High efficiency hybrid EER transmitter for WCDMA application using optimized power amplifier

We have developed a “hybrid” envelope elimination and restoration (EER) transmitter using power amplifier (PA) which is optimized for high efficiency of the EER operation. Because the PA operates mostly at the average power region of a modulation signal, the efficiency of the PA at the average drain voltage is very important for the overall transmitter efficiency. Accordingly, the efficiency of the PA has been optimized at the region. A saturation amplifier, class F
^-1
, is built using a 5-W PEP LDMOSFET for forward-link single-carrier wideband codedivision multiple-access (WCDMA) at 1-GHz. For the interlock experiment, the bias modulator has been built with an efficiency of 68.3% and peak output voltage of 31.8 V. The overall efficiency of the transmitter with a conventional PA has been achieved 36.08% at an output power of 29.42 dBm with a power-added efficiency (PAE) of 30.12%. On the other hand, the transmitter with the proposed PA has been achieved an efficiency of 45.34%, improved 9.26%. Besides, the enhanced output power and PAE have been achieved, 32.32 dBm and 39.08%, respectively, with ACLRs of -35.9 dBc at 5-MHz offset. After the linearization using digital predistortion (DFBPD), the ACLR at 5-MHz offset has been improved to -44.8 dBc. These results show that the proposed architecture is a valuable very good candidate for the linear and efficient transmitter.