A highly efficient watt-level SiGe BiCMOS power amplifier with envelope tracking for LTE applications

In this paper, a pseudo-differential power amplifier (PA) is designed using two SiGe power cells fabricated in the 0.35-μm IBM 5PAe SiGe BiCMOS technology with through-wafer-vias (TWVs). In the continuous wave (CW) measurement, the PA achieves a 2-watt level saturated P_OUT with power-added-efficiency (PAE) above 65% across the bandwidth of 0.7-1 GHz. The envelope tracking (ET) technique is then applied to the PA for enhanced efficiency using the LTE 16QAM signals with a peak-to-average-ratio (PAR) of 7.5 dB. Beside a conventional single buck converter based envelope modulator (SBEM), a dual buck converter based envelope modulator (DBEM) is also designed for higher power drivability. Measurement shows the ET-PA systems can transmit linear P_OUT of 25/24 dBm with system PAE of 40%/32% at 750 MHz for LTE 16QAM 5/20 MHz signals.