A Current-Mode, Low Out-of-Band Noise LTE Transmitter With a Class-A/B Power Mixer

A complete SAW-less transmitter meeting LTE requirements is presented. High power efficiency and low out-of-band noise are obtained exploiting fully current operation of an analog baseband followed by a class-A/B power mixer. Out-of-band emissions are limited by filtering noise and DAC replicas right before the signal up-conversion through a current-mode Biquad feeding directly the power-mixer. The transmitter, implemented in 55 nm CMOS technology, shows -158 dBc/Hz RX-band noise emission at 30 MHz offset for LTE10, while consuming 96 and 34 mW from the single 1.8 V power supply at 4 and -10 dBm output power, respectively. ACLR is always below -42 dBc up to 4 dBm for both LTE10 and LTE20.