For miniaturization of wearable devices, battery-life extension and even battery-free operation are increasingly demanded. Intra-body-power-transfer (IBPT) has emerged as an alternative solution to energy harvesting  and wireless power transfer  because it can supply power regardless of the locations of the power source and the wearables on the body  -. However, the channel characteristics of the body are prone to vary with environmental changes, making it hard to transfer sufficient power consistently . To address this issue, a system with frequency and power adaptation for node-specific power delivery optimization was proposed . However, it requires RX-to-TX backward data communication, disrupting the power transfer during the communication. Alternatively, a maximum-resonant-power-tracking (MRPT) was proposed. It adaptively changes the carrier frequency (fcarrier) so that the TX output voltage (VTX) is maximized . However, its tuning phase, which is required for every MRPT operation period repeatedly, makes the IBPT discontinuous and inefficient.