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 (GSM, WCDMA, HSPA, LTE etc.) in one handset, whilst supporting an increasing 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.
Application of Nujira Technology
Nujira's High Accuracy Tracking (HAT™) technology allows high PA efficiencies to be achieved with broadband PAs capable of supporting many different modulation types, and thus allows a fundamental re-thinking of the RF sub-system architecture. Cost effective broadband PAs are a key enabling technology for 4G handsets.
The Nujira Power Modulator function is integrated within the RF PA module which now contains just one or two broadband PAs to cover all the frequency ranges required. The drain voltage of each PA is dynamically varied in line with the modulation envelope, thus ensuring that the output device operates in near-compression (even at low output powers), and resulting in very high PA efficiency. The modulation envelope is derived from the digital (modulation) signal from the baseband system.
Benefits
Applying Nujira's HAT™ technology to handsets results in higher power efficiency, with a 50% reduction in PA power for the same RF output - leading to longer battery life and lower heat dissipation (especially for new standards such as HSUPA, LTE and WiMAX).
In addition, the technology enables a significant reduction in RF system architectural complexity, with fewer broadband PAs doing the work of many individual PAs - leading to reduced PA module cost and size. Nujira's HAT™ technology is thus an essential enabler for future multimode, multiband handsets.