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Electromagnetic Scattering Concepts Applied to the Detection of Targets Near the Ground
Problems related to the detection of targets in the presence of clutter and ground are investigated. The two basic problems are the change in the target response due to the presence of the ground and the recognition of the target response when contaminated with clutter return. The transient fields of short dipoles in the presence of a dielectric half-space are examined and exact closed-form solutions are obtained for some particular source and observation points. The solution for the case of the source and observation points coincident is used to determine the interaction between a dipole source and the interface and the resultant dipole impedance change. The same solutions are used to compute the change in the dipole modes of scatterers due to the presence of a half-space, particularly the shift in the s-plane poles of the target. Results are presented for both dielectric and perfectly conducting half-spaces. (Author).
Stationary Principles for Operator Equations with Applications to Electromagnetic Theory
An approach is investigated which, starting from differential or integral equations, leads to stationary forms of expressions for certain quantities such as the self-impedance of an antenna, the radiation pattern, etc. For certain simple geometries, not necessarily separable, it is shown that it is possible to obtain an improvement for the unknown field itself. (Author).
Radio Propagation in the Urban Scenario
This practical book provides fundamentals of electromagnetic wave propagation and its unique application for the design of mobile wireless systems in complex urban environments. It supplies telecommunication engineers with the proper theoretical and practical tools to: plan radio coverage in cellular networks; design a radio link; predict connectivity in a wireless network and ensure that the system to be designed fulfills regulations on exposure of general public to electromagnetic fields. You’ll understand the latest propagation models and be equipped to address the challenges facing wireless propagation for the most recent 5G mobile systems, including how to cope with new propagation sc...
Investigation of Use of Superimposed Surface Wave Modes
A method of achieving a matched aperture in phased arrays over a wide range of scan angle has been investigated. This method uses two or more propagating modes in each array element such that the reflections of these modes from the array aperture produce a cancellation effect at the element driving terminal. An experimental 256 element planar array was constructed to demonstrate this technique. Each radiating element consists of an open-ended waveguide driven by an end-on coaxial transition. Modal amplitude control of higher order modes is accomplished by means of either a perforated dielectric slab or an inductive iris at the aperture. (Author).
Investigation of Characteristics and Practical Implementation of Arbitrarily Polarized Radiators in Slot Array
The feasibility of the method of obtaining arbitrary polarization in both one and two-dimensional waveguide slot arrays was demonstrated. The arbitrarily polarized radiating element consists of a pair of cross slots which are cut in the sidewall of a bifurcated rectangular waveguide. Vertical and horizontal polarizations are excited by the sum and difference modes, respectively, in the bifurcated waveguide. By super-imposing the sum and difference modes in the proper amplitude and phase, any arbitrary polarization can be synthesized. (Author).
Identification of Radar Targets by Pattern Recognition
The problem of identifying radar targets without predetermined knowledge or measurements of their aspect angle is examined. The proposed solution is to use radar magnitude and phase versus frequency data in the resonance region as input data for pattern recognition techniques. Practical methods are developed for measuring radar phase and dealing with polarization effects. Pattern recognition algorithms that optimize separation between pairs of input data are developed. These algorithms are based on digital spatial frequency filtering of curves of the radar return versus the radar frequency. The technique is simulated on a digital computer for three objects - a cylinder, a cone, and a step cylinder - all of about the same size. Results show that at most aspect angles, satisfactory recognition is attained at moderate signal-to-noise ratios.
