A 13 pJ/bit 900 MHz QPSK/16-QAM Band Shaped Transmitter Based on Injection Locking and Digital PA for Biomedical Applications Xiayun Liu, Student Member , IEEE,M e h r a n M . I z a d, Member , IEEE, Libin Y ao, Senior Member , IEEE,a n d

Abstract

This paper presents a 900 MHz highly digital trans- mitter capable of providing band shaped QPSK/16-QAM modula- tion for high data-rate applications with high energy ef ficiency. In- jection-locked ring oscillator is used for multi-phase carrier gener- ation which eliminates the use of power-hungry phase-locked loop. It also provides fast settling tim e that enables heavy duty cycling to maximize energy conservation. Direct modulation at power am- plifier is adopted to simplify the tran smitter architecture. Fabri- cated in 65 nm CMOS, the transmitter achieves maximum data rate of 50 Mbps/100 Mbps for QPSK/16-QAM with effective side- band suppression more than 38 dB . The chip occupies an active area of 0.08 mm and achieves a settling time of less than 88 ns. Under 0.77 V supply, it achieves an energy ef ficiency of 26 pJ/bit and 13 pJ/bit with and without band shaping respectively. The measured EVM is better than 6% for QPSK (at 50 Mbps) and 16-QAM (at 100 Mbps) while delivering 15 dBm of output power.