A relative velocity corresponding to a peak signal is measured by a relative velocity measuring means 103 for a selected signal, and based on this relative velocity the quantity of a change in phase in each time interval capable of coherentprocessing is calculated in a quantity-of-change-in-phase calculation means 104 for the selected signal. ピーク信号に相当する相対速度を選択信号相対速度計測手段103で計測し、この相対速度に基づいてコヒーレント処理が可能な時間間隔毎の位相変化量を選択信号位相変化量算出手段104で算出する。 - 特許庁