Propagation of Electromagnetic Waves Excited by a Capacitive Coupler in a Cylindrical Water

The electric near field generated by a capacitive coupler rapidly decays in air, but if a dielectric is placed within the range where the near field spreads, some electromagnetic waves are excited in and on the dielectric material. The wave propagates through the dielectric as a transmission line and carry electric power. It is found that common materials such as water can be used as a cable to deliver microwave. In this study, a longitudinal electric field generated from a coupler resonating at 2.45 GHz was injected into a column of fresh water to investigate the propagation characteristics of electromagnetic waves propagating through water by simulations. Water has high permittivity and can be a low-loss transmission line in GHz band. A cylinder of water 16 mm in diameter and 1 m long could transmit power at 2.45 GHz with a path loss of −4.2 dB.