W. Rusch

Bio: W. Rusch is an academic researcher from Technical University of Denmark. The author has contributed to research in topics: Parabolic reflector & Phase (waves). The author has an hindex of 3, co-authored 3 publications receiving 53 citations.

The geometrical theory of diffraction for axially symmetric reflectors

Abstract: The geometrical theory of diffraction (GTD) (cf. [1], for example) may be applied advantageously to many axially symmetric reflector antenna geometries. The material in this communication presents analytical, computational, and experimental results for commonly encountered reflector geometries, both to illustrate the general principles and to present a compact summary of generally applicable formulas.

On numerical evaluation of two-dimensional phase integrals

Abstract: The relative advantages of several common numerical integration algorithms used in computing two-dimensional phase integrals are evaluated.

Dynamic measurement of forward scattering

Abstract: A dynamic method for the measurement of forward scattering in a radio anechoic chamber is described. The quantity determined is the induced-field-ratio (IFR) of conducting cylinders. The determination of the IFR is highly sensitive to 1) multiple scattering between the cylinder and the obpring antenna and 2) extraneous scattering from the lining of the anechoic chamber. In order to eliminate the influence of multiple scattering, the measurements are made dynamically, i.e., the cylinders are mounted on a moving cart. The consequences of this movement are analyzed. Experimental data are presented in terms of the dynamic measurements. The influence of extraneous scattering is evaluated and an indication of a method for reducing errors due to extraneous scattering is given.

Offset-parabolic-reflector antennas: A review

Abstract: Although used for some decades, the offset-parabolicreflector antenna's electrical properties and performance were not accurately modeled and optimized until the 1960's. This paper reviews, in a tutorial fashion, the state of the art of this important antenna for readers who are not necessarily experts in antenna theory and technology. After a discussion of fundamentals, the performances of both single- and double-reflector configurations are treated and compared, and practical primary feeds are described. Comments are given on the present status of analysis and design and on problems to be solved.

Millimeter-wave integrated-horn antennas. I. Theory

Abstract: The far-field pattern and input impedance of a dipole-fed horn antenna in a ground plane are calculated using full-wave analysis. The solution is based on the numerical evaluation of the pertinent Green's function for the horn structure and the application of the method of moments. The convergence characteristics of the full-wave analysis method are investigated, along the the resonant properties of the strip-dipole and the corresponding behavior of the far-field patterns. >

Diffraction by an arbitrary subreflector: GTD solution

Abstract: The high-frequency asymptotic solution of diffraction by a conducting subreflector is studied. By using Keller's geometrical theory of diffraction and the newly developed uniform asymptotic theory of diffraction, the scattered field is determined up to an including terms of order k^{-1/2} relative to the incident field. The key feature of the present work is that the surface of the subreflector is completely arbitrary. In fact, it is only necessary to specify the surface at a set of discrete points over a random net. Our computer program will fit those points by cubic spline functions and calculate the necessary geometrical parameters of the subreflector. In a companion paper by Y. Rahmat-Samii, R. Mittra, and V. Galindo-Israel, the scattered field from the submflector is used to calculate the secondary pattern of an arbitrarily shaped reflector by a series expansion method. Thus, in these two papers, it is hoped that we have developed a "universal" computer program that can analyze most dual-reflector antennas currently conceivable. It should also be added that our method of calculation is extremely numerically efficient. In many cases, it is one order of magnitude faster than the conventional integration method based on physical optics.

Comparison of Neural Networks for Resonant Frequency Computation of Electrically Thin and Thick Rectangular Microstrip Antennas

Abstract: Neural models for calculating the resonant frequency of electrically thin and thick rectangular microstrip antennas, based on the multilayered perceptrons and the radial basis function networks, are presented. Six learning algorithms, backpropagation, delta-bar-delta, extended-delta-bar-delta, quick-propagation, directed random search and genetic algorithms, are used to train the multilayered perceptrons. The radial basis function network is trained according to its learning strategy. The reason for using six different learning algorithms and two different structures is to speed up the training time and to compare the performance of neural models for this specific application. The resonant frequency results obtained by using neural models are in very good agreement with the experimental results available in the literature. When the performances of neural models are compared with each other, the best results for training and test were obtained from the radial basis function network

Rim loaded reflector antennas

Abstract: A general theory of reflector antennas loaded by surface impedances is presented. Spatial variation of primary illumination is taken into account using a generalized slope diffraction coefficient. The theory is experimentally checked on surface loaded square plate scatterers and then used for computing the radiation diagram of parabolic and hyperbolic dishes. Computer programs and computed diagrams refer to the case of focal illumination and negligible tapering of primary illumination.