Measurement of frequency-dependent equivalent width of substrate integrated waveguide

In this paper, a method is developed to measure the frequency-dependent equivalent width (FDEW) of the substrate integrated waveguide (SIW). Based on the deembedding concept, the formulas of the measurement procedures are derived, and then the measured equivalent width corresponding to each frequency is applied to the transmission/reflection method to acquire the substrate dielectric constant. The measurement method is experimentally verified over the frequency range from 26 to 40 GHz. The measured FDEW of the SIW is compared with that calculated by the empirical equation. Furthermore, the results of the measured dielectric constant are shown to be in reasonable agreement with those measured by the ring resonator method. It demonstrates that the developed method is an effective measurement approach to characterizing the SIW.