Optimising the Image Rejection in Phase-Only Multilevel LINC Transmitters

This work presents a process to optimise the image-rejection in phase-only multilevel LINC transmitters (PO-MLINC). The image is generated in the IQ-modulator-based phase-modulators. Compared to optimising the image-rejection for each IQ-modulator separately, it can be further optimised for the full system. To do that, the fact that the level-generating amplifiers of the PO-MLINC are operated within a limited range of input phases is exploited. The theory of this process is presented. Furthermore, simulation and measurement results are shown. The measurement results show a 7.7-dB IMRR improvement in the PO-MLINC setup.