Implementation and simulation of the impact of mixer phase mismatch in cartesian feedback linearization systems

The Power Amplifier (PA) is a Radio Frequency (RF) circuit and its main goal is to drive the transmitter's (Tx) antenna. It faces a trade-off between spectral efficiency and power saving. Therefore, different linearization methods are proposed to increase linearity while optimizing power consumption. Digital Cartesian Feedback (CFB) presents itself as a good linearization system when using narrowband signals in portable or mobile devices. The main drawback with this implementation are the nonlinearities present on the feedback path. This work's main contribution is the analysis, simulation and correction of phase mismatch between forward and feedback paths. Firstly, implementation showed the impact of phase mismatch through spectrum side lobe increase. Next, phase mismatch is introduced in simulation along with a Phase Correction (P.C.) block. Finally, results show comparison between phase mismatch and performance degradation. The performance is measured through spectrum side lobes, RMS EVM and constellation plot. The results outlines not only the advantage of using CFB linearization in systems that presents phase mismatch, but also, how the P.C. can improve frequency response and EVM even further.