Excitation of electromagnetic waves in a thin water layer using a coaxial probe

In this paper, two transitions between a coaxial line and a thin water layer are presented: one with symmetric structure and the other for a unidirectional wave propagation. In order to have a smooth transition and to achieve a wide bandwidth, an inverted glass cone is employed in the axially symmetric transition between a coaxial probe and a thin water layer. For the unidirectional design, a parabolic cavity made of a thin glass layer is added at one side of the water layer to reflect the electromagnetic waves to the desired direction. Simulation results show that omnidirectional and unidirectional propagation of electromagnetic waves can be successfully excited in the thin water layer through these two transitions respectively. The 10 dB bandwidths from 454 MHz to 914 MHz (67.3%) for the symmetric transition and from 463 MHz to 915 MHz (65.6%) for the unidirectional transition are obtained.