Cellular Handsets: increasing battery life and reducing RF subsystem cost

The problems facing designers of RF subsystems for handsets are very challenging. The need to simultaneously support different systems (LTE, WiMAX, WCDMA, HSPA, MC-GSM etc.) in one handset, whilst supporting and increasing the number of frequency bands, is driving a significant increase in RF system complexity. At the same time, battery life is a major issue on handsets and will become worse with new systems, driven by higher uplink speeds and always-on connectivity.

The traditional approach to these challenges has been to use a number of separate PAs (maybe up to 8 in current designs) within the handset RF subsystem, each covering a fairly narrow band, and optimised for peak efficiency for that band and the system being supported. This works well when only a few frequency bands are required, but quickly becomes very complex for multi-band, multi-mode handsets, with RF switching and thermal issues all making a compact, cost-effective solution extremely difficult to achieve.