Analysis and Optimization of Installed Antenna Performance

Time: Mon 2020-03-09 13.00

Location: Kollegiesalen, Brinellvägen 8, Stockholm (English)

Subject area: Electrical Engineering

Doctoral student: Henrik Frid , Skolan för elektroteknik och datavetenskap (EECS)

Opponent: Professor Hugh Griffiths, University College London

Supervisor: B. Lars G. Jonsson, Elektroteknisk teori och konstruktion

Abstract

This Ph.D. thesis consists of six papers, which are labeled with roman numerals. Papers I-III have already been presented in a licentiate thesis published in2017, and this Ph.D. thesis therefore focuses on Papers IV-VI. All six papersare within the scope of microwave and antenna engineering, with applications to radar, electronic warfare (EW), radio astronomy or communications.

The common theme for Papers IV-VI is installed antenna performance (IAP). These papers present three methods for solving three problems related to IAP, by using information available in the installed far-field data. In these papers, we address the main challenges within the scope of IAP, i.e. antenna placement, electromagnetic compatibility (EMC), estimation of installed system performance (particularly direction-of-arrival (DoA) estimation accuracy)and optimization methods to compensate for or minimize installation effects. The presented methods make no simplifying assumptions regarding the antennas or their installation, and instead rely on using the installed far-field data, which is obtained through computational electromagnetics. These methods are therefore valid for generic array antennas. The presented methods are useful for antenna placement studies, i.e. as input for the decision on antenna placement on a platform such as an aircraft, ship, satellite or car.

Paper IV considers the problem of antenna placement with respect to EMC. A platform, such as an aircraft, ship, satellite, or car, may have a large number of radio-frequency (RF) systems installed onboard. Since some systems transmit a high RF power, while other systems aim to receive weak RF signals, there is a significant risk for unwanted electromagnetic interference (EMI) due to an insufficient isolation between the antennas associated with each RF system. This paper presents a method for estimating the isolation between antennas installed on the same platform, in order to determine therisk for EMI as a function of antenna placement. Finally, a numerical case-study is presented, considering two monopole antennas installed on a small aircraft under line-of-sight conditions. Results are also presented for other installation configurations, where the antennas are not within line-of-sight.

Paper V considers antenna placement and radome design with respect to DoA estimation accuracy. Firstly, we define the term "installation error" applied to DoA estimation. A method for determining the DoA estimation accuracy for a specific installation is thereafter presented. The paper ends with a numerical case-study for an array antenna installed behind a single-shell radome in the tail of a realistic full-scale model of a fighter aircraft.

Paper VI presents a method to compensate for radome effects on radiation patterns for array antennas. A convex optimization approach is used to minimize the side-lobe level, while taking the radome effects and mutual coupling into account. The paper ends with a numerical case-study for amonopulse-array installed behind a single-shell radome.

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