An improvement of the wide-angular scan-loss compensation (SLC) and sidelobe level (SLL) in a small linear array with 23 elements is discussed. The array integrates small subarrays with an optimized pattern for SLC, while the SLL suppression is obtained by using a combination of elements with phase steering only and elements with amplitude/phase control in the center. This combination leads to a less number of T/R module. When the antenna is scanned to ±60°, a maximum first and peak SLL (FSLL and PSLL) of -15.1 dB are obtained. In addition, a -4.6 scan-loss is obtained, it means that the SLC is 2.4 dB with a Cavity-backed U-slotted Patch (CUP) antenna. These performance results are very attractive in particular for a small linear array with wide angular scanning capability.

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A novel approach is proposed for building a planar array derived from linear arrays using a toolbox of different types of subarrays located parallel and perpendicular to the linear array axes. The array design assumes constant element patterns and focuses on rectangular array applications with one dimensional, wide-angular beam scanning. Optimization criteria concern a trade-off between side lobe level performance, directive gain scan-loss, reducing the number of element controls and maximizing the use of phase-only elements for beam steering. All subarray configurations and functionalities, for improving the full array performance in sidelobe level and scan-loss compensation, are analyzed and validated in detail. The step-by-step integration of different subarrays starts from the center part of the array. This center part is a linear subarray along the major axis of the rectangular array with uniform maximum amplitude and spatially stretched. This subarray is combined with cross-line subarrays perpendicular to this center axis. At both edges of the center array, two in-line, uniform-amplitude and stretched subarrays are added and combined with cross-line subarrays. The amplitude distribution of the 3 in-line subarrays and the cross-line subarrays allows for lowering the sidelobe level in the plane of scanning. Finally, at both ends of the three in-line subarrays, subarrays with two and five elements are applied for reducing the scan-loss. By assuming cos(\vartheta) element pattern results are given for a planar rectangular array with 41 elements length and 3 elements width. To lower cost and higher power efficiency, the array uses only 33 multi-bit phase shifters, 12 1-bit phase switches, and 4 attenuators for amplitude control. Optimized broadside and 60° scanning patterns are compared and show improved performance in directive gain D=24.4 dBi (broadside), D=19.9 dBi (60°) and in \text {SLL}=-21.6 dB (broadside), \text {SLL}=-19.5 dB (60°).

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An advanced design, adding a significant first sidelobes level (FSLL) improvement to a previously introduced wide-angular-scanning, linear array prototype with demonstrated scan-loss compensation (SLC) and sidelobes suppression features is discussed. The linear array makes use of in-line subarrays for SLC and an additional amplitude taper in its central, uniform region for lowering the FSLL with as much as 4\mathrm{d}\mathrm{B} at \pm 60 {\mathrm{o}} scanning (13\mathrm{d}\mathrm{B} at \pm 20 {\mathrm{o}} scanning). Several Taylor-type amplitudes tapers are compared, the best overall performance improvement being observed for a -18dB prototype taper. The advocated solution is highly suitable to high-sensitivity radars requiring a fast-scanning, fan-beam.

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The scanning performance of wide-angular scanning linear arrays is primarily degraded by the limited angular profile of the employed elements' patterns. This paper introduces an innovative strategy for compensating this degradation by using subarrays. Our design uses a uniform linear array with half-wavelength spaced elements, supplemented by subarrays that are symmetrically placed at its edges. The employed subarrays have controlled patterns, favoring some directions for effective scan-loss compensation (SLC) and suppressing other directions for lowering the sidelobes level (SLL). Two types of feeding configurations, making use of fixed power dividers in combination with 1-bit phase switch, are used for producing the desired patterns. The complete array design and physical validation, starting from the elements, continuing with the subarrays and ending with the system integration are also discussed in detail. The integration of the subarrays yields notable performance improvements at large scanning angles when compared with uniform linear arrays. The peak and first SLL of -14.1 dB, and the SLC of 2 dB are obtained when the array with CUP antennas as elements is scanned to the maximum scan angle direction.@en

A full-scale concept demonstrator for the scan loss mitigation via integrating subarrays in sparse, linear arrays is presented for the first time. The array uses technologically attractive cavity-backed, U-slot, patch antennas. An effective computational philosophy is proposed, validated and applied for a full electromagnetic characterisation of the resulting very large, non-uniform array. The computational results highlight impressive improvements when compared to the performance of sparse arrays comprising elementary radiators, exclusively. These results provide compelling arguments for the superiority of a physical concept demonstrator designed along these lines.

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A novel approach is proposed for compensating the scan loss in wide-angular scanning array antennas due to the pattern falloff of physical radiators. The method is based on replacing elements in (linear) arrays with sub arrays with enhanced radiation intensity at large angles. This strategy is best applicable in the case of sparse arrays that intrinsically provide the space for accommodating sub arrays. An optimised linear sub array, with 5 dB radiation intensity enhancement at 60° is designed. This sub array is then incorporated in linear array antennas with (approximately) 50% thinning factors. An up to 1.2 dB improvement of the maximum directivity at 60° beam scanning is obtained. The obtained results allow conjecturing that a similar strategy, when applied to planar arrays, will lead to an even more significant scan-loss reduction, this yielding a substantial performance enhancement for wide-angular scanning radar array antennas.

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