A Transparent and Flexible Absorber for Electromagnetic Interference Suppression, Designed for 5G Communication and Sub-6G Applications

As 5G technology rapidly advances, the extension of spectrum into millimeter-wave bands enables higher data speeds and reduced latency. However, this frequency expansion introduces significant electromagnetic interference (EMI) issues, particularly in environments with dense equipment and base stations. To tackle these challenges, this paper presents a multilayer transparent ultra-wideband microwave absorber (MA) using indium tin oxide (ITO) that operates between 4 and 26 GHz. This optimized MA design successfully achieves absorption from 4.07 to 25.07 GHz, encompassing both the 5G Sub-6 GHz and n258 bands, with a relative bandwidth of 144% and a minimal thickness of 0.129λL (where λL is the free-space wavelength at the lowest cutoff frequency). For TE and TM polarization with incidence angles ranging from 0° to 45°, the MA demonstrates exceptional performance, maintaining a relative bandwidth exceeding 120%. Notably, for TM polarization with incidence angles between 60° and 70°, the MA can sustain an absorption capacity with a relative bandwidth greater than 100%. By integrating the principles of impedance matching, surface current theory, and equivalent circuit simulation fitting, the absorption mechanism is further analyzed, thereby confirming the reliability of the design. This design offers exceptional wideband absorption, optical transparency, and wide-angle incidence characteristics, demonstrating great potential for applications in electromagnetic stealth, EMI suppression, and electromagnetic compatibility (EMC) in 5G communications.