Analysis Of Electronical Performances Of Spaceborne Microstrip Array Antenna With Thermal Deformation

As the "eyes" and "ears " of the space communications, electronic countermeasures, navigation, environmental monitoring and other satellite systems, the spaceborne array antenna achieves a greater physical aperture through a deployable configuration. It has been one of the key equipments in the areas of aerospace without the many drawbacks brought by the mechanical scan antennas and it has great value in application and broad prospect in the future. As one of the main forms of spaceborne array antennas, the structure of microstrip array antenna deformed caused by the extreme temperature environment of the space. For the microstrip antenna with low profile, thermal deformation of microstrip array antenna not only includes the change of the position but also includes the change of the structure. To analyse the influence of thermal deformation of spaceborne microstrip array antenna, this paper conducts the research from the point of electromechanical coupling, it mainly includes the following aspects:Firstly, the characteristic and seven key technologies of the structure of spaceborne array antenna are introduced. A typical microstrip array antenna of X band at a frequency of 10 GHz is modeled and optimized, and achieving a spaceborne microstrip antenna element that the return loss is more than 20 d B.Secondly, for the antenna element, the electromechanical coupling model of the microstrip antenna element with the structure deformation(bending deformation) is established at the foundation of radiation properties of the microstrip antenna element, from the perspective of electromechanical coupling. By comparing with the simulation results of HFSS, the scope of the electromechanical coupling model is determined that the relative error of microstrip antenna element at X band is less than 5% when the coordinate central angle is less than 40°, which meets the engineering demands. Meanwhile the influence of the temperature on the structure of the spaceborne microstrip antenna is simulated and the influence of thermal deformation on the electrical performance of the antenna element is analysed by the electromechanical coupling model. The results show that with the increase of the temperature(100℃~120℃), the deformation increases, and the electrical performance decreases, the maximum reduction of the gain is 0.21 d B. With the decrease of the temperature(-140℃~-160℃), the deformation increases, and the electrical performance decreases, the maximum reduction of the gain is 0.42 d B.Finally, for the array antenna, the electromechanical coupling model including the changed shape, the offset position and the changed direction of the element is established by the theory of electromagnetic field on the basis of the electromechanical coupling model of the microstrip antenna element, and the electromechanical coupling model is verified by an example of 1×5 array antennas at X band under the structure without deformation and with bending deformation. The results show that the relative error between electromechanical coupling model and HFSS is less than 5%, which meets the engineering demands. Then the influence of the thermal deformation on the electrical performance of the spaceborne array antenna is analysed by the electromechanical coupling model. The results show that the gain decreases 0.27 d B, the sidelobe level increases 2.07 d B and the pointing direction changes 0.03° under the temperature of 120℃. The gain decreases 0.72 d B, the sidelobe level increases 3.98 d B and the pointing direction changes 0.3° under the temperature of-160℃. The gain decreases 0.18 d B, the sidelobe level increases 1.17 d B and the pointing direction is invariant under the temperature gradient of 20℃ to 70℃.