This communication addresses the maximization of the directivity from a radiating aperture through the derivation of a closedform expression for the modal field amplitudes whose field distribution at the aperture maximizes the directivity in a desired direction. This closedform expression arises from a convex formulation of the maximization problem (as a ratio of two Hermitian forms), which mathematically ensures that the achieved directivity value is the global maximum for a specified number of propagating modes. The proposed technique, which is valid for any aperture shape and polarization, is discussed and compared with previous work. Several numerical examples considering different main lobe directions, aperture geometries, and polarizations are presented. To verify the numerical results, radiation patterns and directivity values are computed using both commercial tools and in-house developed software.
This work presents the design and manufacturing of a K‐band reconfigurable phase shifter completely implemented in waveguide technology for reduced insertion loss, good matching, and large phase shifting range. The device is based on the combination of a short slot coupler and two tunable reactive loads implemented as a section of short‐circuited waveguide where an adjustable metallic post is inserted. Three prototypes of this design have been manufactured using different techniques (conventional computer numerical control machining, a low‐cost fused filament fabrication technique and direct metal laser sintering) in order to assess its performance for different applications. The prototypes have been characterized experimentally and the achieved results are evaluated and compared. The proposed phase shifter, since it is fully developed in waveguide technology, eliminates the need of adding transitions to planar structures in order to integrate lumped components like pin diodes or varactors. Therefore, this device has a great potential in high‐power beam steering phased arrays.
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