60GHz transmitter front-end in 40nm LP-CMOS with improved back-off efficiency

A three-stage, transformer-coupled class-AB power amplifier (PA) and a super source-follower-based I-Q upconversion mixer are implemented in 40nm LP-CMOS technology. The transmitter (Tx) front-end is designed for multi-Gbps QPSK/QAM-16 signal transmission at 60GHz with improved back-off efficiency. It achieves 5.7% power-added efficiency (PAE) at 5dB back-off with a total power consumption of only 90mW. Power gain and output 1dB compression point (P
_-1dB
) are 22dB and 10.2dBm respectively. A second Tx front-end, based on a class-A PA and Gilbert-cell upconversion mixer, is designed as a benchmark for comparison. With a similar value of P
_-1dB
, PAE of the class-AB prototype at 5dB back-off is three times higher and the total power consumption is 100mW lower than the benchmark Tx.