A Time-Mode-Modulation Digital Quadrature Power Amplifier Based on 1-bit Delta-Sigma Modulator and Transformer Combined FIR FIlter

This paper proposes a Time-Mode Modulation (TMM) digital quadrature power amplifier (PA), which can realize high efficiency at power back-off (PBO) by applying the proposed 1-bit DSM and transformer (XFMR) combined FIR filter. The 1-bit Delta-Sigma Modulator (DSM) and digital mixer encode the input into a 2-level intrinsically linear on/off signal for TMM operation. The XFMR combined FIR filter suppresses the DSM quantization noise to avoid efficiency degradation and is insensitive to delay mismatches. The TMM PA is fabricated in 65 nm CMOS. Without digital pre-distortion (DPD), it achieves 26.4% efficiency with 40MS/s 64-QAM at 2.6GHz and supports 256-QAM.