Figure 1. Five types of intrabody communication.

(A) Signal is transmitted from a Tx to a Rx, both located on the skin, with the body capacitively coupled to the Tx and Rx electrodes. The Tx and Rx are also capacitively coupled to the ground, but capacitance between the body and ground reduces the efficiency of signal transmission. (B) Signal is transmitted from a Tx implanted in the tissue to a Rx on the skin. The Tx and Rx electrodes are galvanically coupled to the tissue. Most of the current passes between the two Tx electrodes, but sufficient signal transmits across the tissue to be detected by the Rx. (C) Using x-antennas to shape the current path, creating a higher impedance path between the Tx electrodes, stronger signal is detected at the Rx than without x-antennas. (D) Signals are detected by an implanted Rx, which reduces signal attenuation and power demands compared with skin-mounted Rx electrodes. (E) By using only one Tx electrode and one Rx electrode galvanically coupled to the tissue, the path between Tx electrodes has higher impedance than the path to the Rx, resulting in less signal attenuation. High-frequency, charge-balanced, alternating-current signals prevent charge build up.

Rx: Receiver Tx: Transmitter.