Design And Implementation Of Ultra-Thin And Ultra-Wideband Absorbing Structure

The use of wave-absorbing structures in military and civilian fields is becoming increasingly mature for applications such as stealth fighters,microwave anechoic chambers and so on.However,the deepening of research has revealed that traditional wave-absorbing structures cannot meet ultra-wideband,ultra-thin thickness and light weight engineering requirements.Metasurface technology greatly reduces the thickness of absorbing structures under the limitation of the Rozanov limit.On the other hand,absorbing structures loaded with non-Foster devices break through the Rozanov limit,widening the frequency band and reducing the thickness.In this thesis,non-Foster devices circuit characteristics,metasurface technology,and full-wave electromagnetic simulation methods are researched in deep.An ultra-thin and ultra-wideband absorbing structure is designed and implemented.The main work and contributions of this thesis are as follows:1.applying the equivalent circuit model methodology,an absorbing structure loaded with non-Foster devices is designed with the objective of adjusting the impedance matching within a certain frequency band.It is shown that with a thickness of 50 mm,an absorption rate larger than 90% within the frequency range 0.13 GHz to 1.3 GHz is achieved.2.applying the metasurface technology,an absorbing structure based on magnetic material loaded with a frequency-selective surface with the objective of adjusting the impedance matching of the overall absorbing structure is designed.It is shown that with a thickness of 6.84 mm,the absorption rate is larger than 90% within the frequency band from 1.7 GHz to 18 GHz.3.an iterative co-simulation methodology based on full-electromagnetic wave and circuital simulation platforms is developed to ensure the simultaneous optimization of electromagnetic model structures and circuital parameters.Furthermore,a parallel plate waveguide test platform methodology for measurement of absorbing structures is designed.4.by exploiting the negative impedance characteristic of non-Foster devices and the metasurface technology,an ultra-thin and ultra-wideband absorbing structure is designed by loading a frequency selective surface with a non-Foster device,and the whole structure is optimized with the proposed iterative co-simulation method.An absorption rate larger than 80% within the frequency ranges from 0.3 GHz to 1.2 GHz and from 2 GHz to 18 GHz,and larger than 70% within the bandwidth from 1.2 GHz to 2 GHz is achieved with a total thickness of 9.098 mm.The ultra-thin and ultra-wideband absorbing structure researched and designed in this thesis is able to widen the absorption bandwidth of the proposed structure while maintaining a limited thickness,making it valid for applications in stealth and electromagnetic compatibility technologies.