Fig. 2: Theoretical diagram and circuit model.
From: Electro-quasistatic and resonant cavity car body communication

a Inside excitation (bi-phasic/galvanic) measurements. b Outside excitation (capacitive return path) channel measurements, and c resonant cavity mode measurements in the Electro-quasistatic (EQS) regime. Depictions include local transmitter (TX) and receiver (RX) ground (GND) references.