An Ultrathin 2-bit Near-Field Transmitarray Lens

A novel ultrathin near-field (NF) 2-bit 24 × 24element transmitarray lens working at X-band is presented in this letter. The aim of this antenna is to focus in a point located in the NF without using any complex feeding network. In order to obtain a planar lens with a very low profile, a 2-bit-design approach is used to diminish the number of layers used in the structure. The simulations have been done using a model based on the concept that the NF of an array can be calculated as the sum of the far-field contributions of every single one of its elements. These are considered as plane apertures over which the tangential electric field is constant. In order to validate the results of this model, they are compared to both those obtained with a full-wave commercial software and those from measurements. Thus, an NF antenna is manufactured and measured showing the measurements' good concordance with the results of the model.