Abstract: A base transceiver station with active antennas in a CDMA mobile communication system, comprising a transceiver installed indoors for up-converting a CDMA-modulated signal to be transmitted to a service subscriber and down-converting a signal received from the subscriber into an intermediate frequency signal, a divider installed indoors for dividing a forward channel signal from the transceiver into a plurality of sector-unit forward channel signals, a coupler for coupling a plurality of sector-unit reverse channel signals and transferring the resultant signal to the transceiver, an antenna interface unit installed indoors for appending a DC voltage to each of the sector-unit forward channel signals from the divider, transferring the resultant sector-unit forward channel signals to a Butler matrix, receiving the sector-unit reverse channel signals from the Butler matrix and transferring them to the coupler, and an active radio frequency module installed outdoors for radiating each beam forming signal from the