Research On Absorbing Properties Of Wave-absorbers With LHM And RHM Structures

With the development of modern technology, microwave absorbing materialsare becoming increasing important in both military and civil application fields.The main goal in the wave-absorbing materials research area is to increase theabsorption of the materials so that let the stealth structures be lighter, thinner andmore effective. Both theoretical and experimental evidences show that theabsorber will have better wave-absorption properties at the working frequency ifsuitable electromagnetic parameters' combination is formed, which is called thatthe parameters are matched.In 1968, Ex-Soviet Physicist Veselago reported his theoretical study results ofthe electrical dynamic properties of the medium with both negative permittivityand permeability and named this kind of material as left-handed material(LHM),and predicted that the wave vector (?), the electric field vector (?), and themagnetic field vector (?) in this material will form a left-handed system. In2001, this idea was experimentally verified by D.Smith, etc. Whenelectromagnetic wave propagating in the LHM, there will be some magicalphenomena, such as negative refraction, reversed Doppler effect and reversedCherenkov radiation etc.Our research results predict that when LHM is combined with conventionalRHM to form a LHM-RHM double-layer structured absorber, the reflection lossof it will be increased and the absorbing band will be widened. This indicatesthat the LHM is hopeful to be one of the wave-absorber composing materials,which has better wave-absorption properties.In this paper, four wave-absorber models containing LHM are proposed,including air/LHM/metal, air/LHM/RHM/metal, air/RHM/LHM/ metal andair/LHM/LHM/metal structures. The valuation laws of electromagneticparameters for the aim that absorber has better absorbing properties aretheoretically analyzed using a transfer matrix method (TMM). The structures'parameters are optimized employing a genetic algorithm. The absorbing properties of the four absorbers mentioned above and the effects of the LHM'sparameters in each absorber on the wave-absorption properties in the frequencyrange from 8GHz to 12GHz are investigated and simulated using a transmissionline model.The results show that the air/LHM/RHM/metal structure has the bestabsorbing property among four absorber structures; among the 3 double-layerabsorbers, the influences of LHM's electromagnetic parameters on the absorbingproperties have different varying trends, which is relative to the valuation ofRHM's parameters, in different parameter valuations; as the increasing of theLHM's thickness, the peak values of the absorption curves will change and thecorresponding frequency will also move towards lower frequency directions inthe absorbers(except LHM-LHM structure).There is few report about LHM used in absorbing material or absorber designareas can be found. Therefore, it is hoped that this work might be somereferences for the researchers working in the LHM or wave-absorbing materialsfields.