Surface-Mounted Parallel-Plate Coupler for Cylindric Dielectric Waveguides

Abstract

Surface-mounted parallel-plate capacitors (PPCs) can be used as transducing elements in wireless communication, for example in human body-dedicated applications, such as healthcare monitoring or activity tracking, which require robust wireless communications and user-convenient implementation. In this context, PPCs are an attractive element due to their mobility, noninvasive positioning, and small form factors. Moreover, they are relatively easy to analyze with a simple design. This work studies the use of PPCs on dielectric, cylindrical waveguides as a precursor to the relatively complex electromagnetic environment that the human body is. The electromagnetic fields surrounding PPCs placed on a dielectric medium are described theoretically. This theory involves a combination of surface waves, inductive coupling, and quasi-static coupling between PPCs. In dielectric (cylindric) waveguides, the material's dimensions, and frequency of excitation dictate whether propagation of certain modes can occur. This manuscript shows, on the one hand, that these modes can be excited by a surface-mounted waveguide coupler such as PPCs, and on the other hand, that the associated propagation is governed by modal characteristics.

A Simulation Study of Capacitive Body-Coupled Communication along Human Limbs

“…5 shows that for 𝑑 > 3𝑐𝑚, the cylindrical model is an excellent predictor of the propagation along the arm of the anatomical model. The results presented here are in line with previous results, where we showed that PPCs can be used to excite propagating modes along dielectric cylinders [5] and that they can be used for BCC communication around 450 MHz [3].…”

“…The trend in propagation along a real human arm can be predicted accurately using a cylindrical model. Since propagation along a cylindrical, lossy waveguide can be described analytically [1,5], this opens up the possibility of a theoretical analysis of this frequency dependent propagation. Using modal analysis of the cylindrical model, we aim to show that also in this configuration this effect is due to surface waves which are tied to propagating modes along the arm.…”

“…1 on a cylinder's mantle with radius r (𝐸 (𝑓, 𝑑, 𝑟)) were extracted. We have shown previously that this quantity can be used as a good proxy for RF-EMF communication using PPCs on dielectric cylinders [5] and using C-BCC [3]. After each simulation using the VFM, the electric fields (𝐸 (𝑓, 𝑑)) were extracted along the surface of the phantom's arm along a line that is the intersection between the plane parallel to the YZ plane containing the voltage source of the PPC and the boundary of the phantom, as illustrated in Fig.…”