LAUSR

This work presents the design and implementation of an ultra-broadband quadrature common-mode amplitude modulator (QCAM) to generate high power back-off efficiency 16-QAM signals. The proposed QCAM transmitter consists of I- and Q-path PAM4 modulators, which digitally modulate the power amplifier (PA) output stage to relax the linearity requirement. An interleaved differential transformer-based coupler is proposed for wide-band combination of the baseband and LO signals. The I and Q PAM4 signals are combined using an on-chip Wilkinson power combiner to generate the 16-QAM output signal. The 28-GHz 16-QAM transmitter test chip, implemented in 65-nm CMOS, achieved measurement results of 11.35 dBm average RF output power, 9.2% DC-RF efficiency, 16 Gb/s data rate, and −24 dB EVM.