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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).
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).
Antenna Theory and Practice
This Book Has Been Designed For Both The Undergraduate And Postgraduate In Electronic Engineering, Electrical Communication Engineering And Electrical Engineering, And For The Postgraduate In Physics Specialising In Electronics. It Is A Compact And Comprehensive Text And It Stresses The Basic Principles Of Antenna Theory And Practice. Starting With Electromagnetics And The Theory Of Radiation Which Forms The Basis Of Antenna Theory, It Treats In Detail Different Types Of Antennas Like The Linear Antenna, The Cylindrical Antenna, The Biconical Antenna, The Loop Antenna, The Helical Antenna, Slot And Microstrip Antennas, Horn Antennas, Reflector Antennas, Lens Antennas, Leaky Wave And Surface-...
Circular Antenna Arrays Having Tangential Dipoles as Elements
The integral equations describing the current distribution along the elements of a circular array of tangential dipoles are formulated, and it is shown that the leading term of a series solution is the usual sinusoidal approximation. This approximate distribution is used to calculate the terminal sequence impedance and far-zone radiation patterns for arrays of half-wave dipoles. Patterns are also found for arrays of short dipoles. The effect of assymmetry in the interelement coupling is investigated, and it is shown that an odd component exists in the current distribution, but that is is negligible for half-wave dipoles. (Author).
Ultra-Wideband Phased Arrays
The report describes the activities and accomplishments associated with the two major technical tasks on this project. The first task is the development of a linearly polarized two-dimensional phased array which is well matched simultaneously over a large scan angle range and over an octave bandwidth. The second task is to extend the impedance matching of the linearly polarized element to an arbitrarily polarized element for wide-angle scanning and wide tunable bandwidth.
Study of Circular Arrays of Radial and Tangential Dipoles
The report contains the results of studies of an array of dipoles oriented tangential to a circle with the plane of the array parallel to an infinite lossless ground plane. In particular, an integral equation is obtained in which the unknown is the current distribution on the elements of the array. Also, an expression for the radiation patterns is determined and the theoretical pattern is compared to the experimental pattern for the zero voltage sequence connection. (Author).
Study of Circular Arrays of Radial and Tangential Dipoles
The circular arrays investigated consist of N identical center-fed cylindrical dipoles which lie in the plane of a circle and whose centers are equally spaced around the circumference of the circle. In the case designated 'tangential arrays' the elements are placed tangential to the circle and in the case designated 'radial arrays' they are placed radial to the circle. This study first presents the derivation of the integral equations defining the vector potential over the surfaces of the elements. These equations are reduced to a single integral equation by using sequence terminal voltages. The Gaussian quadrature formula for numerical integration is used to solve the equation for each sequence. Methods of obtaining the sequence terminal admittances are also described. Experimental results are compared with theory for a driven monopole in a tangential array positioned on a ground-plane. Radiation patterns determined from the numerical currents are compared with those obtained from assumed sinusoidal currents. (Author).
Electromagnetic Scattering by a Linearly Oscillating Target
A theoretical analysis is presented in this report which shows that when a plane electromagnetic wave is incident upon a perfectly conducting, linearly oscillating, arbitrarily shaped target, the scattered far field differs only in phase from the field scattered when the target is motionless. The explicit form of the phase modulation factor is derived to an accuracy of the order of v/c, where v and c are the velocities of target motion and electromagnetic waves respectively. Spectral analysis of the modulation shows that the power distribution varies with the shape of the motion, wavelength of the incident field, and magnitude of the projections of the oscillation in the incident and receiver directions. Power spectra are calculated for square, triangular, and sinusoidal periodic target motion as well as a superposition of two sinusoids of different frequency and amplitude. The results indicate that even small amplitude oscillations produce measurable modulations of the scatter field. (Author).
