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With vitamin A acetate as raw material, ethylenediamine retinyl Schiff base salts coordinated with rare earth ion La3+, Ce3+ were synthesized, and the structure of the products was characterized by FT-IR and Raman spectra. The electromagnetic parameters in the frequency range of 2-18 GHz were measured by microwave vector network analyzer, its reflectivity was calculated, and the main factors and mechanism that affect the wave-absorbing performance of rare retinyl Schiff base salts were discussed. The results show that the coordination bond is formed by the rare earth ions and Schiff base. The reflectivity of Schiff base coordinated with La3+ ion is –16 dB at 12.9 GHz (bandwidth with reflectivity better than –10 dB is 3.1 GHz), the reflectivity of Schiff base coordinated with Ce3+ ion is –18.8 dB at 12.7 GHz (bandwidth with reflectivity better than –10 dB is 3.4 GHz). Microwave absorption performances of the both are superior to the wave-absorbing performance of Schiff base coordinated with non-rare earth ions.

A chaos patterned metasurface absorber (CPMA) with three strong absorption peaks and a wide bandwidth has been designed. This CPMA presents a single-layer sandwich structure, which not only enables easy optimization by adjusting the surface pattern and model size but also contributes to the continuous effective bandwidth (EBW, with an absorptivity larger than 90%) from the multiple adjacent absorption peaks. The continuous EBW is from 4.28 to 9.56 GHz with a bandwidth of 76.3%. Meanwhile, analyses on the distributions of the surface current, electric field, and power loss density illustrate that the absorption mechanisms are mainly magnetic coupling resonance and dielectric loss. The experimental results confirm the good absorption performance with multi-peak and wide bandwidth for the fabricated CPMA sample, which shows potential applications in the field of anti-electromagnetic interference. [ABSTRACT FROM AUTHOR]

The complementary-modeled Rossler chaotic metamaterial (CRCM) with FR-4 dielectric layer is proposed to design metamaterial absorber with multi-resonance peaks. Under "master-slave" boundary condition in high-frequency structure simulator (HFSS) software, the electric field between adjacent boundaries presents phase difference which can simulate an infinite array. The research results show that the CRCM demonstrates multi-resonant peaks from 4 GHz to 10 GHz, and the area of metal patterned-layer can obviously regulate the resonant peaks. The CRCM presents a linear polarization conversion peak around 5.80 GHz, its polarization conversion ratio (PCR) is near 100%. The PCR is also larger than 80% from 5.56 GHz to 5.95 GHz. Through the surface current density distribution and the comparison between the CRCM and complementary-modeled double ring metamaterial (CDRM), the main factors generating polarization conversion are the asymmetry of metal pattern layer and magnetic resonance caused by reverse current. The CRCM also has two strong absorption peaks located at 6.31 and 9.37 GHz, respectively. Dielectric loss and ohmic loss are the main microwave loss mechanisms proved by volume and surface power loss density distribution. The resonant frequencies derived from L – C resonant circuit are well consistent with the simulation data and measurement results. [ABSTRACT FROM AUTHOR]