Phenomenon of Microwave Reflection Reduction for Liquid Foams at Initial Stage of Their Existence

Coating metal surfaces with liquid foams is a promising approach to reducing microwave reflectivity. Due to disintegration processes, liquid foams quickly change their properties over time. The objective of this study is to experimentally evaluate changes in the masking properties of liquid foam with time. The measurements were carried out in the frequency range of 38–52 GHz using original measuring equipment that implements the principle of Fourier holography in the frequency-time domain. Measurements are carried out in less than 1 second with median averaging and synthesizing time pulses with a duration of 70 ps at 3 dB of the envelope. It is shown that for the observation period from 0 to 15 minutes, the reflection coefficient in the range of millimeter waves decreases from 0.008 to 0.001, remaining at a level sufficient for masking problem solution. The novelty of the results is the study of the initial stage of the existence of liquid foam during the first 25 minutes.