Broadly tunable self-oscillating antenna based on negative immittance conversion

doctoral thesis

• Title (croatian): Širokopojasno ugodiva samooscilirajuća antena temeljena na negativnoj pretvorbi imitancije
• Author: Leo Vincelj
• Mentor: Silvio Hrabar (mentor)
• Committee member: Silvio Hrabar (član povjerenstva)
• Granter: University of Zagreb; Faculty of Electrical Engineering and Computing; (Department of Communication and Space Technologies); Zagreb
• Defense date and country: 2021, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Electrical Engineering
• Universal decimal classification (UDC): 621.3 - Electrical engineering

Abstract

The thesis deals with the investigation of the concept of a broadly tunable self-oscillating antenna (antenna-transmitter). Such an antenna is based on immittance conversion of a first electromagnetic (EM) radiator into its 'negative image'. This ‘negative image’ is further connected to a second, identical EM radiator, creating a frequency agile self-oscillating system. Expected application of such an antenna system is related to future self-oscillating reflective metasurfaces. The basic electronic circuit used in described self-oscillating antenna is a negative impedance converter (NIC). Therefore, NIC’s behaviour in the case of both ideal and realistic active elements, as well as EM radiators, is analysed both analytically and numerically. The analysis is focused on the influence of dispersion and non-linearity. Analytical models of NIC are derived in order to investigate the influence of non-idealities on the NIC input immittance. Analytical results were verified by measurements on the experimental demonstrators. Demonstrators comprise a NIC based on ultra-fast operational amplifiers, and crossed dipoles or elemental Huygens' EM radiators. Measurement results revealed the tuning range of 1:3 for the prototype with dipole-like antennas, and 1:2 for the prototype with Huygens' radiators. Finally, the implementations of various additional features such as injection locking and modulation, were discussed.

Abstract (croatian)

U radu je istražen koncept širokopojasno ugodive samooscilirajuće antene (antene-odašiljača). Takva antena temelji se na pretvorbi imitancije prvog elektromagnetskog (EM) radijatora u njegovu 'negativnu sliku'. Ta 'negativna slika' radijatora je zatim spojena na drugi identični EM radijator, stvarajući tako širokopojasno ugodivi samooscilatorni prilagođeni sustav. Očekivana primjena navedenog antenskog sustava je u budućim samooscilirajućim rekonfigurabilnim metapovršinama. Kako je osnovni sklop korišten u samooscilirajućoj anteni negativni pretvornik impedancije (NIC), analitički i numerički je istražen njegov rad u slučaju idealnih i realnih aktivnih elemenata, s posebnim naglaskom na utjecaj disperzije i nelinearnosti. U svrhu toga izveden je matematički model NIC-a i napravljena analiza utjecaja neidealnosti na ulaznu imitanciju. Također, napravljen je dizajn te su provedene numeričke simulacije elektromagnetskih radijatora korištenih u samooscilirajućem sustavu. Rezultati teorijske analize verificirani su mjerenjima na eksperimentalnim demonstratorima, odnosno prototipima. Demonstratori su temeljeni na negativnom pretvorniku impedancije sa ultra-brzim operacijskim pojačalima te ukrižanim dipolu sličnim antenama, odnosno Huygensovim elementarnim EM radijatorima. Ostvaren je raspon ugađanja frekvencije od 1:3 u slučaju dipolu sličnih antena te 1:2 u slučaju Huygensovih antena. Razmatrana je mogućnost modulacije i sinkronizacije samooscilirajuće antene vanjskim radiofrekvencijskim izvorom.

• Keywords: negative impedance converter; non-Foster networks; self-oscillating antenna; dispersion; non-linearity; Huygens’ radiator
• Keywords (croatian): negativni pretvornik impedancije; nefosterovske mreže; samooscilirajuća antena; disperzija; nelinearnost; Huygensova antena
• Language: english
• URN:NBN: urn:nbn:hr:168:094207
• Study programme: Title: Doctoral study programme "Electrical Engineering and Computing"; Study programme type: university; Study level: postgraduate; Academic / professional title: doktor/doktorica znanosti, po-dručje tehničkih znanosti (doktor/doktorica znanosti, po-dručje tehničkih znanosti)
• Catalog URL: http://lib.fer.hr/cgi-bin/koha/opac-detail.pl?biblionumber=52330
• Type of resource: Text
• Extent: x, 134 str.
• File origin: Born digital
• Access conditions: Open access
• Created on: 2022-03-09 14:56:41