Browsing by Author "Yildiz, Hayrullah"

Now showing 1 - 4 of 4

Beam Steering of Vortex Waves by A Phased Array Based on The Field Equivalence Principle
(2022) Hizal, Altunkan; Yildiz, Hayrullah
A further ability can be added to an existing phased array (PA) to include generation and steering of noncollimated or collimated electromagnetic (EM) vortex waves (VW). The concept is based on the EM field equivalence principle. The near field of VW's generated by a uniform circular array (UCA) is calculated on a tilted planar finite size reference aperture (RAP) which intercepts all the VW modes. Using the Love equivalence principle and the fields of UCA on the RAP, the VW's are calculated in the far field. RAP is divided into small rectangular subapertures (SAP), simulating the elements of a PA. The UCA-fields on each SAP, for a given RAP's tilt angle (steering angle) are calculated. These fields are to be generated by rightly polarized PA's antenna elements fed by the associated transmit-receive modules. The method is also applied to VW's tightly collimated by a paraboloidal reflector. Numerical simulations obtained verified this concept.
Ka Band Far Field Radio Link System Based on OAM Multiplexed Vortex Beams Collimated by a Paraboloidal Reflector
(2021) Hizal, Altunkan; Yildiz, Hayrullah
Electromagnetic vortex-waves (VW) have linear azimuthal-phase, orthogonality in azimuth and orbital-angular-momentum (OAM). The VW-pattern has a null along the vorticity-axis and the cone-half-angle (CHA) and the beam-width (BW) expands with the OAM mode number p. Here, we collimated all p-VW-beams into a radiation cone (Rcon) with a small CHA and BW using a paraboloidal reflector (PaR) fed by a VW uniform-circular-array (UCA). We multiplexed all the transmitted (TX) +/- p-modes, each modulated by a 16QAM symbol-vector. We receive (RX) the TX-signal by p(max) number of nonvortex PaR antennas placed on a small arc of the Rcon. The RX-signal is cast into the standard discrete-Fourier-transform (DFT) format, using the beam-collimation, the azimuthal-orthogonality and zero-padding. The demultiplexing is performed by IDFT. The UCA is designed at Ka-band using circular microstrip-patch-antennas (msPA). The +/- p-modes are TX'ed by orthogonally-polarized separate msPA's. The effects of coupling of +/- p-modes, the calibration inaccuracies and signal-to-noise-ratio (SNR) are simulated by the Monte-Carlo method. It was found that the SNR is very high and the far-field radio-link is feasible. The bit rate of the present OAM-16QAM radio-link is increased by a factor of 2 p(max).
Space Time Coded Vortex Waves for Angular Target Localization
(2021) Yildiz, Hayrullah
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.
X-Band Radar for Simultaneous Multiple Target Localization Based on Collimated Vortex Waves
(2022) Hizal, Altunkan; Yildiz, Hayrullah
Electromagnetic vortex waves (VW) generated by a uniform circular array (UCA) are tightly collimated by a paraboloidal reflector into a radiation cone with a small vertex angle and beam-width. This antenna system is used in a conceptual design of a medium range X-band high resolution radar sensor for localization of multiple targets simultaneously. Its features, including the performance with clutter and ground multipath, are comprehensively analyzed yielding novel results. The VW based algorithms for range and angular localizations of multiple targets are given. The effects of the tolerances of the UCA element excitations are estimated. Results for Monte Carlo simulations for localizations and detection performance are presented.