Patent ID: 7450067

Claim:
A method for estimating the number of incoming radio waves by an array antenna in which a plurality (=M) of antenna elements are linearly arrayed with a same element spacing, and estimating the number of said incoming radio waves, comprising the steps of: calculating correlations between a receive signal of each antenna element and receive signals of all antenna elements of said array antenna to form an M×M array covariance matrix; creating a correlation matrix by: removing a diagonal element from a predetermined row or column of the covariance matrix; extracting a predetermined p number of correlations from (M−1) number of correlations after said diagonal element is removed to form a first row of the correlation matrix; and sequentially shifting one element at a time to form subsequent rows of the correlation matrix; creating an estimation matrix using said correlation matrix; and the estimating the number of incoming radio waves based on each row element of an upper triangular factor matrix obtained by performing QR decomposition on said estimation matrix.