A nondestructive method for measuring the complex permittivity of dielectric materials at microwave frequencies using an open transmission line resonator

Abstract

A new nondestructive method of measuring the dielectric constant and loss tangent of dielectric materials using an open transmission line resonator is developed. The method is based on perturbing the fringing Held at the open end of the transmission line by an unknown dielectric material, and is applicable not only for solid dielectric materials but also for liquids and gases. Forming or shaping of solid dielectrics is not required, but there should be a small flat area available for contact. Thickness of the dielectric material terminating the line does not affect the measurement unless the material is thinner than twice the spacing between conductors of the coaxial line. The experimental results obtained for some solid dielectric materials, liquids, and biological tissue show that the method has sufficient accuracy for most applications up to about

A Nondestructive Technique for Local Measurement of Dielectric Loss in Substrates of Integrated Circuits at Microwaves

“…2 indirectly show the effect, which was observed in [1,2], of emission of electromagnetic waves from the coaxial resonator's hole as a function of substrate thickness and permittivity. The emission from the coaxial resonator can be detected on the outside of the resonator with an antenna connected to a receiver (e.g., to a spectrum analyzer) or with an energy-flux-density measuring device at a sufficiently high oscillation power in the resonator.…”

“…A resonator designed as a segment of an open-end coaxial line with a measurement hole in the form of a circular slot was proposed in the 1970s [1] for nondestructive local measurements of relative permittivity ε ' and loss tangent tan δ of materials in the microwave range. The plate of a dielectric material being measured is applied to the resonator's measurement hole and, by use of the obtained analytical relationships, parameters ε ' and tan δ in a local region of interaction of the resonator edge field with the dielectric are calculated from the change in the resonator's resonance frequency.…”

Prospective Applications of Microwaves in Medicine

“…This method can be considered as very accurate. Moreover, we can achieve a good repetition of the results when we maintain the phase stability of the measuring coaxial cable (Tanaba & Joines, 1976). In this work, this application was selected for the main method for measuring complex permittivity of biological tissues because of its non-invasive nature.…”

Prospective Applications of Microwaves in Medicine

“…It is a well-known method for determining the dielectric parameters (Tanaba & Joines, 1976). This method is based on the fact that the reflection coefficient of an open-ended coaxial line depends on the dielectric parameters of material under test which is attached to it.…”