Dielectric Constant Estimation Using Calibration-Free Reflected Voltage Measurements

In this paper, a waveguide-based dielectric sensing technique for the measurement of the relative permittivity of planar low-loss materials is presented. The material under test (MUT), assumed to be thicker than one half of wavelength (λg/2), is sandwiched between the waveguide’s aperture and a matched load. The reflected voltage magnitude is measured at the waveguide’s input port by relying on a custom-built reflectometer. The measured reflected voltage values are then used to calculate the dielectric constant of the MUT over the waveguide’s operating frequency range. The proposed method offers a major advantage of not requiring pre-calibration. This technique is tested on multiple material samples where accurate estimates of their respective dielectric constant values are obtained.