A Dynamically Biased Multiband 2G/3G/4G Cellular Transmitter in 28 nm CMOS

Abstract

We present a highly configurable, low-power, low-area, low-EVM, SAW-less transmitter (TX) architecture that is based on a dynamically biased power mixer. All FDD/TDD bands from 0.7 to 2.7 GHz for 4G LTE Rel-11 and 3G $\bf{HSPA} + $ are supported in addition to 2G quad bands. The power-mixer bias current is dynamically adjusted based on the instantaneous baseband signal swing using a fully-differential hybrid full-wave rectifier/envelope-detector circuit. Dynamic biasing leads to greater than 50% current savings when compared to fixed-biasing while providing a higher output power with better linearity. Implemented in 28 nm CMOS technology, the TX shows better than $- \bf{157}\;\bf{dBc}/\bf{Hz}$ RX-band noise emission and $- \bf{41}\;\bf{dBc}$ ACLR for output powers up-to $+ \bf{4}\;\bf{dBm}$ across all 3G/4G bands, while demonstrating above 80 dB of gain control range. In addition, the TX can be configured to provide better than $- \bf{65}\;\bf{dBc}$ CIM3, allowing it to meet stringent spurious emission specifications when transmitting 1 RB 4G LTE signals in B13/B26/B1.