Non-Foster radio frequency source

doctoral thesis

• Title (croatian): Nefosterovski radiofrekvencijski izvor
• Author: Aleksandar Kiričenko; MBZ: -333320
• 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: 2020, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Electrical Engineering
• Universal decimal classification (UDC): 621.3 - Electrical engineering

Abstract

This research focuses on broadband non-Foster matching of electrically small antennas, particularly in the transmitter applications. As a starting point, an effort was made to evaluate, theoretically and experimentally, the extent of advantages offered by non-Foster matching, if the stability problem (which is inherent for all non-Foster circuits) were not present. A linear, quadrature non-Foster-like circuit has been developed, which closely mimics the behaviour of non-Foster matched transmitter system, with the advantage that it does not suffer from stability issues. The behaviour of such a system is very similar to the behaviour of a native non-Foster matched transmitter, under the same conditions. The antenna reactance cancellation effect was confirmed experimentally and the radiated power was found to be constant within the wide frequency range. However, the efficiency of energy transfer to the antenna with this technique was found to be modest. Another, more versatile, linear non-Foster-like transmitter-antenna system was developed based on an RF current source that mimics open-circuit-stable non-Foster element behaviour. This principle of operation was verified through the measurements on a demonstrator and the results were consistent with theory and simulations. Both of the proposed linear non-Foster-like systems comprise linear amplifiers that generally exhibit low efficiency that is further deteriorated when driving highly reactive loads such as small antenna. Therefore, the solutions based on non-linear, discrete-time circuits were considered and investigated. Several non-linear non-Foster-like transmitter-antenna topologies were proposed, utilising voltage supply tracking, pulse width modulation and current tracking operation principles. The representative solution was practically verified by measurements on demonstrator model showing improvement of efficiency compared to linear non-Foster-like transmitter system, as well as further advantages over classic non-Foster matching.

Abstract (croatian)

Ovo istraživanje usredotočeno je na nefosterovsko prilagođenje električki kratkih antena posebno za odašiljačku primjenu. Kao polazište, pokušalo se teoretski i eksperimentalno utvrditi prednosti koje bi nudila tehnika nefosterovskog prilagođenja, u slučaju kada problem stabilnosti (koji je svojstven svim nenfosterovskim mrežama) ne bi bio prisutan. U tu svrhu razvijen je linearni kvadraturni sustav odašiljač-antena, koji vjerno oponaša funkciju klasičnog nefosterovski prilagođenog odašiljačkog sustava, s bitnom razlikom da ne sadrži pozitivnu povratnu vezu, koja je osnovni uzrok problema stabilnosti kod nefosterovskih elemenata. Ponašanje takvog sustava je vrlo slično ponašanju izvornog nefosterovskog odašiljačkog sustava. Simulacijama i eksperimentalno potvrđen je efekt poništenja reaktancije antene, što rezultira jednakom izračenjem snagom u širokom rasponu frekvencija. Međutim, učinkovitost prijenosa energije na antenu ovakvim sustavom ostaje i dalje skromna. Slijedeći, svestraniji linearni nefosterovski sustav odašiljač-antena razvijen je na temelju radiofrekvencijskog strujnog izvora koji oponaša nefosterovski element stabilan pri otvorenom kraju (OCS). Ispravnost ovog pristupa eksperimentalno je potvrđena, a rezultati su u skladu s teorijom i simulacijama. Oba predložena linearna sustava koji oponašaju nefosterovsko prilagođenje sadrže linearna pojačala koja su poznata kao nisko učinkovita, a što se dodatno pogoršava pri opterećenju vrlo reaktivnim trošilima, poput kratke antene. Stoga su razmatrana i istražena rješenja temeljena na nelinearnim sklopovima koji rade u diskretnom vremenu. Predloženo je i simulacijama evaluirano nekoliko nelinearnih rješenja sustava odašiljač-antena u sklopnom načinu rada: varijanta s adaptibilnim naponom napajanja, varijanta s pulsno-širinskom modulacijom i varijanta s praćenjem struje. Reprezentativno rješenje između predloženih praktično je verificirano mjerenjima na prototipu. Rezultati su pokazali poboljšanje učinkovitosti u usporedbi s linearnim, nefosterovski inspiriranim sustavom odašiljač-antena kao i nekoliko drugih prednosti u odnosu na klasično nefosterovsko prilagođenje.

• Keywords: small antenna; transmitter; non-Foster; reactance; power; matching; efficiency; non-linear; current tracking
• Keywords (croatian): kratka antena; nefosterovski; odašiljač; snaga; prilagođenje; efikasnost; linearno; nelinearno; sklopni; tranzistorska sklopka; pojačalo; praćenje struje; negativni pretvornik imitancije
• Language: english
• URN:NBN: urn:nbn:hr:168:019651
• 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=52325
• Type of resource: Text
• Extent: xvi, 173 str.
• File origin: Born digital
• Access conditions: Closed access
• Created on: 2022-03-09 13:54:16