A training method for reducing phase and gain loop imbalances in a Cartesian loop or adaptive predistortion radio transmitter amplifier

摘要

In a training mode, test signals are applied to the I and Q inputs of a linearised transmitter having I and Q feedback channels. Imbalances in the feedback signals are determined by a processor 560, which adjusts the LO phase shifter 582 and then the gain adjuster 590 to reduce phase and gain imbalances between the I and Q loops. The stability and accuracy of the linearised transmitter is improved. The transmitter may be used in a TETRA system.