Apparatus for controlling a gain and phase of an input signal input to a power amplifier, the apparatus comprising: gain control means for controlling the gain of the input signal; phase control means for controlling the phase of the input signal; a gain control loop configured to control the gain control means based on a power level of the input signal and a power level of an amplified signal output by the power amplifier, to obtain a predetermined gain of the amplified signal, wherein the gain control loop is further configured to receive a third signal derived from the input signal and a fourth signal derived from the amplified signal, and compare a power level of the third signal and a power level of the fourth signal and control the gain control means based on the result of the comparison, the gain control loop comprising: a first detector configured to measure the power level of the third signal, and a second detector configured to measure 2. the power level of the fourth signal; and a phase control loop separate from the gain control loop, the phase control loop comprising: a coupler configured to combine a first signal derived from the input signal and a second signal derived from the amplified signal and output an error signal related to a phase difference between the first and second signals, the first and second signals being arranged to have the same power level when the power amplifier is operating at the predetermined gain; a third detector configured to measure a power level of the error signal; and a processor configured to control the phase control means based on the measured power level of the error signal to obtain a predetermined phase of the amplified signal, wherein the phase control loop is arranged to delay the first signal before obtaining the error signal, such that the delayed first signal and the second signal used to obtain the error signal correspond to the same part of the input signal. gain control means for controlling the gain of the input signal; phase control means for controlling the phase of the input signal; a gain control loop configured to control the gain control means based on a power level of the input signal and a power level of an amplified signal output by the power amplifier, to obtain a predetermined gain of the amplified signal, wherein the gain control loop is further configured to receive a third signal derived from the input signal and a fourth signal derived from the amplified signal, and compare a power level of the third signal and a power level of the fourth signal and control the gain control means based on the result of the comparison, the gain control loop comprising: a first detector configured to measure the power level of the third signal, and a second detector configured to measure 2. the power level of the fourth signal; and a phase control loop separate from the gain control loop, the phase control loop comprising: a coupler configured to combine a first signal derived from the input signal and a second signal derived from the amplified signal and output an error signal related to a phase difference between the first and second signals, the first and second signals being arranged to have the same power level when the power amplifier is operating at the predetermined gain; a third detector configured to measure a power level of the error signal; and a processor configured to control the phase control means based on the measured power level of the error signal to obtain a predetermined phase of the amplified signal, wherein the phase control loop is arranged to delay the first signal before obtaining the error signal, such that the delayed first signal and the second signal used to obtain the error signal correspond to the same part of the input signal. a first detector configured to measure the power level of the third signal, and a second detector configured to measure 2. the power level of the fourth signal; and a phase control loop separate from the gain control loop, the phase control loop comprising: a coupler configured to combine a first signal derived from the input signal and a second signal derived from the amplified signal and output an error signal related to a phase difference between the first and second signals, the first and second signals being arranged to have the same power level when the power amplifier is operating at the predetermined gain; a third detector configured to measure a power level of the error signal; and a processor configured to control the phase control means based on the measured power level of the error signal to obtain a predetermined phase of the amplified signal, a coupler configured to combine a first signal derived from the input signal and a second signal derived from the amplified signal and output an error signal related to a phase difference between the first and second signals, the first and second signals being arranged to have the same power level when the power amplifier is operating at the predetermined gain; a third detector configured to measure a power level of the error signal; and a processor configured to control the phase control means based on the measured power level of the error signal to obtain a predetermined phase of the amplified signal, wherein the phase control loop is arranged to delay the first signal before obtaining the error signal, such that the delayed first signal and the second signal used to obtain the error signal correspond to the same part of the input signal.