Jerusalem cross geometry magnetic substrate absorbers for low-frequency broadband applications

In this work, an ultra-thin microwave absorber with a Jerusalem cross (JC) resonator exhibiting a broad low-frequency absorption bandwidth was successfully designed and fabricated. The system is composed of a perfect electric conductor-magnetic-periodic metal three-layer structure. The top metal layer consists of a periodic JC, which can be used to obtain dual-bands and low-frequencies in L-band, S-band, and C-band applications. The simulations show that the magnetic absorber with a thickness of 2 mm exhibits two absorption peaks at 1.4  and 4.7 GHz, with a reflectivity of −10 and −8 dB, respectively. The L-band RL (reflection loss) of −4 dB bandwidth has 91% (1–1.91 GHz), whereas the S-band and the C-band of −4 dB bandwidth have 47% (2.87–5.68 GHz). The total thickness of the absorber measures only 1/100λ at 1.5 GHz. When a magnetic harmonic TM is polarized at an incidence angle of 75°, an average RL of −10 dB in the 1–8 GHz range is obtained. The equivalent L–C circuit and the power loss density clarify the mechanism behind the absorption. Such a low-frequency absorber can be used in various applications to quench microwave energy.