Abstract: A correlation energy detector detects a magnitude of a correlation between a first signal series (Ii, Qi) described by I-Q orthogonal components and a predetermined second signal series (HJ). The correlation energy detector includes a correlation computing section for computing correlation values (Iij, Qij) between the first signal series (Ii, Qi) and the predetermined second signal series (HJ), and a root computing section for computing {{square root over ( )}(Iij2+Qij2)} as a root value of a sum of squares of the correlation values (Iij, Qij) obtained from the correlation computing section.