A switched-capacitor controlled digital-current modulated class-E EER transmitter

An envelope elimination and restoration (EER) transmitter that comprises a class-E power amplifier and a digitally controlled current DAC modulator is presented. A switched capacitor DAC is designed to control an open-loop transconductor that operates as a current modulator, modulating the amplitude of the current supplied to a class-E PA. Such a topology allows for increased filtering of the quantization noise that is problematic in most digital PAs (DPA). The system measurements yield a peak output power and power added efficiency (PAE) of 22.5 dBm and 23.6%, respectively. When applying a WCDMA signal, the measured EVM is 1.32% and the adjacent channel power ratio (ACPR) is -37.9 dBc, while outputting 19.9 dBm at 14.3% PAE. For an LTE signal, the measured EVM is 3.72% and the ACLR is -30.2 dBc, while outputting 18.1 dBm at 10.6% PAE.