The object of the present disclosure is an active positioning system for positioning at least one mobile device (100) by utilizing radio frequency technology, the positioning system comprising at least one essentially stationary fixed base station (101) i.e. an active positioning system antenna (101), and an electronics unit (106) i.e. a transceiver of the antenna (101), which transceiver comprises at least one antenna for transmitting signals comprising at least position information to at least one mobile device (100), which position information of the signals comprises information on an effect area of the antenna (102, 104) by using certain transmit power. The active positioning system comprises as the mobile device a TAG (100), which is fixed to the user or application of the TAG directly or indirectly, an electronics unit (106) of the base station (101), at least one antenna (102, 104) directed to different sections of a controlled area. The active positioning system antenna (101) receives said transmitted at least one signal of the formed measurement signals and information signals, and the positioning system antenna (101) comprises control means to control transmit power of said at least one antenna based on at least one signal of the formed measurement signals and information signals received at least by the base station for performing information processing of the mobile device position i.e. the TAG position at least based on transmit power level.