32.1 A 47GHz 4-way Doherty PA with 23.7dBm P<sub>1dB</sub> and 21.7% / 13.1% PAE at 6 / 12dB Back-off Supporting 2000MHz 5G NR 64-QAM OFDM
Xiaohan Zhang, Hao Guo, Taiyun Chi
Abstract
As mm-wave 5G continues to advance in the 28 and 38GHz bands (n257 to n261), the ever-increasing demand for data-rates is also driving 5G expansion to higher frequencies, such as the 47GHz band (n262) and V band (n263). In these bands, achieving high energy efficiency remains a critical design challenge, especially for wideband 5G NR OFDM signals with 10-to-12dB PAPR and up to a 2000MHz channel bandwidth (as introduced in 3GPP V17.6.0). Multiway Doherty PAs [1–3] and LMBAs [4] have been explored to enhance efficiency at deep power back-off (PBO). Beyond component-level demonstrations, Doherty PAs have also been integrated into TRX front-ends [5] and phased arrays [6] to enhance the overall TX efficiency. Figure 32.1.1 (top left) compares the efficiencies of N-way Doherty PAs with N = 2 to 4, assuming their output networks are designed using 90° Tlines with a practical Tline loss. From this simplified analysis, a 4-way Doherty PA achieves $1.44 \times$ power saving over a 2-way Doherty PA when amplifying an OFDM signal with a 12dB PAPR.