A theoretical investigation of the quarter-wavelength model-part 2: verification and extension

Abstract

The quarter-wavelength model states that the reflection of microwaves is minimized if the thickness of the film is mλ/4 where m is an odd integer and λ is the wavelength within the film . In part 1 of this work, published previously, it was shown that the theory behind this model is flawed and that it needs to be replaced using a wave superposition approach involving principles not beyond physics at college level. Through the verification of the results from formulae familiar to material scientists, it is shown here that many other concepts in current mainstream microwave absorption theory are used inappropriately including that reflection loss RL has been used to characterize microwave absorption from material instead of film and also that the results have been rationalized incorrectly by impedance matching theory. Impedance matching theory is developed from transmission-line theory for scattering parameter s 11 but cannot be applied to RL which is an innate property only for metal-backed film.