Reconfigurable 2.4/5.0-GHz Dual-Band CMOS Power Amplifier for WLAN 802.11ax

This paper presents a reconfigurable 2.4/5-GHz dual-band power amplifier (PA) for WLAN 802.11ax application. The PA employs a series-combining transformer (SCT) in the output matching network to deliver high output power. To extract high passive efficiency of the output matching network both in the 2.4- and 5-GHz bands, a new efficiency-oriented design methodology of reconfigurable dual-band output matching network is proposed. Besides, the reconfigurable dual-band inter-stage matching network using power splitting structure is introduced. Based on the proposed methodology, the PA is designed and fabricated in 40-nm CMOS technology, and the passive efficiencies of the implemented output matching network are 70.3% and 73.8% at 2.4 and 5.5 GHz respectively. For continuous-wave, the proposed PA achieves a saturated power ( $\text{P}_{\mathrm {sat}}$ ) of 25.4 and 24.4-24.8 dBm with power-added efficiency (PAE) of 25% and 20.8-27.3% in the 2.4- and 5-GHz WLAN bands, respectively. The proposed PA outperforms other reconfigurable dual-band or multi-band PAs in terms of the efficiency. When testing with 802.11ax signal with 1024-quadrature amplitude modulation (QAM), a -35-dB error vector magnitude (EVM) specification can be satisfied in the 2.4- and 5-GHz bands.