Nonlinear distortion cancellation in OFDM systems using an adaptive LINC structure

The linear amplification using nonlinear components (LINC) technique is a well-known power amplifier linearization method to reduce out-of-band interferences in a nonconstant envelope modulation system, such as the OFDM modulation. The major drawback of LINC transmitters is the inherited sensitivity to gain and phase imbalances between the two amplifier branches. In this paper a novel adaptive full-digital base band method, which corrects any gain and phase imbalances in LINC transmitters mainly due to the un-matching between two branches, is described. Its main advantage is the ability to track the input signal variations and adapt to the changes of amplifier nonlinear characteristics. Other effects are included in the analysis such as quadrature modulator and demodulator impairments. A computer simulation has been carried out to verify method functionality.