Location Dependence of WPT Efficiency Characteristics Between a Circuit-Shaped Leaky-Waveguide and a $\lambda / 2$ Dipole Antenna Due to Electric Field Distribution

WPT efficiencies between a circuit-shaped leaky-waveguide and a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\lambda / 2$</tex> dipole antenna set at locations <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$A^{\prime}, B^{\prime}, C^{\prime}$</tex> and D' were firstly calculated from the scattering parameters obtained by the FDTD method. The antenna height from the top surface of the waveguide was parameterized as 15,30 and 60 mm. The <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$30-\text{mm}$</tex> height cases exhibited the highest efficiencies, while those of 60 mm height did the lowest. Sixty-mm height cases had more transmission attenuation than <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$15-\text{mm}$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$30-\text{mm}$</tex> cases, which should result in a decrease in WPT efficiency. The height of 30 mm was actually a quarter of a wavelength, which gave better transmission between the dipole antenna and the waveguide. Looking at scattering parameters, the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$S_{11}$</tex> 's show periodic characteristics with respect to the frequency axis for all simulated locations. <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$S_{21}$</tex> 's were found to be maximum at 2.45 GHz for locations <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$A^{\prime}, B^{\prime}$</tex>, and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$D^{\prime}$</tex>, while to decrease at 2.45 GHz at location C'. Because the dipole antenna was set parallel to the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$y$</tex>-axis direction, the electric fields in the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$y$</tex>-axis at location <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$A^{\prime}, B^{\prime}, C^{\prime}$</tex> and D' in <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$y$</tex>-axis were compared. Its magnitude at location <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$C^{\prime}$</tex> was the smallest value, which should affect the characteristics of scattering parameter and WPT efficiency.