Envelope Tracking Comes of Age on Mobile Handsets

摘要

The high value of scarce cellular radio spectrum and demand for ever higher data rates have spurred a great deal of innovation in optimizing mobile radio links, primarily by increasing signal bandwidth and modulation complexity. The consequences for RF transmitter power amplifiers (PA) are increased average output power and higher peak-to-average-power ratios (PAPR), which mean lower PA efficiency and disproportionately high power consumption. For mobile handsets, transmitter efficiency and battery life are not only reduced, but overheating becomes an issue as mobile PA footprints shrink and filter losses mount with new band interoperability and carrier aggregation requirements. Base station transmitters have long had the luxury of a stable antenna environment, complex support electronics, digital processing techniques and envelope tracking (ET). ET has become viable for mobile devices and is now appearing in products. Given BlackBerry's years of internal and collaborative research in mobile radio, this article concentrates on ET for mobile LTE handsets. It also applies to any high PAPR transmitter used with WCDMA, HSPA, DTV and Wi-Fi.