The invention relates to a plug-in adaptive antenna system and to the operating method thereof, which enables an adaptive intelligent antenna to be plugged into (plug & play), i.e. compatible with, any base station operator (e.g. a UMTS B-node) in mobile communications. The inventive method and system consist of processes that are performed in respective synchronism, modulation/demodulation and adaptive processing means, comprising a calculation of aggregate weights (weighted) and beam shaping for both the uplink and the downlink, as well as parameter initialisation and time and power compensation processes, in order to render said method or system transparent to the base station (30). The aforementioned shared weight calculation and beam shaping processes are accompanied by complementary steps consisting in estimating the directions of arrival and obtaining the time delay for each user, in order to locate the users of mobile terminals.