A Current-Mode Multi-Phase Digital Transmitter With a Single Footprint Transformer-Based Asymmetric Doherty Output Network

This article introduces a current-mode multi-phase digital transmitter with single footprint transformer-based asymmetric Doherty output network. The proposed architecture overcomes the bandwidth expansion associated polar power amplifier (PA), while still achieving relatively constant and drain efficiency profiles. Additionally, to achieve enhancement in deep back-off (PBO), simultaneously compact form-factor, an series matching network using transformer-within-transformer structure is also proposed. A proof-of-concept eight-phase implemented general-purpose 65 nm CMOS process. achieves more than 20 dBm (Pout) 31% (DE) from 4.5 GHz 6.7 GHz. At 8 dB PBO, it DE of 23% 24% at 6.5 7.0 GHz, which corresponds 1.76× 1.93× improvement compared normalized class B PA, respectively. 21% average Pout 14 r.m.s. error vector magnitude (EVMrms) 4.1% for MSym/s 64-QAM waveform