If this judged results in NO, the number of running averages of an autocorrelation matrix of a reception signal is increased and the order of the autocorrelation matrix is reduced, or alternatively, the number of estimated wave sources in a signal spatial matrix obtained by characteristic value- characteristic vector expansion of the autocorrelation matrix after the running average is reduced by one. この判定でNOの場合には、受信信号の自己相関行列についての移動平均の回数を増やし、自己相関行列の次数を減少させるか、または移動平均後の自己相関行列を固有値・固有ベクトル展開して得た信号空間行列における推定波源数を1つ減らす。 - 特許庁