More Synthetic Aperture Antennas (SAR) use dual-polarization slotted waveguide planar antenna for Earth Observation application in X-band. They are characterized by a pencil beam antenna with low side lobes levels, good cross-polarization discrimination and return loss over a 200 MHz bandwidth. The antenna design is challenging problem that involves the geometrical structure optimization to meet more than one requirement, so that a multi-objective optimization the suggested method to achieve the desired performance.
The vertical polarization (VP) is realized with a ridged-waveguide longitudinal slot linear antenna array, while the horizontal polarization (HP) is realized with an untilted narrow-wall slot linear array. To excite the narrow-wall slot different approaches have been considered, including inclined-wire or shaped-irises. Coupling effects between the VP and HP linear arrays have been included into the model.
The complete geometry definition should require over 100 independent variables, so that the possibility to optimize the antenna performance becomes very strong demanding. This represents a typical multivariable and multi-objective optimisation problem which has been resolved by modeFRONTIER approach using the powerful capabilities of the optimisation ambient. Individuation of the more sensitive variables has been an important step in the optimisation starting phase. A DOE (Design of Experiment) technique has been used to understand better the input-output relationship and to reduce the design space dimension (number of variables); then the multi-objective optimization has been carried out.
The achieved final structure meets the overall requirements with a very simple and regular geometry with robust design. The reduction of the size has been showed as a new solution with improvement on the antenna satellite allocation. The modeFRONTIER capabilities consent to obtain different RF solutions, which permit to individuate the more simple ones with respect to the manufacturing aspects.
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