Title Modeliranje mikrotrakastih antena na sfernim strukturama Title (english) Modeling of microstrip antennas on spherical structures Author Nikša Burum Mentor Zvonimir Šipuš (mentor)Committee member Juraj Bartolić (predsjednik povjerenstva)Committee member Zvonimir Šipuš (član povjerenstva)Committee member Vesna Roje (član povjerenstva)Committee member Darko Žubrinić (član povjerenstva)Committee member Milan Bajić (član povjerenstva)Granter University of Zagreb Defense date and country 2004, Croatia Scientific / art field, TECHNICAL SCIENCES Universal decimal classificationUDC ) 621.3 - Electrical engineering Abstract Konformne antene definiraju se kao antene čiji je oblik prilagođen podlozi na koju su postavljene. Razlozi mogu biti aerodinamički, hidrodinamički, estetski ili dobivanje željenih zračećih svojstava. Zbog potencijalnih prednosti nad planarnim antenama konformne antene nalaze čitav niz primjena, kao npr. kod pametnih baznih stanica, na zrakoplovima, raketama, satelitima, itd. Nizovi konformnih antena mogu zakretati glavnu laticu bez opadanja dobitka antene dok potrebna fizička veličina ostaje gotovo jednaka kao kod planarnih nizova. Uz to sferni nizovi imaju mogućnost pomicanje jedne ili više glavnih latica preko cijele hemisfere te su stoga pogodni za praćenje satelita, u telemetriji itd. S druge strane, mikrotrakaste antene imaju čitav niz dobrih svojstava kao što su prilagodljivost oblika, mogućnost integriranja s elektroničkim sklopovima, niski profil, mala težina i cijena, te jednostavnost izrade. Stoga je postavljanjem mikrotrakastih antena na sfernu strukturu moguće jednostavno izvesti sferne antenske nizove. U ovom radu analizirani su sferni antenski nizovi. Kao antenski elementi razmatrane su pravokutne i kružne mikrotrakaste antene koje mogu biti ugrađene ili postavljene na općenitu višeslojnu sfernu strukturu. Metoda analize zasniva se na rješavanju integralne jednadžbe za električno polje numeričkim putem primjenom metode momenata. Analiza trodimenzionalne sferne strukture pojednostavljena je transformacijom problema u spektar jednodimenzionalnih problema. Pri tome je višeslojna sferna struktura rigorozno razmatrana uporabom odgovarajuće Greenove funkcije u spektralnoj domeni. Najveća mana spektralne metode leži u numeričkoj nestabilnosti koja se javlja kod analize struktura velikog radijusa. Numerička stabilnost postignuta je modifikacijom vektorske Legendreove transformacije i uvođenjem normaliziranih Legendreovih funkcija. Nadalje, kako bi se smanjilo potrebno vrijeme rada računala, razvijena je približna metoda izračuna koeficijenta sprege između elemenata antenskog niza. Uz to napravljena je usporedba sfernih i cilindričnih mikrotrakastih antena s ciljem da se naglasi važnost rigorozne analize mikrotrakastih antena na zakrivljenim strukturama te je razmatran utjecaj radijusa zakrivljenosti na ulaznu impedanciju, spregu i dijagram zračenja. Na osnovi razvijene spektralne metode analize izrađena je programska podrška koja računa ulaznu impedanciju, spregu između mikrotrakastih antena te dijagram zračenja sfernog antenskog niza. Izrađen je također eksperimentalni model na kojem je ispitana točnost razvijene programske podrške. U svim razmatranim slučajevima postignuto je dobro poklapanje između proračunatih i izmjerenih rezultata.
Abstract (english) Conformal antennas are defined as antennas that conform to the structure for other reason than electromagnetic. This reason can be aerodynamic, hydrodynamic, aesthetic, coverage reason or to obtain improved radiation properties. Because of these potential advantages over planar antennas conformal microstrip patch antennas have been proposed for a wide range of applications, eg. for smart base station, airborne radars, rockets, satellite tracking system, etc. The conformal arrays can scan the beam without drop of the gain, and the size of the conformal antenna needed for obtaining the same gain as its planar counterpart is approximately the same. Spherical arrays have possibility of directing single or multiple beams through complete hemisphere and, therefore, spherical arrays are an attractive solution for satellite tracking, telemetry, etc. On other hand, microstrip antennas have lot of good properties like possibility to conform to the structure, thin profile, light weight, low cost and simple manufacturing. Therefore, one possible and simple realization of a spherical array is to use patch elements on a spherical supporting structure. In the thesis we have studied the spherical arrays of rectangular and circular microstrip antennas embedded in or placed on a general multilayer spherical structure. The analysis approach is based on solving the integral equation for electric field by using the moment method. The solution procedure takes advantage of spectral-domain approach where the three-dimension problems is transformed into spectral of much simpler one-dimension problems. In the solution procedure the spherical multilayer structure is rigorously taken into account by calculating appropriate spectral-domain Green’s functions. The main disadvantage of spectral-domain method is numerical unstability appearing in the analysis of spherical structure with large radius. In order to avoid numerical problems a modified vector-Legendre transformation and normalized Legendre polynomials are defined and applied to the solution procedure. Furthermore, an approximate method is developed to calculate mutual coupling between arrays element with intention to decrease the needed computer calculation time. Moreover, the comparison of spherical and cylindrical patch antennas is given in order to show the importance of rigorous analysis of patch antennas on curved structures where both principal curvatures are different from zero. The influence of structure radius on input impedance, mutual coupling and radiation pattern was also investigated. We have made the program for calculating input impedance, mutual coupling and radiation pattern of spherical patch arrays based on developed spectral-domain approach. Furthermore, a laboratory model is built to test properties of different patch configurations and to validate accuracy of developed program. The calculated and measured values are in good agreement in all considered cases.
Keywords
mikrotrakaste antene
konformne antene
numeričke metode
metoda momenata
sprega između antenskih elemenata
spektralna metoda analize
antenski nizovi
sferni antenski nizovi
Keywords (english)
microstrip antennas
conformal antennas
numerical methods
moment method
antenna array mutual coupling
spectral analysys method
antenna arrays
spherical antenna arrays
Language croatian URN:NBN urn:nbn:hr:168:452702 Study programme Title: Doctoral study programme "Electrical Engineering and Computing" Type of resource Text Extent 153 str. ; 30 cm File origin Born digital Access conditions Closed access Terms of use Created on 2020-03-11 12:53:59
