A LINC-based polar transmitter with reduced envelope bandwidth for wideband communications

Abstract

This paper presents a polar transmitter with reduced envelope bandwidth and the linear amplifier with nonlinear components (LINC) technique is used to produce constant-envelope signals according to the remaining envelope information. This architecture relaxes the bandwidth requirement for the traditional envelope modulators. Only the low-frequency part of the envelope signal is amplified to provide power supply for the power amplifier (PA) stage. In the LINC path, the remaining envelope information is modulated into the phase signals, which are used as the radio frequency (RF) input to the nonlinear PA pair. At the RF output, the envelope information is retrieved from these two parts by the supply-modulated PA pair. The simulation results show that the envelope bandwidth is reduced to around one third of the original bandwidth by the proposed technique. For 2-level LINC structures, the combining efficiency of the proposed architecture is improved to more than twice as the one of LINC-only structure since the combining angles are reduced.