All-metallic near-field convergent lens design using cross-Jerusalem-slot elements

The near-field convergent lens has aroused wide attention in the field of microwave passive imaging, medicine, and beam shaping in recent years as it can converge electromagnetic energy with high efficiency. The main objective of the paper is to exhibit the design process of a multiple-conductor-layers convergent lens using all-metallic elements. A quad-layer metal cross-Jerusalem-slot structure is proposed to obtain compact unit cells without dielectric substrate, and then an all-metallic near-field convergent lens based on the cells is constructed. To validate the proposed method, an L-band lens sample with 20 x 20 cells is designed and numerically simulated. Results show that the waves radiated from a horn antenna to the lens are focused in the near-field area, 500 mm away from the lens, with the full width at half maximum of the focal spot of less than 200 mm. In addition, it is observed that the overall size of the lens has a significant effect on the near-field convergent performance. Therefore, when the array is small, how to adjust the type of array elements to achieve a better convergence effect is analyzed in detail.