A Cartesian loop transmitter with DC offsets adjusted in training slots

摘要

The I and Q DC offsets in an RF modulator and transmitter may drift in use. To counteract this drift baseband ramp training signals are applied sequentially to in-phase and quadrature channels during training slots so that RF output minima maybe located by use of detector 135. Updated DC offsets are then applied in operation by DSP 101. The Cartesian loop 106 is disabled during training. The transmitter may be for TETRA systems.