Highly efficient microwave absorber surface design for energy harvesting in 5G frequency band

5G communication systems represent a significant advancement, particularly in meeting the requirements of fast data traffic and low latency, and the global transition to this technology is progressing rapidly. The high-frequency microwave energy emissions of 5G communication systems have increased interest in energy harvesting efforts in these frequency bands to partially meet the growing energy demand. This study aims to approach the usability and cost of high-efficiency microwave absorber structure design for energy harvesting in 5G frequencies to the optimum level. A unit cell design capable of high-efficiency absorption in the targeted frequency range was performed in four different stages. The design and simulations were conducted using the CST STUDIO program. The results obtained for each stage of the design were analyzed, and additional analyses were carried out for substructure material and thickness based on the optimal performance of the unit cell structure in terms of absorption. An absorption of 98.04% at 3.8 GHz was achieved with a unit cell absorber structure designed on an FR4 material with a thickness of 1.5 mm. Subsequently, this designed unit cell was separately designed and simulated with different periodic arrays to transform into an absorber surface structure. As a result, high absorption rates of 98.94% and 98.35% were obtained at operating frequencies of 3.8 GHz and 4.2 GHz, respectively, with a 2x2 array of the designed microwave absorber surface structure. It was observed that the structure provided absorption of over 85% within a 1 GHz bandwidth between 3.5 GHz and 4.5 GHz. To verify the simulation results, a prototype of the absorber surface was produced, and measurements were performed in a laboratory environment. Significant consistency was observed between the data obtained from these measurements and the simulation results. All these data indicate that the proposed absorber surface is a suitable candidate for energy harvesting in the n77 and n78 bands of 5G.