10.4 A 4×4 Dual-Band Dual-Concurrent WiFi 802.11ax Transceiver with Integrated LNA, PA and T/R Switch Achieving +20dBm 1024-QAM MCS11 Pout and −43dB EVM Floor in 55nm CMOS

The new WiFi 11ax standard carries several improvements compared to its 11g/ac predecessor. It supports multi-user MIMO and uses OFDMA modulation, which enables users to share the same channel via allocated Resource Units (RU). In addition, it provides transmit power adjustments for better operation in a dense environment. Furthermore, the standard calls for the support of MCS11 1024-QAM modulation with target transmit (TX) EVM of -35dB, which results in nearly 25% higher throughput compared to MCS9 256QAM. In order to improve user experience to guarantee signal quality between walls and obstacles, a <; -40dB receive (RX) EVM is required for 1024-QAM signals derived by fading-channel model emulation and field measurements. Such new features have posed stringent requirements to in-band distortion/noise of both TX and RX as well as the TX emission, especially in the RU case (minimum 2MHz) due to higher power density.