Power Envelope Tracking for Mobile Power Amplifiers

This story has been happening as the demand for high-speed data increases and battery capacity has not matched advances with communications technology. It’s not the battery at fault but the technology needed to power the amplifier on the phone. For years, normal DC-DC converters managed the battery power flowing in the phone to different chips. This included the power amplifier (PA) for driving the cellular signal back to the base station, which worked fine when the peak-to-average power ratio (PAPR) was relatively small for 2G and 3G signals. As the technology has progressed from GSM to GPRS to WCDMA to HSPA, the PAPR has increased progressively. Now LTE or 4G has a much higher PAPR that impacts the draw of power from the phone. In Figure 1 you can see this progression of technology for a typical PA output based on a given power input from a device battery.