1. A receiver apparatus for receiving incoming waves which are radio waves that arrive at an array antenna including a plurality of antenna elements, the receiver apparatus comprising: a plurality of radio receiver units that generate a plurality of digital signals corresponding to a plurality of signals, on a basis of the plurality of signals received via the plurality of antenna elements; a processor; and a memory storing a program which, when executed by the processor, performs a process including, estimating a plurality of first electric-power delay profiles corresponding to the plurality of digital signals, on a basis of the plurality of digital signals; generating a synthesized electric-power delay profile by synthesizing the plurality of first electric-power delay profiles; changing a direction of a null point of the array antenna and generating an array process signal by performing an array process for the plurality of digital signals by directing the null point in the changed direction; estimating a second electric-power delay profile from the array process signal; generating a difference electric-power delay profile obtained by subtracting the second electric-power delay profile from the synthesized electric-power delay profile; creating a two-dimensional map indicating a relationship between delay times and arrival angles of the incoming waves, on a basis of the difference electric-power delay profile and the changed direction of the null point; and outputting an arrival angle of a component having a shortest delay time and a largest electric power, among the incoming waves on the two-dimensional map.