Rajendra K. Arora

Bio: Rajendra K. Arora is an academic researcher from Florida State University. The author has contributed to research in topics: Surface wave & Magnetic field. The author has an hindex of 11, co-authored 56 publications receiving 364 citations. Previous affiliations of Rajendra K. Arora include Florida A&M University & Indian Institutes of Technology.

Optimal Thinning Levels in Linear Arrays

Abstract: There exist many methodologies for the thinning of linear arrays, each with its advantages and disadvantages. Instead of presenting a new method, this communication presents actual lower bounds to attainable results and estimates lower bounds for more complex cases. When feasible, results were obtained through an exhaustive search of the solution space. When this was not possible, binary particle swarm optimization was used.

Synthesis of unequally spaced arrays using dynamic programming

Abstract: The application of dynamic programming to the synthesis of unequally spaced symmetrical antenna arrays is further investigated. The design criterion is to obtain a combination of elements, in a quantized aperture which has the lowest value of the peak sidelobe level over a specified angular interval. A 25- element array in an aperture length of 50\lambda is synthesized, and it is shown that the designs obtained are considerably superior to those obtained by other investigators using different techniques.

Guided Waves on a Planar Helix

Abstract: Considered here is a planar structure comprising a pair of parallel arrays of periodically spaced conducting strips which conduct in different directions in the two arrays. The guiding properties of this planar structure are found to be similar, in one case, to those of circular tape helices. While in general, different dielectric media are assumed in the sandwiched and outer regions, the special cases studied are 1) the case in which air constitutes both the media, 2) the normal-helix case in which the inner medium is a solid dielectric and the outer medium is air, and 3) the "inverted-helix" case with the two media interchanged.

Coupled Slot Line Field Components

Abstract: The paper presents expressions for the odd- and even-mode electric field components and the magnetic field components in the air and dielectric regions of the coupled slot line structure. These expressions are numerically computed and the fields in the cross section and the longitudinal sections are illustrated.

Synthesis of unequally spaced arrays by simulated annealing

Abstract: Simulated annealing is applied to the synthesis of arrays in order to reduce the peaks of side lobes by acting on the elements' positions and weight coefficients. In the case considered, the number of array elements and the spatial aperture of an unequally spaced array are a priori fixed. Thanks to the high flexibility of simulated annealing, the results obtained for a 25-element array over an aperture of 50/spl lambda/ improve those reported in the literature.

Antenna Subset Modulation for Secure Millimeter-Wave Wireless Communication

Abstract: The small carrier wavelength at millimeter-wave (mm-Wave) frequencies enables featuring a large number of co-located antennas. This paper exploits the potential of large antenna arrays to develop a low-complexity directional modulation technique, Antenna Subset Modulation (ASM), for point-to-point secure wireless communication. The main idea in ASM is to modulate the radiation pattern at the symbol rate by driving only a subset of antennas in the array. This results in a directional radiation pattern that projects a sharply defined constellation in the desired direction and expanded further randomized constellation in other directions. Two techniques for implementing ASM are proposed. The first technique selects an antenna subset randomly for every symbol. While randomly switching antenna subsets does not affect the symbol modulation for a desired receiver along the main direction, it effectively randomizes the amplitude and phase of the received symbol for an eavesdropper along a sidelobe. Using a simplified statistical model, an expression for the average uncoded symbol error rate (SER) is derived as a function of the observation angle. To overcome the problem of large sidelobes in random antenna subset switching, the second technique uses an optimized antenna subset selection procedure based on simulated annealing to achieve superior performance compared with random selection. Numerical comparisons of the SER performance and secrecy capacity of the proposed techniques against those of conventional array transmission are presented to highlight the potential of ASM.

Synthesis of Sparse Arrays With Focused or Shaped Beampattern via Sequential Convex Optimizations

Abstract: An iterative procedure for the synthesis of sparse arrays radiating focused or shaped beampattern is presented The algorithm consists in solving a sequence of weighted l1 convex optimization problems The method can thus be readily implemented and efficiently solved In the optimization procedure, the objective is the minimization of the number of radiating elements and the constraints correspond to the pattern requirements The method can be applied to synthesize either focused or shaped beampattern and there is no restriction regarding the array geometry and individual element patterns Numerical comparisons with standard benchmark problems assess the efficiency of the proposed approach, whose computation time is several orders of magnitude below those of so-called global optimization algorithms

Stochastic optimization of linear sparse arrays

Abstract: In conventional beamforming systems, the use of aperiodic arrays is a powerful way to obtain high resolution employing few elements and avoiding the presence of grating lobes. The optimized design of such arrays is a required task in order to control the side-lobe level and distribution. In this paper, an optimization method aimed at designing aperiodic linear sparse arrays with great flexibility is proposed. Simulated annealing, which is a stochastic optimization methodology, has been utilized to synthesize the positions and the weight coefficients of the elements of a linear array in order to minimize the peak of the sidelobes and to obtain a beam pattern that meets given requirements. An important novelty is the fact that the latter goal can be achieved in parallel to the minimization of both the number of elements and the spatial aperture, resulting in a "global" optimization of the array characteristics. The great freedom that simulated annealing allows in defining the energy function to be minimized is the main reason for the notable versatility and the good results of the proposed method. Such results show an improvement in the array characteristics and performances over those reported in the literature.

Dipole mode electromagnetic waveguides

Abstract: A new form of waveguide is described which can support propagation of electromagnetic waves in the dipole mode. The waveguide is coaxial with inner and outer members having cylindrical surfaces separated by a dielectric. The longitudinal and transverse impedances of these surfaces and the dielectric material are such that propagation in the dipole mode is possible. Structures having the necessary surface impedances are described. Apparatus for launching the dipole mode and extracting power from it are also described.