A Compact Dual-Band Digital Polar Doherty Power Amplifier Using Parallel-Combining Transformer

This paper presents a dual-band high-power digital polar Doherty power amplifier (PA). A current-mode parallel-combining transformer (PCT) power combiner is introduced for Doherty operation, which realizes simultaneous dual-band coverage, high output power, and backoff efficiency enhancement with an ultra-compact single-transformer footprint. The PA is implemented in 55-nm CMOS and occupies 1.11 mm2 die area. It achieves 28.9-dBm peak Pout with 36.8% PAE in low band (LB) and 27.0-dBm peak Pout with 25.4% PAE in high band (HB). For 12-subcarrier 180-kHz bandwidth cellular narrowband Internet-of-Things (NB-IoT) signals, the peak Pavg of 24.4 dBm with average PAE of 29.5% at 850 MHz and the peak Pavg of 23.0 dBm with average PAE of 17.9% at 1.7 GHz are obtained with -21.6-dB error vector magnitude (EVM). Moreover, the PA achieves 20.8-dBm Pavg, 22.7% average PAE, and -30.5-dB EVM for 20-MHz 256-QAM WLAN signal.