An open resonant system for permittivity measurements in the millimeter wave range

In the present work, we will discuss the scope for permittivity measurements of cylindrical-shape samples by means of the given open resonator (OR). For this purpose, cylindrical-shape TE_οiα-mode cavities are normally used in the centimeter wave region. But with reduction in the wavelength, the geometric size of the cylindrical cavity should be decreased in order to keep its single mode operation. So, the millimeter and, further, submillimeter wave cylindrical cavities become so small in geometric size that it is not practical to use them. At those wavelengths, the OR we suggest lends itself well because the diameter of the circular waveguide, an element of the OR design, measures several wavelengths. In addition, the absolute permittivity measurements are most favorable because they need not a preliminary calibration of the OR resonance frequency related to the permittivity of samples with known characteristics.