In this letter, the design of a lightweight magnetic radar absorber (RA) having broadband bandwidth in frequency range of 1-18 GHz is demonstrated. A 5-mm-thick magnetic RA with weak wave-absorbing performance is obtained on the basis of polyurethane foam filled with flake ferrous microwave absorbent. The use of frequency selective surfaces (FSSs) results in a significant increase of the absorbing intensity and operating bandwidth of the RA. By selecting the unit dimensions and modulating the location and square resistance of FSS, a maximal operating bandwidth with the reflectivity below -10 dB can be obtained. Experimental results are presented and compared to numerical simulations, and they demonstrated that the RA embedded with lossy FSS has a super broad bandwidth of 3.19-18 GHz with the reflectivity below - 10 dB for the double-layer case. The density of the absorber is only 0.62 g/cm3, which is far more less than that of the conventional magnetic coating radar absorbing materials (RAMs).
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Cheng et al. (2012) studied this question.