Impact of the number of levels on the performance of multilevel LINC transmitters

This paper analyses an energy-efficient multilevel LINC transmitter with low complexity. Compared with a conventional multilevel LINC using a supply modulator, a new architecture to realise multiple levels is analysed. With this architecture, distortion caused by delay mismatch and memory effects caused by the limited bandwidth of PAs can be mitigated resulting in improved out-of-band emissions. A system analysis shows the improvement of performance regarding efficiency, spectrum and ACLR in presence of delay mismatch and system bandwidth limitations. The analysis at system level is verified by measurements complying with 3GPP LTE specification. An improvement of 17 dB in out-of-band emission is observed by increasing the number of levels from 1 to 40. Meanwhile, average efficiency is also increased from 12 % to 42 %.