A Quadrature-Rotation Phased-Array Transmitter with 15-Bit Phase Tuning and 0/3/6/9/12/15-dB PBOs Efficiency Enhancement

In this paper, a 4-element digital-modulated phased-array transmitter (TX) based on quadrature switched/ floated-capacitor power amplifiers (SFCPAs) and reconfigurable switched-capacitor tuning lines (RSCTLs) is proposed. Phase shifting in each element is achieved by hybrid coarse and fine phase-tuning techniques. The SFCPAs with quadrature rotation is presented for coarse phase tuning, while the RSCTLs is used for fine phase tuning. To improve the efficiency at deep power back-off (PBO) peaks, a 4-to-1 reconfigurable transformer is introduced in the SFCPAs. Meanwhile, a 1-by-4 active power divider is utilized for isolation improvement among each elements. The proposed phased-array TX is implemented in conventional 40-nm CMOS technology. The fabricated phased-array TX features 28.4dBm peak output power and 37.9% peak system efficiency. In addition, it supports 0/3/6/9/12/15-dB PBOs efficiency enhancement and 15-bit phase-tuning resolution.