Patent ID: 8331882

Claim:
A power amplification circuit comprising: a power supply including a variable supply voltage and a supply current; a power amplifier configured to receive a communication signal and the variable supply voltage from the power supply, and to output an amplified communication signal; an antenna coupled to the output of the power amplifier; a current sensing circuit coupled between the power supply and the power amplifier, wherein the current sensing circuit is configured to measure the supply current from the power supply to the power amplifier; a memory configured to store a look-up table including at least a nominal supply current, a correction value and a new supply voltage; and a control circuit configured to adjust the variable supply voltage provided by the power supply according to an amount and direction of a load impedance shift of the power amplifier, to a level such that a product of an input supply voltage and a measured input current equals a determined input power level, the amount and direction of the load impedance shift being determined based on whether the measured supply current is greater than or less than the nominal supply current retrieved from the look-up table, the input supply voltage is calculated by applying the correction value to the new supply voltage, the correction value corresponds to the difference between the measured input supply current and the retrieved nominal supply current, the new supply voltage corresponds to the measured input supply current, thereby normalizing an output power level of the amplified communication signal at a constant value.