Half‐Wavelength Uncertainty Compensated Accurate Estimation of Dielectric Constant of Low‐Loss Dielectrics at GHz Frequencies

The presented paper addresses the divergence issue of Nicholson–Ross–Weir (NRW) algorithm encountered during the electrical characterisation of half‐wavelength or thicker low‐loss dielectric materials. To overcome this limitation, an S 21 ‐parameter‐based extraction method is proposed for determining the complex permittivity of low‐loss dielectrics in rectangular waveguide and free‐space measurement environments at GHz frequencies. The iterative Newton method, supported by an initial guess, is employed for permittivity extraction. Explicitly formulated equations suitable for broadband iterative computations are presented. Measurements on a variety of low‐loss dielectric material specimens in both rectangular waveguide and free‐space measurement environments in X‐band are demonstrated to ascertain the accuracy and stability of extraction procedure. Root‐Mean‐Square‐Error (RMSE) calculations across the frequency band, along with comparisons to other reported extraction techniques are presented to demonstrate accuracy improvements. Furthermore, the uncertainties associated with the extracted complex permittivity in different measurement environments are analysed and discussed.