Tijana Dimitrijevic

This paper investigates the impact of the human body on impedance matching of wearable microstrip antennas under bending conditions. A cylindrical 3-D Transmission Line Matrix (TLM) in-house solver with conformal mesh is used for parametric analysis, enabling accurate modeling of curved geometries and antenna–body interaction. The study focuses on separating body-induced effects on reflection coefficient and resonant frequency from bending deformation and related mechanisms such as patch elongation and substrate permittivity variation. Results show that body loading significantly degrades impedance matching, while bending can partially reduce this effect by decreasing electromagnetic coupling with tissue. The proposed approach provides an efficient and physically consistent framework for predicting antenna performance in realistic wearable environments.

This paper investigates the potential of the Transmission Line Matrix (TLM) method and highlights the efficiency of a conformal cylindrical mesh for analyzing the tunable capabilities of a wearable slotted antenna under bending conditions. Various configurations of polygon-shaped and U-shaped slots inserted into the radiating patch of a rectangular antenna are considered to illustrate their tuning effects on antenna parameters. The cylindrical TLM approach is demonstrated to be particularly effective for the efficient and accurate analysis of a flexible slotted antenna attached to the human body, focusing on resonant frequencies and reflection coefficients under different bending angles. The simulated results confirm the consistency of frequency shifts caused by bending, while the cylindrical mesh provides precise analysis of the impact of slot shape and size on antenna performance.

This paper demonstrates how the cylindrical TLM method can be used to investigate the effectiveness of the enclosure shielding. For that purpose, two empty, metallic, cylindrical enclosures with embedded monopole antenna inside, and a small aperture cut out at two different locations on the cavity side wall are considered. An electromagnetic field distribution is investigated outside the enclosure and the shielding effectiveness is determined.

This article demonstrates a development and verification of the wire junction network model implemented into the transmission-line modeling solver based on the cylindrical grid to allow for modeling of complex wire structures. This new added feature will allow this solver to be used for larger number of applications while providing the most reliable and efficient results considering that for specific geometrical structures, such as those of circular/cylindrical shape, the usage of the cylindrical mesh is the most adequate one as it perfectly aligns to these structures. The given approach is proved on a simple cylindrical cavity resonator with embedded monopole and loop antennas where the wire junction model is used to create the loop antenna. Presented results have shown better efficiency of the cylindrical mesh over the cubic one and a very good agreement with the measured results.

The impact of deformations on wearable antenna performance has been analyzed both experimentally and computationally. However, the reported results have been inconsistent and often contradictory. This paper highlights how the choice of computational mesh, namely cubic and curvilinear cylindrical mesh, that are applied to the problem of cylindrically bent antenna can affect the results and subsequent conclusions. By deploying both meshes within the same time-domain numerical algorithm means that the differences in results can only be attributable to the discretization method used. Finally, a cylindrical mesh is used to further characterize the impact of bending on antenna resonant frequency, bandwidth and radiation pattern. Bending in both E- and H- plane is considered.

This paper presents the suitability and computational features of the cylindrical TLM approach, when it is used as an accurate and efficient alternative for the analysis of the bending effect on performances of the antenna operating in an on-body mode. A design goal was to create the model of the rectangular patch antenna wrapped around the part of a cylinder, which can be used to represent a human body (torso, leg, or arm) and simultaneously to model dielectric properties of muscle tissue. Moreover, the paper illustrates problems in terms of accuracy and limitations when the antenna deformation is modelled by using numerical methods based on the cubic mesh. The advantages of the cylindrical TLM method over the rectangular TLM approach have been emphasized through an analysis of how the bending affects the resonant frequency of the antenna.

Accurate near-field measurements for either deterministic or stochastic electromagnetic fields characterization require a relevant process that removes the influence of the probes, transmission lines, and measurement circuits. The main part of the experimental work presented here is related to a calibration procedure of a test setup consisting of a microstrip test structure and a scanning loop probe. The calibration characteristic, obtained by comparing measured and simulated results, is then used to convert the measured voltage into the magnetic field across and along the microstrip line at the specific height above it. By performing the measurements and simulations of the same test structure with the loop probe in the presence of an additional scanning probe, the influence of the additional probe to the measured output is thoroughly investigated and relevant corrections are given. These corrections can be important when two-point correlation measurement is required, especially in scanning points when two probes are mutually close.