Synthesis of Orbital Angular Momentum Antennas for Target Localization

Abstract

The exploitation of Orbital Angular Momentum (OAM) is proposed to design circular‐support continuous aperture distributions and concentric‐ring arrays for target‐localization applications. The proposed approach allows generating a single isolated null of the field in the target direction, which is of interest with respect to common techniques leading to a line (or perpendicular lines) of power‐pattern zeroes in the spectral plane. In the presented design procedure, the optimal continuous aperture source is first identified by resorting to the most suitable OAM vortex and effective tools such as the Singular Value Decomposition of the involved operator and a smart Convex Programming optimization. Then, by exploiting fast deterministic algorithms, this continuous source is discretized into circular‐ring arrays emulating it at best. Relevant applications including equispaced arrays, sum‐difference reconfigurable arrays, and isophoric sparse arrays are presented. The proposed approach is also compared with the state‐of‐the‐art techniques and assessed through full‐wave electromagnetic simulations.

Four‐Beams‐Reconfigurable Circular‐Ring Array Antennas for Monopulse Radar Applications

“…In fact, Equation 3a follows the rules in , Bucci, Isernia, Morabito, Perna, and Pinchera (2009) where it is shown that the optimal aperture distribution for a pencil beam with maximum directivity is real, Equation 3b complies with (Battaglia et al, 2023b), and Equations 3c and 3d allow generating, by virtue of the symmetry of the array layout, the two difference patterns (Rocca & Morabito, 2015). It is worth noting that a-priori choosing the excitation phases is strictly required in order to make "convex" the constraints on excitation amplitudes which, in turn, is necessary in order to enable the optimal synthesis of phase-only reconfigurable arrays.…”

“…This is done by setting the values of M, Δρ, and Δϕ according to the requirements in terms of array size and overall number of elements, and also by taking into account some desired parameters for the different radiation patterns as, for instance, their beamwidth or divergence angle. Then, we choose the most suitable order of the OAM vortex, say 𝐴𝐴 l𝓁 , by following the guidelines in Battaglia et al (2023b) and perform an uniform discretization of the spectral variables as…”

“…To counteract such an issue, exploitation of Orbital Angular Momentum (OAM) vortex beams has been recently proposed (Battaglia et al., 2023b; Kou & Yu, 2022; Yu & Kou, 2022). In fact, this kind of fields generates a power pattern having a circularly‐symmetric behavior as well as a null at boresight or, better to say, a circularly‐symmetric difference pattern.…”

“…On the other side, while the traditional difference beams can quickly determine the azimuth and elevation angles of the target through a couple of one‐dimensional scans, the OAM difference patterns do not allow measuring the azimuth or elevation angles independently. Rather, they require a two‐dimensional scanning of the entire spectral domain, which may increase the time for locating the target (Battaglia et al., 2023b).…”

“…

To counteract such an issue, exploitation of Orbital Angular Momentum (OAM) vortex beams has been recently proposed (Battaglia et al, 2023b;. In fact, this kind of fields generates a power pattern having a circularly-symmetric behavior as well as a null at boresight or, better to say, a circularly-symmetric difference pattern.Notably, the single isolated null of the field in the target direction allows improving the target localization accuracy with respect to common techniques leading to lines of power-pattern zeroes in the spectral plane.

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