A 400MHz Symbol-Power-Tracking (SPT) Supply Modulator With SPT-Adaptive-Biasing Network Supporting 5G FR2 CMOS PA

The 5G new-radio (NR) frequency-range-2 (FR2) for cellular communications supports a maximum channel bandwidth of 400MHz[1] and utilizes orthogonal frequency-division multiplexing (OFDM) to support high data rates with complex modulations such as the quadrature amplitude modulation (QAM). The mm-wave CMOS power amplifiers (PAs) still consume large amounts of power at their average output power due to high peak-to-average ratios (PAPRs). Envelope tracking (ET) has been a candidate for improving the PA's deep power-back-off (PBO) efficiency by adjusting the VDD of the PA (VDDPA) based on the output power level of the PA. The analog envelope tracking supply modulator (AET-SM) enables the ET bandwidth (BW) up to 200MHz[2] but enhancing beyond this range is challenging. Therefore, digital envelope tracking (DET) [3] and symbol power tracking (SPT) [4]–[6] have been suggested to surpass BW bottlenecks.