Patent ID: 6728520
Filing Date: 2004-04-27
Classification: H04B

Abstract:
An apparatus for controlling a transmit power level of an information signal in an external antenna unit coupled to a hand held device comprising:a logic unit in the hand held device configured to produce a control voltage indicating a transmit power level desired by the hand held device; and a closed loop circuit in the antenna unit configured to receive the control voltage from said logic unit and to adjust the transmit power level of the information signal based on the control voltage, said closed loop circuit further comprising: a power detector for detecting the transmit power level of the external antenna unit; a log amplifier coupled to said power detector, wherein said log amplifier converts the output of said power detector to a digital format to produce a log amplifier output; a control voltage amplifier coupled to said log amplifier, wherein said control voltage amplifier determines whether said log amplifier output is equal to the control voltage, wherein said control voltage amplifier converts said log amplifier output to a voltage format to produce a control voltage amplifier output, and wherein said transmit power level is set equal to said log amplifier output if said log amplifier output is equal to said control voltage; a gain control amplifier coupled to said control voltage amplifier, wherein said gain control amplifier adjusts said control voltage amplifier output if said control voltage amplifier determines that said log amplifier output is not equal to the control voltage, and wherein said gain control amplifier converts said adjusted control voltage amplifier output to a digital format to produce a gain control amplifier output; a filter coupled to said gain control amplifier, to filter said gain control amplifier output; and a power amplifier coupled to said filter, wherein said power amplifier converts the output of said filter to a voltage format to produce a power amplifier output, wherein said power detector is coupled to said power amplifier, and wherein said power detector output is set equal to said power detector input.