A Low Power Pulse Position Modulation Based Ultra-wideband Transmitter for Implantable Sensors

This paper demonstrates a novel scheme for converting analog biomedical signal to a M-ary PPM (Pulse Position Modulation) modulated signal to be transmitted using UWB (ultra-wideband) wireless link. PPM modulation provides higher data rate than on-off keying (OOK) or pulse amplitude modulation (PAM) as more than one bit can be represented per symbol. The proposed scheme eliminates the use of power hungry ADC (analog-to-digital converter) blocks that are used in conventional biosensor read-out circuitry. This scheme also enables the option to modify the sampling rate of the acquired signal without changing the power consumption of the overall system. Implemented using a standard 180nm CMOS process, the readout circuitry along with the UWB transmitter consume only 47 mu A current with 1.8V supply voltage.