Envelope tracking techniques

The growing demand for high data rate cellular systems has pushed the adoption of 4G/5G Long-Term Evolution (LTE) which uses high peak-to-average power (PAPR) modulation schemes. 5G will bring high data capacity and low latency using the sub-6 GHz and mm-wave spectrum. The increased adoption of powerful worldwide smart phones has been in part possible due to increase of CMOS technology in lower feature nodes as FinFET 7 nm/14 nm. This has made possible the adoption of “old” techniques such as envelope tracking (ET) into smart phones. The ET technique was mentioned back in 1952 by Leonard R. Kahn who introduced a related technique, envelope elimination and restoration (EER). Envelope tracking improves the linearity and efficiency RF for power amplifiers, typically the most power-hungry components in a wireless transmitter. With explosive band proliferation as well as the use of carrier aggregation (CA) and multiple input multiple output (MIMO) techniques, the research area of improving the cost, size, and the performance of the RF transmit solution is very active.