Series Dual-Fed Continuous Transverse Stub Array With Enhanced Multibeam Operation Enabled by a Reflective Luneburg Lens

This article introduces an all-metal series dual-fed continuous transverse stub (CTS) array that enables multibeam operation at K-band. This capability is obtained using a reflecting Luneburg lens (RLL) beamformer made of two stacked circular parallel plate waveguides (PPWs). The bottom PPW hosts a graded index medium that collimates the rays coupled by a corner reflector to the top PPW, where the CTS array is located. This design capitalizes on the RLL’s rotational symmetry, using a circular array of feeds to generate multiple planar wavefronts that illuminate the CTS array across a 360° range. Consequently, a new series-fed CTS array has been introduced to ensure high aperture efficiency when excited from diametrically opposed ends. The appropriate selection of the feeds, combined with the rotation of the CTS plane, enables the generation of simultaneous independent beams with continuous scanning. This architecture enhances the capabilities of conventional variable inclination CTS arrays. A prototype has been fabricated and tested, demonstrating excellent performance between 17.3 and 21.2 GHz, with an aperture efficiency of 43.5%–58% and a radiation efficiency of 90%. The antenna achieves scanning up to 55° in azimuth and from 5° to 65° in elevation through port switching, and full-azimuthal coverage with the added mechanical rotation. This design is particularly significant for K-band low-earth orbit (LEO) high-throughput satellite communications (SATCOMs).