Permittivity

A novel low-loss planar dielectric waveguide is proposed. It is based on a high-permittivity dielectric slab parallel to a metal ground. The guiding channel is limited at the sides by a number of air holes which are lowering the effective permittivity. A mode with the electric field primarily parallel to the ground plane is used, similar to the E11x mode of an insulated image guide. A rather thick gap layer between the ground and the high-permittivity slab makes this mode to show the highest effective permittivity. The paper discusses the mode dispersion behaviour and presents measured characteristics of a power divider circuit operating at a frequency of about 8 GHz. Low leakage of about 14% is observed at the discontinuities forming the power divider. Using a compact dipole antenna structure, excitation efficiency of more than 90% is obtained.

The knowledge of soil electric properties is very important, specially for electromagnetic wave propagation at low and medium frequency (LF and MF). This knowledge allows to compute the wave attenuation in order to know the transmitting power to cover a specific service area. In this paper dielectric constant, loss factor, loss tangent, and conductivity for different soils: dry sand, humid

MEMS, Electromagnetic field is a way to manipulate droplets, beads or cells without direct contact. In particular, dielectrophoresis is often used in BioMEMS applications, for cell handling operations such as moving, sorting, trapping or deforming cells. In this paper, a 3D focusing geometry for the electrical field is proposed, that permit the trapping of single cell, or cells pair, thanks to positive dielectrophoresis. The design is explained with highlighting the focusing effect versus insulator shape for trapping cells. A prototype based on classical MEMS process and results of first trapping are presented.

To detect partial discharges (PD) in equipment such as gas insulated substations and power transformers, UHF couplers can often be fitted at dielectric apertures (windows) in the metal cladding. Waveguide theory is used to show how the window structure affects PD detection sensitivity in the UHF band. By increasing the relative permittivity of the propagation medium, the effective diameter of the window can be increased, leading to improved UHF signal transfer. A given sensitivity to PD can therefore be achieved using a smaller, more robust window, which is particularly important when the insulation is a liquid or gas under pressure. Alternatively, if the window size is fixed, filling it entirely with a dielectric material can improve PD detection sensitivity. A window designed specifically for coupling UHF signals is proposed as an alternative to the use of internal couplers.