Analysis of Mutual Coupling Using the Asymptotic Friis Formula

The accurate prediction of power transmission between two antennas is important for numerous applications, including wireless power transfer and communication link analysis.The classical Friis transmission equation, while reliable in the far-field regime, exhibits reduced accuracy in the near-field regime.In this study, the gain reduction factor including four asymptotic terms have been presented to increase an accuracy in the near-field regime.Utilizing the asymptotic Friis formula with the gain reduction factor for circular apertures, an improved accuracy of the power transmission in a very close near-field regime is obtained.It is demonstrated that the formula is advantageous in terms of predictive accuracy at close distances.