A 24-to-32GHz series-Doherty PA with two-step impedance inverting power combiner achieving 20.4dBm Psat and 38%/34% PAE at Psat/6dB PBO for 5G applications

Abstract

Line-of-sight millimeter-wave (mm-wave) 5G phased array systems are key solutions to overcome the free-space path loss while providing a multi-Gbit/s data throughput. To realize these systems, nanoscale CMOS technologies should be exploited to enable high integration, compact area, low cost, and high yield. Besides, 5G systems typically employ spectrally efficient complex modulation schemes with high peak-to-average power ratios (PAPRs), which demand the transmitter (TX) power amplifier (PA) to operate in power back-off (PBO), thus degrading its average efficiency. Many techniques such as outphasing [1,2], load-modulated balanced amplifiers (LMBAs) [3–4], and Doherty PAs (DPAs) [5–9] are adopted in mm-wave TXs to enhance efficiency at PBO. Among them, the Doherty is an “RF-in RF-out” PBO efficiency enhancement topology supporting signals with large modulation bandwidth. These mm-wave DPAs are inherently narrowband structures due to employing a lumped-element quarter-wave transmission line (QTL). Thus, the broadband operation is only feasible by increasing the complexity of the Doherty power combiner, compromising with its passive efficiency [7–8]. Also, in these architectures, their optimum PAE at PBO is still narrowband while providing broadband P1dB.