Space Time Coded Vortex Waves for Angular Target Localization
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Vortex waves (VW) carrying orbital angular momentum (OAM) have orthogonal azimuthal modes described by the topological charge p. The orthgogonality of OAM modes leads to azimuth localization of multiple targets. A pulsed radar architecture based on phased array (PA) positioned along the z axis (zPA) with VW uniform circular array (UCA) as its elements is described for simultaneous range, polar and azimuth angular localizations of radar targets. The zPA is focused to the peaks of VW patterns for narrow beams and low side lobes. For angular localization of targets in the same range-Doppler cell, an intrapulse multiple transmit (TX) and multiple receive (RX) scheme associated with multiple p's is described. The radar pulse is divided into subpulses as many as the maximum value of p. In each subpulse, we TX by p and RX with +/- p. The range(r) localization, which uses (-p) RX, is based on the intrapulse topological charge and polyphase code pulse compression by cross-correlation RX. The multiple elevation (polar -theta) localization, which also uses (-p)RX, is based on monopulse processing of the highest signal-to-noise ratio responses. The azimuth (phi) localization pertinent to each theta uses (+p) RX and form a transform in phi domain. A full PA using UCA and zPA in RX is also described to increase the accuracy of the angular localizations. The elements of UCA are highly phi symmetrical microstrip circular patch elements An S band radar example is given to assess the performance of the localization algorithms.