A 400MHz/900MHz Dual-Band Ultra-Low-Power Digital Transmitter for Biomedical Applications

This paper presents a 400MHz/900MHz dual-band ultra-low-power digital transmitter with high energy efficiency for biomedical applications. Direct modulation at local oscillator and digital power amplifier is adopted to simply the transmitter architecture. With edge combining, the dual band transmitter shares a single digital controlled ring oscillator. The 400MHz transmitter adopts 16QAM modulation scheme with the ring oscillator under injection-locked while the 900MHz transmitter adopts BFSK with open loop ring oscillator. Fabricated in 65nm CMOS, the chip occupies an area of 1.3mm
²
. Under 0.5V supply voltage, both band transmitters consume less than 0.6mW power while delivering -15dBm of output power and the 400MHz transmitter achieves an energy efficiency of 53pJ/bit. The measured EVM is 4.35% for 16QAM at 10Mbps and the FSK error is 5.08% at 2Mbps.