Apm Peter Zwamborn

Design of Wire Antennas by Using an Evolved Particle Swarm Optimization Algorithm

A particle swarm optimization (PSO) algorithm has been used in conjunction with a full-wave numerical code based on the method of moments (MoM) to design and optimize wire antennas. The PSO is a robust stochastic evolutionary numerical technique that is very effective in optimizing multidimensional problems. The goal of the present work is to design wire antennas operating in a wide frequency range with a high gain level. A modified PSO algorithm will be presented in order to increase the efficiency in terms of convergence.

Experimental validation of the stochastic model of a randomly fluctuating transmission-line

A modeling method is proposed to quantify uncertainties affecting electromagnetic interactions. This method considers the uncertainties as random and measures them thanks to probability theory. A practical application is considered through the case of a transmission-line of varying geometry, illuminated by a fixed electromagnetic field. The results of the stochastic numerical model are compared to the measurements performed on the transmission-line setup.

Detection of a buried wire with two resistively loaded wire antennas

The use of two identical straight thin-wire antennas for the detection of a buried wire is analyzed with the aid of numerical calculations. The buried wire is located below an interface between two homogeneous half-spaces. The detection setup, which is formed by a transmitting and a receiving wire, is located above the interface. The transmitter is excited by a pulsed voltage in a small gap. A resistance profile according to Wu and King [1965] has been used to suppress the reflections at the end of the wires. This enhances the visibility of properties of the lower half-space directly from the time response of the current along the receiving antenna. The problem is solved in several steps. First, the electric field integral equation for the total current along a single thin-wire antenna in a homogeneous space is formulated. The result is then used to construct a set of coupled integral equations to describe the currents along all three wires without the resistive load. The integral equations contain the transmitted and reflected fields due to the interface. Next, the set of integral equations is adapted for the resistance profile along the wires of the detection setup. The reflected and transmitted fields in both half-spaces are treated as secondary incident fields in the integral equation for the currents along the wires. In these equations, the response from a pulsed dipole source in the same configuration occurs as a Greens function. The inverse spatial Fourier transformation that occurs in the transmitted and reflected fields is carried out with the aid of a frequency independent, composite Gaussian quadrature rule. The set of coupled integral equations is solved by using the continuous-time discretized-space approach, where the space discretization is kept fixed for all frequencies. This results in a linear system of equations with a fixed dimension which is solved by the conjugate gradient-fast Fourier transform (CG-FFT) method. With the aid of a marching-on-in-frequency scheme, the system is solved for a number of frequencies. Time domain results are obtained by applying an inverse Fourier transformation. Representative numerical results are presented and discussed.

DETECTION OF A BURIED OBJECT WITH PULSE-COMPENSATED WIRE ANTENNAS

For the detection of a buried object we consider two straight thin-wire antennas above an interface between two homogeneous dielectric half spaces. One antenna is a transmitting wire and the other is a receiving wire. Our aim is to use this simple antenna set up for the detection of buried objects without applying pre and post processing of the received signal. The buried wire can be detected directly from the shape of the current at the receiving antenna. To minimize the effects of repeated reflections at the end faces of the wire antennas, pulse compensation is introduced. Numerical results show that with the aid of pulse compensation a buried wire can easily be detected.