Circular Patch Array Absorber Design for Oblique Incidence by Using Winding Ratio Model of Transformer

This paper proposes a design method of a circular patch array absorber for oblique incidence by using an equivalent circuit with a transformer. In the equivalent circuit with the transformer, a matching angle of the absorber can be determined by using the winding ratio of the transformer. Hence, a calculation model for obtaining an arbitrary winding ratio of the transformer by using an arrangement period (winding ratio model) is developed. The winding ratio calculated by using the developed model is agreement in with that of simulated by using an electromagnetic (EM) simulator. The absorbers for 30° and 45° at 5 GHz are designed by using the developed model, and the incident angle characteristics of the designed absorbers are measured. As the result, the measured and the simulated matching angle are agreed within 5°. Therefore, the validity of the proposed method is indicated.