Design, modeling, and optimization of a mechanically reconfigurable smart reflector antenna system

In this research, a new design and operation methodology of a reconfigurable dual offset contour beam reflector antenna (DCBRA) using a mechanically adjustable subreflector is presented. Based on the Cassegrain configuration, the fixed main reflector with a diameter of 1.25m is shaped for the continental U.S. (CONUS) beam pattern and the smaller subreflector is initially set up to have a hyperboloidal cut shape with an elliptical aperture of 30 cm by 70 cm. The subreflector is made with a thin flexible material such that it deforms by movement of a certain number of linear point actuators attached on the back surface. With the deformable subreflector, the electromagnetic field illuminating the main reflector can be changed leading to a different far-field radiation pattern.; For the analysis, the finite element method (FEM) is applied to calculate the deformed shape of the subreflector from a given configuration and movement of actuators. The actuators are modeled as boundary condition and then the linear matrix equation is solved using LU decomposition technique. For the calculation of radiation pattern, Physical Optics (PO) is utilized for both the main reflector and the subreflector: PO-PO. After two separate codes are completed, a unified computation tool is developed by incorporating the PO-PO routine into the FEM code.; For optimal and minimal usage of the actuators, two independent optimization problems are solved: Optimization of actuator placement and optimization of actuation values. Several actuator placement optimization techniques are proposed and implemented in the code. After actuator positions are determined, the optimal actuation value of each actuator needs to be determined. The objective function is defined as the sum of the squared error between the actual antenna gain and the desired gain at each point falling inside of a geometrical boundary in the u-v space. When implemented, it was observed that the Cyclic Coordinate Search method performs the best.; Finally, as an example, generation of contour beams for four different geographic regions—CONUS, Australia, Brazil, and Afghanistan—is presented. The effect and result of various actuator placement optimization techniques are also presented and discussed.