Analysis of Dipole and Patch Antennas in Cylindrical Structures

Doctoral thesis, 1998

This thesis deals with the analysis of dipoles, patches, and aperture coupled patches located in an infinitely long cylindrical structure with arbitrary cross-section. The analysis exploits the two-dimensional nature of the structure by expanding all fields and currents in spatial harmonics along the cylinder axis, and solving the subsequent spectral two-dimensional problems by the moment method. The thesis work includes both development of methods and algorithms, implemented in Fortran programs, and analysis of antennas using the resulting computer codes. The contents of the different parts of the thesis is outlined below. A novel electric field integral equation (EFIE) is formulated for two-dimensional cylindrical structures. Three-dimensional sources are included by Fourier transformation along the cylinder axis. With the aid of a certain choice of basis functions, the EFIE is decoupled in terms of the transverse and longitudinal surface current components. Numerical results are compared to UTD calculations and measurements on dipole radiation. Self- and mutual impedances of dipoles in the presence of a perfectly conducting cylinder of arbitrary cross-section are calculated. The impedance calculation is split in one free space dipole-dipole coupling and one dipol-scatterer-dipole coupling. This makes a computationally efficient computer code possible. The code is validated by comparing to data from canonical cases. Asymmetric trough guide antennas are analyzed by the moment method. Phase constants and radiation patterns are calculated and compared to results calculated by other methods and measurements. A production trough guide antenna feeding a two-dimensional corrugated horn is analyzed and the numerical results are compared to measured data. Radiation from an aperture coupled patch element in a perfectly conducting (PEC) structure is analyzed. The analysis involves calculating the coupling from the slot to the patch in the presence of the PEC cylinder. Numerical results are compared to results calculated by other methods and measurements. Radiation patterns from patch antennas on finite width substrates are calculated and compared to results published in the literature. The element pattern of a base station antenna for mobile communication consisting of a four-element linear array of in-line fed patches covered by a radome is analyzed and the numerical results are compared to measured data.