Optimal Size of Uniform Aperture for Near-field Penetration through Lossy Medium

We present our investigations on the optimal size of uniform antenna aperture for the maximum near-field penetration of microwave signals through lossy materials. Penetration ability of an antenna through a certain depth in a lossy material depends on how much the radiated power from the antenna is focused at that depth. A figure of merit, the near-field 3 dB beam radius, is used to define this focusing. Empirical formula to calculate the minimum 3 dB radius and its location are provided in the article. Verification of the results has been carried out by simulations using a commercial electromagnetic solver