Patent ID: 7071884

Claim:
An antenna system of a radio communication terminal comprising: an antenna that transmits and receives a communication signal to and from a communication node; a sending end amplifying/filtering unit that amplifies and filters the communication signal to be transmitted through a duplexer; a receiving end amplifying/filtering unit that amplifies and filters the communication signal received through a duplexer; a closed loop control circuit that generates a control signal according to power of a communication signal output from sending end amplifying/filtering unit; and a bias unit that separated the communication signal and a power transmitted from a radio communication terminal through a transmission line, wherein the receiving end amplifying/filtering unit includes a variable amplifier that amplifies a reception communication signal as much as a variable gain according to a control signal, and wherein the closed loop control circuit comprises: a coupling unit that branches a transmission output from a final end of the sending end amplifying/filtering unit; and a detection controller that generates a control signal according to a strength of power of the branched transmission output and applying the control signal to the variable gain amplifier.