Low power CMOS transmitter for biomedical sensing devices

We describe in this paper two low power transmitters that operates within the 402-405 MHz band allocated for medical implant communication systems (MICS). A frequency modulation scheme is employed. Each one of the transmitters includes a frequency synthesizer, a power amplifier and a matching network. The difference between the two architectures relies on the frequency synthesizer, which uses a new oscillator topology. These circuits are based on the Pierce configuration and use a surface acoustic wave (SAW) resonator. Both versions have been implemented in a 0.1 Hum CMOS process from TSMC and their performances have been compared. With a total power consumption of 2 mW, the radiated power is 0.3 mW allowing a transmission range of about 5 meters.