Multiphase Interpolating Digital Power Amplifiers for TX Beamforming

Zhidong Bai, Wen Yuan, Ali Azam, Jeffrey S. Walling
2022 Chips  
This paper presents a four-channel beamforming TX implemented in 65 nm CMOS. Each beamforming TX is comprised of a C-2C split-array multiphase switched-capacitor power amplifier (SAMP-SCPA). This is the first use of multiphase interpolation (MPI) for beam steering. This technique is ideal for low-frequency beamforming and MIMO, as it does not require passive or LO-based phase shifters. The SCPA is ideal for use as the core element since it can perform frequency translation and data conversion,
more » ... nd drive an output at high power and efficiency in a compact die area. A prototype four-element beamforming TX, occupying 2mm×2.5mm, can achieve a peak output power of 24.4 dBm with a peak system efficiency (SE) of 24%, while achieving <1∘ phase resolution and <1 dB gain error. When transmitting a 15 MHz, 64-QAM long-term evolution (LTE) signal it outputs 18.4 dBm at 14% SE with a measured adjacent channel leakage ratio (ACLR) of <−30 dBc and an error vector magnitude (EVM) of 3.27% RMS at 1.75 GHz. A synthesized beam pattern based on measured results from a single die achieves <0.32∘ RMS beam angle error and <0.1 dB RMS beam amplitude error.
doi:10.3390/chips1010004 fatcat:zfsi3zv4xbdtnc3j5jljbigc3q