Research On Transmission Characteristics Of The Artificial Electromagnetic Absorptive Structures

Both electromagnetic communication and absorption performances can be of crucial importance in the stealth military field.Artificial electromagnet ic absorptive structures are widely employed as spatial reflection reduction applicatio ns due to their attractive absorption characteristics.However,the communication performance of antennas may be influenced by covering typical absorptive structures.Th erefore,it is important to study the transmission characteristics of artificial electromagnetic absorptive structures.The transmissive artificial electromagnetic absorptive structure is a kind of plane periodical structure that can provide transmission and absorption behaviors.Nevertheless,the absorption and transmission performances within the operating band may affect each other,which brings challenges to this type of design.For the published designs in literature,the performances of the transmissive artificial electromagnetic absorptive structure are limited by their design methods.Many of these works are difficult to realize a pass-band within the high frequency,meanwhile,their absorption bands are separated and insertion loss within the transmission band is relatively high.To overcome these drawbacks,this subject focuses on th e research on the transmission characteristics of the artificial electromagnetic absorptive structures.The main contents of this paper can be summarized as follows :(1)To realize a transmission window above the absorption band,the transmission line models are studied in this subject.Three guiding equivalent circuits,that features pass-bands at high frequencies,are investigated.Firstly,the paralleled lumped elements are employed to insert a transmission band within the wide-band absorption.Secondly,to improve the transmission efficiency and reduce the complexity of the structure,two designs with distributed resonators are proposed.Within the transmission window above the stop-bands,the electric dipole moment can be canceled by the distributed resonators,and the single-and dual-pass bands above the absorption bands are obtained by these structures.Finally,the presented theory is validated by numerical simulations and experimental measurements.(2)Based on the multi-resonant periodical structures,the continuous absorption behavior of the transmissive artificial electromagnetic absorptive structure is investigated.The resonances,which could be used to fulfill passbands for typical designs,are employed in these works to improve the absorpt ion performance.Firstly,an artificial electromagnetic structure with two pass-bands is designed.Its resonant power within the higher pass-band is absorbed,and the continuous stop-band and band-pass transmission window are achieved.Secondly,an absorptive structure with the wide-band transmission is proposed based on the modal interaction pole.The resonance with the band-pass response is used to fulfill a tri-resonant wide-band absorption within the low frequencies.Moreover,a dual-polarized design based on the second-order spatial filter is studied to improve the wide-band transmission,absorption,and reflection reduction performances.Finally,the proposed designs are validated by a good agreement between the numerical simulations and experimental measurements.(3)To further improve the transmission coefficient and reduce the structural complexity,the effect of electromagnetically induced transparency is studied.Firstly,the theory of two-pathway excitations is explored to investigate the operatin g mechanism of the atom electromagnetically induced transparency system.Secondly,the response of the electromagnetically induced transparency-like effect is mimicked by calculating the absorption power of the spring dual-oscillator system,which is employed as the theoretical basis for the structural design.Furthermore,the coupling generated by the proposed structure is employed to achieve destructive interference behavior.Thus,the lossy bright resonator is suppressed within the pass-band,which gives rise to a transmission window with a lower insertion loss.Finally,the structure based on the electromagnetically induced transparency-like effect is fabricated and measured,and the feasibility of applying this technology to the transmissive artificial electromagnetic absorptive structure is validated.