Variable Angle Test Of Dielectric Properties Of Curved Wave Permeable Materials

Curved surface materials with microwave transmission properties have a wide range of applications in the field of microwave,such as the head design of civil aircraft,detection rockets,observatories and so on will use the curved surface materials to protect its internal radar antenna.Dielectric property is one of the important parameters of materials,which reflects the wave-transparent properties of materials.It can be seen that the dielectric properties of curved surface wave-transmitting materials are of great significance for the design of curved surface materials and the analysis of the working environment of its internal radar antenna,especially for the aerospace field that requires high precision.This thesis mainly studies the testing technology of dielectric properties of curved surface wave-transmitting materials with variable angle.After understanding the research trends of dielectric parameters testing technology of curved surface materials at home and abroad,it is determined that the purpose of this thesis is to propose a set of test methods that can be applied to curved surface dielectric,rather than generally apply the dielectric calculation method of plane materials to curved surface,and provide a set of system that can be used to test the dielectric properties of curved surface materials with variable angle.In order to achieve the above purpose,this thesis first establishes the test model of curved surface materials,analyzes the plane wave oblique incidence theory,and establishes the relationship between the plane and the surface based on the local oblique incidence theory,so as to derive the formula for calculating the insertion loss of curved surface materials,and invert the dielectric parameters of curved surface materials.Then,in order to ensure the test accuracy,the calibration method needed in the test process is studied,and the corrugated horn antenna with circular symmetry and extremely low sidelobe is developed.Since only the electromagnetic wave through the curved surface material needs to be collected,the complete two-port calibration is not required in the calibration method,and the response calibration is adopted.The error sources of response calibration are analyzed,and the air line compensation method for the curved surface area is given.After determining the calibration method,the corrugated horn antenna and the moment-circular transition are designed and developed,and the nearfield scanning system is built to test the antenna performance.Finally,a variable angle test system is built to test the dielectric properties of acrylic materials with wave transmission performance.The test results are given and the error sources are analyzed.The dielectric properties of various regions of curved surface materials can be effectively tested by using the research method of curved surface and the variable angle test system in this thesis,which provides technical support for the design of curved cover and other components.Through the above systematic research,this thesis uses the curved surface air compensation after response calibration to complete the variable angle insertion loss test of cylindrical acrylic in Ku band,and uses the established curved surface test model to successfully invert the tangent of dielectric constant and loss angle of cylindrical acrylic,which proves the feasibility of local plane equivalence of curved surface wave transmission materials in free space dielectric test.