A Wideband Absorbing Structure Based on Two Different Resistance Layers and a Magnetic Layer

In order to design wideband absorption, especially at the low-frequency band, a magnetic layer was used in the absorbing structure based on two different resistance layers. The two resistance layers were a Jerusalem cross and a ring shape made of conductive carbon black, while the magnetic layer was filled with FeSi and silicone rubber, with polymethylacrylamide and a low dielectric epoxy plate as the medium layer. The simulation results show that the absorption bandwidth below -10 dB is 3.1-18 GHz (bandwidth ratio 141.2%), the total thickness is 7.2 mm, the absorption peak appears at 4.3 GHz, and the reflection loss (RL) is lower than -40 dB. The wave-absorbing characteristics were analyzed using the equivalent circuit model, which indicated the absorbing structure maintained a good impedance match with the free space. The effects of parameters including the impedance layer resistance, magnetic coating thickness and dielectric layer thickness on the absorbing performance were analyzed. Increasing the resistance of the first impedance layer makes the absorption peak decrease, increasing the magnetic coating thickness makes the absorption peak move to the low frequency, and increasing the dielectric layer thickness makes the absorption peak increase first and then decrease. The experimental results show that the absorptive structure has an absorptive performance below -10 dB in 3.45-18 GHz, indicating that the absorber has good potential application in the field of microwave absorption.