Mechanical steering is the most affordable solution for scanning antennas. The challenge is to balance the trade-offs between high-gain, low profile and wide beam steering. We previously showed that for a Transmit-Array (TA) antenna wide elevation scanning can be achieved by moving the primary source along a line parallel to the aperture. However, aberrations build up as the displacement relative to the lens focus increases, limiting the overall scanning performance. In this work, a new approach to minimize these aberrations is presented. The design of the TA usually assumes an incident spherical wave front. Herein, instead of acting only on the phase correction of the TA, the feed illumination of the aperture is co-designed to minimize the aberrations for all feed positions. The adjustment of the feed illumination is achieved by placing a tailored dielectric lens in front of a standard horn antenna (primary feed). A 28 dBi TA antenna operating at Ka-band uplink [29.5, 30GHz] with F/D=0.7 and elevation scanning up to 50 degrees is designed. Full-wave simulations show an effective reduction of SLL (<; -20 dB) when compared with a conventional spherical illumination (< -12dB).

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