A small-footprint Body Channal Communication transceiver using only one Phase-Locked Loop as modulator and demodulator

Wearable devices require very tiny size, and this demands chip area as small as possible. In this paper we propose an ultra-compact transceiver for Body Channel Communication (BCC). The main block of the transceiver is only one phase-locked loop (PLL) circuit which achieves both Frequency-Shift Key (FSK) modulation and demodulation of the system. This ultra-compact structure thus largely simplifies the transceiver circuit, and saves most of the core area. In addition, to improve the frequency accuracy of the FSK transmission, an adaptive frequency calibration (AFC) circuit is proposed, working together with fully-differential small footprint ring-based voltage controlled oscillator (VCO). The proposed PLL-reused transceiver works well at a data rate of 200k bps, and occupies a core area of only 0.273 mm 2 in 0.13um CMOS process, which is even smaller than some 65nm CMOS transceiver circuits.