An optimisation framework for near field multifocusing on antenna arrays is proposed. Its aim is to obtain the feeding weights that must be applied to the elements of the array so that the antenna focuses on two or more targets simultaneously. The method is based on the definition of a proper cost function, which is minimised using an optimisation algorithm over an equivalent least squares problem. The success of the technique is noted in the fact that different array parameters can be obtained: magnitude and phase of the array elements or only phase synthesis. In order to show the efficiency of the method, several tests are carried out using different arrays and optimisation parameters. The simulation, manufacture and measurement of an 8 × 8 planar array able to focus on two different targets is also performed. Results show how the framework can be applied to general arrays and demanding requirements, so it may be easily extended to different synthesis problems besides multifocusing.

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In this letter, we demonstrate that the dispersion properties of printed double-sided parallel-strip lines can be controlled by using glide symmetry. Glide symmetry is introduced in with corrugations in both strips of a double-sided line. We demonstrate that glide symmetry eliminates the stopband between first and second propagating modes and yields to a higher propagation constant, preserving its linearity and the broadband nature of the underlying guiding technology. Thus, the glide-symmetric double-sided line can be designed to possess a high equivalent refractive index in an ultra-wide range of frequencies. These exceptional properties have been numerically and experimentally validated. Finally, we demonstrate the possibilities of this technology with a specific design, a glidesymmetric double-sided parallel-strip line with filtering properties. Potential applications are low-dispersive leaky wave antennas, electromechanical tunable phase shifters and filters.

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