Browsing by Subject "Antenna phased arrays"

Now showing 1 - 7 of 7

Open Access
Design and analysis of slotted sectoral waveguide array antennas embedded in cylindrically stratified media
(IEEE, 2014-07) Kalfa, Mert; Ertürk Vakur B.
Slotted waveguide antennas are being widely used in military and commercial applications for many decades. Low cross-polarization, high power capacity, ease of fabrication in microwave bands, and the ability to form arrays make them excellent candidates for phased array antennas in radar applications. However, due to slots being highly resonant (narrow-band, high Q) radiators, their design parameters are very sensitive; hence, accurate design and analysis methods are required for a successful antenna design. Moreover, slotted waveguide array antennas are low-profile structures, which makes them suitable candidates for conformal and structure-integrated applications. Conformal and structure-integrated system solutions are especially required for air platforms, where aerodynamics, radar cross-section (RCS) and efficient use of real estate are of utmost importance. Although the accurate and efficient design and analysis of low-profile conformal slotted waveguide arrays are of great interest, available solution methods in the literature usually suffer in terms of efficiency and memory requirements. Among the available solution methods, one of the widely used solvers are integral equation (IE) based ones that utilize the method of moments (MoM). However, IE solvers suffer from long matrix fill times, especially for matrix entries related to the cylindrically stratified media. © 2014 IEEE.
Open Access
Efficient analysis of large phased arrays using iterative MoM with DFT-based acceleration algorithm
(John Wiley & Sons, Inc., 2003) Ertürk, V. B.; Chou, H-T.
A discrete Fourier transform (DFT)-based iterative method of moments (IMoM) algorithm is developed to provide an O(Ntot) computational complexity and memory storages for the efficient analysis of electromagnetic radiation/scattering from large phased arrays. Here, Ntot is the total number of unknowns. Numerical results for both printed and free-standing dipole arrays are presented to validate the algorithm's efficiency and accuracy.
Open Access
Fast acceleration algorithm based on DFT expansion for the iterative MoM analysis of electromagnetic radiation/scattering from two-dimensional large phased arrays
(IEEE, 2002) Ertürk, Vakur B.; Chou, H. T.
An acceleration algorithm based on Discrete Fourier Transform (DFT) is developed to reduce the computational complexity and memory storages of iterative methods of moment (IMoM) solution to O(Ntot), where Ntot is the total number of elements in the array. As such, numerical results for free-standing dipoles obtained using IMoM-DFT approach are presented and compared with the conventional MoM solution.
Open Access
Fast algorithm for scattering from planar arrays of conducting patches
(Institute of Electrical and Electronics Engineers, 1998-04) Gürel, Levent; Chew, W. C.
A direct (noniterative) algorithm for the solution of the electromagnetic scattering from three-dimensional planar arrays of conducting patches is developed. For an N-unknown problem, the computational complexity of this new solution technique is shown to be O(N2 log2N), which is considerably lower than the O(N3) computational complexity of the conventional direct solution techniques. The advantages of the reduction in the computational complexity is pronounced in the solution of large electromagnetics problems, such as scattering from large and finite arrays of patches, synthesis and analysis of finite-sized frequency selective surfaces (FSS's), and radiation and scattering from large phased-array antennas, to name a few.
Open Access
A new method for the prognosis of scan blindness angle in finite phased arrays of printed dipoles
(IEEE, 2011) Avser, Bilgehan; Erturk, Vakur B.
Scan blindness phenomenon is studied for finite phased arrays of printed dipoles on grounded planar dielectric slabs. A new method for predicting the scan blindness angles using the average scan impedances of a subsection of dipoles at the center of the array is introduced. A hybrid method of moments/Green's function technique is used to analyze the finite arrays of printed dipoles. Several numerical results are presented to demonstrate the accuracy of the new method in terms of predicting the blindness angle. © 2011 EurAAP.
Open Access
A parametric analysis of finite phased arrays of printed dipoles on large circular cylinders and comparisons with the planar case
(IEEE, 2004-06) Güner, B.; Ertürk Vakur B.; Bakır, O.
A parametric study of finite phased arrays of printed dipoles on electrically large coated cylinders is performed using a spatial domain hybrid MoM/Green's function technique. Dipole currents and several performance metrics like active reflection coefficient and input impedances of the dipoles are calculated and compared with their planar counterparts. The effects of the curvature, dipole orientation and changes in the array and host body parameters are observed and discussed.
Open Access
Phase-only beam synthesis by iterative semidefinite relaxations with rank refinement
(IEEE, 2013) Alp, Yaşar Kemal; Arıkan, Orhan; Bayri, A.
In phased array antennas, by varying the complex element weights beam patterns with desired shapes can be synthesized and/or steered to desired directions. These complex weights can be implemented by using amplitude controllers and phase shifters at the system level. Since controlling the phase of an RF signal is much easier than controlling its power, many systems do not have an individual amplitude controller for each element. Hence, beamshaping and steering are to be achieved by varying only the element phases. In this work, a new approach is proposed for phase-only beam synthesis problem. In this approach, the phase-only beam synthesis is formulated as a non-convex quadratically constrained quadratic problem (QCQP). Then, it is relaxed to a convex semidefinite problem (SDP), which generally provides an undesired high rank solution. An iterative technique is developed to obtain a rank-1 solution to the relaxed convex SDP. Conducted experiments show that, proposedmethod can successfully synthesize beam shapes with desired characteristics and steering directions by using only the element phases. © 2013 EURASIP.