Patent ID: 6639950
Filing Date: 2003-10-28
Classification: H03D,H03F

Abstract:
A method for correcting a phase error in a linearization loop of a power amplifier, the loop comprising an I/Q modulator, one or more delay-causing power amplifiers to be linearized, an I/Q demodulator for producing I and Q feedback signals from the amplifier output signal, difference means of the I and Q branches for producing I and Q difference signals from the I and Q feedback signals and the I and Q input signals, the I/Q modulator and the I/Q demodulator receiving an oscillator frequency from the same local oscillator, and a phase shifter, the method comprisingdetermination of a phase error resulting from delay produced in the linearization loop, which determination comprises feeding excitation signals to the I and Q inputs of the linearization loop, measuring the signals resulting from the excitation signals and calculating the phase error by means of the measured signals and excitation signals, and correcting the phase error by adjusting a phase of a local oscillator signal passing to the I/Q modulator or I/Q demodulator by means of the phase shifter, characterized in that when determining the phase error, the signals resulting from the excitation signals are measured from the I and Q difference signals or from the I and Q input signals of the I/Q modulator and that the phase error determination is performed while the linearization loop being closed.