A Hybrid Polar-LINC CMOS Power Amplifier With Transmission Line Transformer Combiner

This paper demonstrates the implementation of a hybrid polar linear amplification with nonlinear components (LINC) power amplifier (PA) that uses the combination of polar and LINC schemes. The hybrid polar-LINC operation is based on the idea of representing envelope information with the combination of the two schemes. The high bandwidth burden of a supply modulator in a polar transmitter can be effectively relieved, and the back-off efficiency of a LINC transmitter is improved. The implementation is accomplished with a CMOS PA and a CMOS supply modulator. The designed PA includes a class-E amplifier and the proposed output combiner, which is based on a transmission line transformer with isolation resistors. Since the combiner keeps the operating condition of PAs intact regardless of the phase differences, out-phased signals for LINC can be linearly combined. The implemented hybrid polar-LINC architecture, including the PA and a supply modulator, has a 28.5-dBm maximum linear power and 29.6% efficiency without any pre-distortions.