A Re-evaluation of the mechanism of microwave absorption in film – Part 1: Energy conservation

Abstract

Energy conservation for a film with or without metal-back, or an interface provides the theoretical basis for understanding the mechanism of microwave absorption by the film. Film and material have been confused in the past and reflection loss defined for film has been used to characterize material. Such practices have lasted for many years, which has caused many problems in microwave absorption material research. Microwave absorption for film can be defined by considering energy conservation, which provides irrefutable evidence that film and material are different. Some difficult issues, such as that for an interface the voltage of the transmitted beam may be larger than that of the incident beam, and that for a film with a certain thickness, the voltage of the beam reflected from the interface with metal-back can exceed that of the incident beam, have been successfully explained. It is proved using complex variable functions that energy conservation concepts are different for film and interface related to material that absorbs microwaves. For films that absorb microwaves, it is shown that the absolute value of the reflected energy from an interface represented by RM2 can be greater than 1 and the real part of RM2 can be negative, especially at resonance.