Method and arrangement for correcting phase error in linearization loop of power amplifier

Abstract

A method and arrangement for correcting a phase error in a linearization loop of a power amplifier, the loop comprising an I/Q modulator (10), one or more delay-causing power amplifiers (13) to be linearized, an I/Q demodulator (11) for generating I and Q feedback signals from the output signals of the amplifier (13), difference means (20, 21) of the I and Q branches for generating 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 (14), and a phase shifter (17), the method comprising determination of a phase error resulting from the delay produced in the linearization loop, which determination comprises feeding excitation signals to the I and Q inputs (I_IN, Q_IN) of the linearization loop, measuring the signals resulting from the excitation signals and calculating a 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 a phase shifter (17), whereby on determining the phase error the signals resulting from the excitation signals are measured from the I and Q difference signals or the I and Q input signals of the I/Q modulator (10) and the phase determination is performed while the linearization loop is closed.

Description

Technical field [0001] The present invention relates to amplifiers, and in particular to a method and equipment in linearized power amplifiers. Background technique [0002] Linear amplifiers are used, for example, in modern digital wireless communication systems, because the frequency of the signal to be transmitted must not be extended beyond the actual effective frequency band. The spread of the frequency spectrum originates from the nonlinearity of the amplifier, which causes, for example, adjacent channel interference. The linearity of the amplifier stages depends on how they are biased. They can be divided linearly: Class A amplifiers are the most linear but have poor efficiency, while Class C amplifiers have high efficiency, but they are also highly nonlinear. In power amplifiers, high efficiency is a very important feature, which is especially important in wireless communication devices with limited battery capacity. Therefore, use high-efficiency but non-linear amplifier...

AI Technical Summary

Problems solved by technology

This method has the disadvantage that the loop must be interrupted during the measurement, thus requiring switches on both feedback branches

A drawback of this method is that, for example, when the amplifier is turned on, the linear loop may become unstable, resulting in spectral spread

Phase shifter discontinuities can also cause implementation problems

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