Study On The Electromagnetic Nonlinear Effect Based On The Electric Field Enhancement And Backward Wave Characteristics Of Metamaterials

Metamaterial is an artificial medium for artificial periodic arrangement design.It has been paid more and more attention by researchers because of its unique properties which are not available in nature.Electromagnetic materials research is interdisciplinary,involving electromagnetic,solid physics,electronics,semiconductor technology and other fields.Nonlinear metamaterials are important parts of metamaterials.In order to control the properties of the metamaterials,the nonlinear characteristics of metamaterials must be systematically investigated.In this paper,the nonlinear effect of power modulation on the resonant frequency is studied firs and then discusses the other aspects of the nonlinear effect,second harmonic enhancement in double resonance mode.Finally,the nonlinear effects of metamaterials are further studied,and the second harmonic enhancement based on backward wave is discussed.This paper has gradually explored the nonlinear effects of metamaterials and the main contents include the following three points:(1)The electro-resonant ELC metamaterial structure is used as the basic resonant unit cell,by adjusting the structure size to make it work in the S band.We demonstrate that the power has a modulation effect on the device designed in this paper by using the CST simulation software and Spice file.Then paste the varactor element welded to the opening resonance unit,which forms a whole structure of ELC unit cell.The experimental results show that the resonant frequency of the metamaterial structure shows a blue shift with the increase of the incident electromagnetic wave power.(2)A double resonance electromagnetic material is introduced,and the second harmonic frequency and the fundamental frequency satisfy the resonance condition at the same time.The results show that the double resonant mode can effectively improve the efficiency of the second harmonic generation of the metamaterials structure.When the incident electromagnetic wave power is 0 dBm,the energy of the reflected second harmonic obtained in the double resonant mode is higher 3 dB than that in the single resonant mode.(3)The method of controlling the radiation direction of the second harmonic by using the backward wave characteristic of the second harmonic is discussed.Two kinds of structures commonly used in the field of metamaterials are selected.Combined with the model file of the varactor diode,and a frequency point is selected in the left hand frequency domain of the metamaterials so that it just satisfies the phase match condition.The four-layer structure is obviously different from the single-layer structure.The second harmonic power reflected in the range of-20 dBm to 20 dBm is larger than that of the transmitted second harmonic.The results show that the structure of our design is reasonable and the method of phase matching can be used to increase the power of the second harmonic,namely reflection enhancement.