction of the incoming wave in which the amount of the phase change is maximum.
OKUBO SHINZO
FURUSAWA SUKEYUKI
NAKAJIMA NOBUO
UNIV ELECTRO COMMUNICATIONS