Compensation of path imbalance in LINC transmitters using EVM and ACPR look up tables

This paper presents a simple compensation scheme that can be used for adjustment of gain and phase imbalances in linear amplification with nonlinear components (LINC) transmitters. Complex baseband equivalent signals and systems are considered to analyze error vector magnitude (EVM) and adjacent channel power ratio (ACPR) of the transmitter. A digital signal component separator (SCS) with a baseband digital signal processor (DSP) using look up tables (LUT) for EVM and ACPR is proposed to compensate gain/phase imbalances of RF paths in the LINC transmitter. The suggested method is simple to implement and can be applied without using calibration signal. The proposed SCS is implemented and the suggested scheme is verified by showing the 9.5dB ACPR improvement for 16-QAM signal.