Investgation On Broadband Transparent Microwave Absorber Based On Grid-like Metal Ground

With the development of modern science and technology,various electronic devices have sprung up like bamboo shoots after raining.At the same time,they will also bring a lot of electromagnetic wave radiation.Electromagnetic interference caused by electromagnetic wave radiation will not only affect the normal operation of various electronic equipments,but also do damage to our health.However,the printed circuit board（PCB）structure used in the traditional microwave absorber structure often has an opaque all-metal ground layer in order to prevent the transmission of electromagnetic waves.This structure makes it impossible to meet the needs of good transparency.requirements,it cannot be used in some application scenarios that require transparency,such as in glass buildings.Therefore,this paper proposes a transparent microwave absorber based on grid-like metal ground to meet such a requirement.This paper proposes different structures for different application scenarios,which can satisfy the absorption or absorption-transmission-absorption characteristics in a specific frequency band.The main work is as follows:（1）To form a transparent microwave absorber,the traditional process of printing the structure on the PCB board should be converted into printing on a transparent resin,and the all-metal surface as the ground plane should be converted into a grid-like metal layer as the ground plane,The grid-like metal layer adopts a structure composed of uniform metal thin wires.This paper mainly introduces a structure that is equivalent to an all-metal surface at low frequencies and a band-pass structure.Using the screen printing technology,the samples were fabricated,and the samples were tested by the space transmission measurement method,and the design was further verified.（2）Based on the traditional double ring structure,a transparent microwave absorber with full absorption in the frequency band of 1.92 GHz to 8.48 GHz is designed.The unit size of the structure is 24.3 mm,the relative bandwidth of the structure’s absorbing frequency band is 126.15%,and the electrical thickness is 0.091λ.If the application scene requires high transparency of the structure,a transparent nut can be used.The four sides of the structure are fixed.If a certain bearing capacity is required,that is,certain mechanical properties are required,the honeycomb structure can be printed by 3D printing technology for bearing.And starting from the equivalent circuit,the working principle of the structure is analyzed.Using 3D printing technology,a transparent resin material was printed as the medium layer,and the circuit structure was printed on the resin.The design of the structure was further verified by experiments.（3）Based on the traditional cross-slot type structure and miniaturized it,the cross-slot type is bent to design a miniaturized Swastika Structure and Terminal Bending Structure.The two structures are cascaded with a band-pass mesh metal ground.The swastika structure has a reflection coefficient|S₁₁|below-10 d B from 1.66 GHz to 6.37 GHz,a relative bandwidth of 117.3%,and a passband from 4.24 GHz to 5.33 GHz.The reflection coefficient|S₁₁|of the terminal bent structure is below-10 d B at 2 GHz to 6.32 GHz,and the pass band is from 4.3 GHz to 5.18 GHz.The structure was also processed and further verified by experiments.