Multi-Band Polarization-Insensitive Metamaterial Absorber for Microwave Based on Slotted Structure and Magnetic Rubber

A design method of five-band polarization-insensitive metamaterial absorber (MMA) based on the slotted structures and the magnetic rubber is proposed for L-, S-, C-, X-, and Ku-band applications. The slotted structures of the top layer, which evolved from two square rings, are used to excite multi-resonance. The range of the electromagnetic (EM) parameters of a magnetic rubber substrate, which is used to adjust the equivalent impedance of the absorber to match the free space impedance in different bands, is estimated using the impedance matching principle. A series of magnetic rubber substrates based on the estimated EM parameters are prepared and measured, whose thickness is only 0.7 mm, meeting the thin design requirements. The absorption of the proposed absorber greater than 90% at 1.7 GHz, 3.87 GHz, 5.96 GHz, 9.4–10.4 GHz, and 14 GHz is achieved when the doping amount of the carbonyl iron powders is 200%. The absorbing performance of the absorber with measured EM parameter agrees well with the theoretical estimates, which validates the accuracy of the proposed design method.