Absorbing material_ Absorbing frequency band absorbing material must have the four characteristics of material (coating): small thickness (thin), low density (light), large absorption band (wide), and high absorption strength (strong). How to broaden the absorption The absorption frequency band of wave materials is the focus of current wave absorbing materials. Commonly used electromagnetic wave frequency bands are widely used from meter wave (~MHz) to millimeter wave (~GHz) to terahertz electromagnetic wave (~THz).
At present, advanced communication technology represented by 5G communication technology has expanded the communication frequency band from 700 MHz to 6 GHz and even millimeter waves. On the one hand, the increase in operating frequency has compressed the communication base station to the size of a suitcase, and the interference between electromagnetic signals has increased; on the other hand, signal receiving ends such as mobile phones need to add new antennas, which further reduces the design space of the receiving end. The interference between signals is further enhanced. The emergence of these practical applications not only requires the absorbing material to be thinner, but also requires the absorbing material to have a wider absorption frequency band. In order to make a kind of absorbing material meet the demand of electromagnetic wave absorption in multiple frequency bands as much as possible, broadband absorbing materials have become the first choice. However, this is not an easy task.