A 5.2-GHz Area-Efficient RF Front-End with 2.79x PAE Enhancement at 7.7-dB Power Back-Off

This work presents an area-efficient fully integrated differential RF front-end at 5.2 GHz using a single-pole-double-throw T/R switch, a LNA, and a dual-power mode PA. The dual-power mode PA significantly improves the power back-off PAE by a factor of 2.79 from the high power mode to the low power mode, and only one transformer is required to realize the different optimum impedance conditions for the PA. The high power mode of the PA achieves 20.7 dBm
$\mathbf{OP}_{1dB}$
and 24.9 dBm
$\mathbf{P}_{sat}$
, while the low power mode achieves 13.8 dBm
$\mathbf{OP}_{1dB}$
and 17.2 dBm
$\mathbf{P}_{sat}$
. The proposed dual-power mode PA meets the emission mask of 54 Mb/s IEEE WLAN 802.11a standard with -25 dB EVM in both operation modes. The proposed LNA achieves a gain of 15.9 dB and a NF of 3.8 dB in 90-nm CMOS technology.