Transceiver for Ultrasonic Intra-Body Area Networks With Non-Coherent BPSK Detection

This brief presents a transceiver for an Ultrasonic Intra-Body Area Network (UIBAN) enabling regular monitoring of low data rate bio-signals. The modulation scheme is Binary Phase Shift-Keying (BPSK) because of its superior energy efficiency compared to the other binary modulations. Therefore, a BPSK detector composed of a single D flip-flop is proposed. The carrier frequency is 1 MHz and the bit rate is 7.8125 kbits/s . The integrated circuit (IC) was designed in the 0.35 \mu \text{m} CMOS technology from AMS. The complete transceiver was measured with 2 2mm diameter ultrasound transducers. The measured Bit Error Rate (BER) was 1.8\times 10^{-3} and 1.3\times 10^{-2} over a distance of 3.1 cm and 17.5 cm in castor oil, although subjected to many reflections. This is, to the authors' knowledge, the highest measured communication distance with two ultrasonic transducers of a volume lower than 10 mm^{3} in an environment similar to that of the human body.