1. A cognitive radio system, comprising: a memory which stores a system parameter and a pseudo parameter, the system parameter being used for generation of a feature value specific to a radio system for which a search is performed, the pseudo parameter being similar to the system parameter; a feature value generator which generates one or a plurality of feature values based on a signal in a received frequency band by using the system parameter; a non-feature value generator which generates one or a plurality of non-feature values based on the signal in the received frequency band by using the pseudo parameter; and a determination section which determines whether or not a signal of the radio system exists by using the one or the plurality of feature values and the one or the plurality of non-feature values.