Measurements of Electromagnetic Radiation Propagation through Biomaterial Samples Based on Harvest Residues

The aim of this research was to determine the efficiency of electromagnetic (EM) radiation absorbers based on biomaterials from harvest residues (soybean straw, wheat straw, and clover straw) for the additional protection and/or construction of residential buildings. To determine their protective properties, the transmission parameter S21 was measured through harvest residues in the frequency range from 300 MHz to 5 GHz. Important parameters of the tested samples included sample type, sample thickness, and humidity. The measurement results showed that the transmission parameters decreased with an increase in the sample thickness, moisture, and frequency. Regarding this type of substrate, soybean straw showed the lowest values of parameter S21 for all measurements except for the case of the highest amount of moisture (34.48%), for which clover straw showed the lowest value of the transmission parameter. The greatest reduction in the S21 transmission parameter was 43.80 dB for a soybean sample of 300 mm thickness at a frequency of 4.93 GHz. These tests were performed on samples that were not additionally structured (additives, pressing, additional shredding, etc.), so it was possible to optimize their structure and conduct further research.