21.4 An LTE-A Multimode Multiband RF Transceiver with 4RX/2TX Inter-Band Carrier Aggregation, 2-Carrier 4×4 MIMO with 256QAM and HPUE Capability in 28nm CMOS

With the increasing popularity of social media, artificial intelligence (AI) and mobile computing, higher data-rate wireless communication is required. In the existing limited 4G spectrum, 3GPP standards have defined several methods to increase the data-rate, e.g., carrier aggregation (CA), high-order modulation (HOM) and MIMO technique; however this comes at the cost of extra power consumption and potential sensitivity degradation due to the spurious components generated by CA. In addition, high-power user equipment (HPUE) extends the coverage range and uplink throughput, but introduces more stringent linearity requirements for transmitter design. In this work, we present a 28nm CMOS LTE-A transceiver, capable of supporting up to 4 inter-band downlink (or 2-carrier $4 times 4$ downlink MIMO) and 2 inter-band uplink CA concurrently while adopting ADPLLs for RX and TX with 256-QAM capability. The techniques adopted to achieve these features are described in this paper.