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An Approximate Method for Calculating the Near-Field Mutual Coupling Between Line-of-Sight Antennas on Vehicles
KTH, School of Electrical Engineering (EES), Micro and Nanosystems.ORCID iD: 0000-0001-7812-9849
KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.ORCID iD: 0000-0001-7269-5241
2015 (English)In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 63, no 9, p. 4132-4138Article in journal (Refereed) Published
Abstract [en]

Calculating the mutual coupling between antennas on vehicles using full-wave simulations requires a vast amount of computer resources due to the electrical size of the structures. We therefore propose an alternative and approximate method to determine mutual coupling between antennas on vehicles for the case where there is line-of-sight (LOS) between the antennas. The proposed method is based on approximating the mutual coupling between LOS antennas on vehicles as near-field transmission between antennas in free space. We begin the analysis with a brief review of four methods for calculating the near-field free-space transmission. Of the investigated methods, we demonstrate that a nonsingular form of the near-field transmission integral originally proposed by Yaghjian (1982) is the most suitable for LOS antennas on vehicles. We introduce a modification to this method, in order to only use the antenna far-fields and geometrical separation to determine the mutual coupling. The comparison with full-wave simulations indicates that the proposed method has a good accuracy for LOS antennas. This paper ends with a full-scale mutual coupling calculation for two monopoles on an aircraft under LOS conditions, demonstrating a root mean square (rms) accuracy of 6 dB for frequencies up to 5 GHz, as compared with full-wave simulations.

Place, publisher, year, edition, pages
2015. Vol. 63, no 9, p. 4132-4138
Keywords [en]
Aircraft antennas, aircraft reliability, electrically large structures, electromagnetic interference, near-fields
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:kth:diva-173969DOI: 10.1109/TAP.2015.2447003ISI: 000360803400035Scopus ID: 2-s2.0-84940973948OAI: oai:DiVA.org:kth-173969DiVA, id: diva2:859216
Note

QC 20151006

Available from: 2015-10-06 Created: 2015-09-24 Last updated: 2022-06-23Bibliographically approved
In thesis
1. Analysis and Optimization of Installed Antenna Performance
Open this publication in new window or tab >>Analysis and Optimization of Installed Antenna Performance
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Analys och optimering av installerad antennprestanda
Abstract [en]

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.

Abstract [sv]

Denna doktorsavhandling består av sex forskningsartiklar, som här numreras med romerska siffror. Artiklarna I-III har redan presenterats i en licentiatavhandling som publicerades under 2017, och den här avhandlingen behandlar därför primärt Artiklarna IV-VI. Alla sex artiklar är inom mikrovåg- och antennteknik, med tillämpningar inom radar, telekrig (EW), radioastronomi och kommunikation.

Det gemensamma temat för Artiklarna IV-VI är installerad antennprestanda. Dessa artiklar presenterar tre metoder som har utvecklats för att lösa tre problem relaterade till installerad antennprestanda, genom att använda information som är tillgänglig i installerad fjärrfältsdata. I dessa artiklar bemöter vi de huvudsakliga utmaningarna inom installerad antennprestanda, dvs antennplacering, elektromagnetisk kompatibilitet (EMC) och telekonflikt, estimering av installerad systemprestanda (speciellt vinkelmätningsnoggrannhet), samt metoder för att kompensera för installationseffekter. Dessa metoder är inte baserade på några förenklande antaganden, och kan därför tillämpas för godtyckliga gruppantenner, där fjärrfältsdata bestäms med elektromagnetiska beräkningar (CEM). Metoderna är användbara exempelvis under en förstudiefas för en ny plattform (exempelvis ett flygplan, fartyg, satellit eller bil) för att fatta beslut om antennplaceringar.  

Artikel IV presenterar en metod för att uppskatta risken för telekonflikt för föreslagna antennplaceringar. En plattform har idag typiskt ett stort antal radiofrekvens (RF)-system ombord. Då vissa RF-system sänder en hög effekt, samtidigt som andra RF-system ska ta emot svaga signaler, finns det en risk för elektromagnetisk interferens (EMI), dvs telekonflikt, mellan dessa system. Telekonflikt kan alltså uppstå på grund av en för låg isolation mellan systemens antenner. Denna artikel presenterar en metod för att uppskatta isolationen mellan antennerna ombord som en funktion av deras placering. Flera antennplaceringar undersöks, inklusive monopolantenner installerade på ett litet flygplan, där antennerna har fri sikt till varandra. Resultat presenteras också för antenner som inte har fri sikt till varandra.

Artikel V handlar om antennplacering och radomdesign, med hänsyn till vinkelinmätningsnoggrannhet. Vi definierar först begreppet "installationsfel'' tillämpat på vinkelestimering. Därefter presenteras en metod för att uppskatta systemets vinkelinmätningsnoggrannhet för en föreslagen installation, genom att använda installerade fjärrfält som indata. Denna artikel presenterar en fallstudie för en liten gruppantenn med en radom, som installeras i aktern på ett modernt stridsflygplan.

Artikel VI presenterar en metod för att kompensera för radomers påverkan på strålningsdiagram hos gruppantenner. En konvex optimeringsmetod används för att minimera sidlobsnivån i en monopuls-gruppantenn, med hänsyn till de fel som radomen orsakar. Denna metod tar även hänsyn till övriga effekter, som till exempel ömsesidig koppling. Artikeln presenterar en  fallstudie för en liten gruppantenn som installerats bakom en enkelskalsradom.

Place, publisher, year, edition, pages
Kungliga Tekniska högskolan, 2020. p. 156
Series
TRITA-EECS-AVL ; 2020:15
National Category
Electrical Engineering, Electronic Engineering, Information Engineering Signal Processing
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-267562 (URN)978-91-7873-447-4 (ISBN)
Public defence
2020-03-09, Kollegiesalen, Brinellvägen 8, Stockholm, 13:00 (English)
Opponent
Supervisors
Funder
Vinnova, ChaseOn iAA
Note

QC 20200214

Available from: 2020-02-14 Created: 2020-02-13 Last updated: 2022-06-26Bibliographically approved

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Frid, HenrikJonsson, B. Lars G.

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