Superluminal propagation in artificial electromagnetic structures.

doctoral thesis

• Title (croatian): Superluminalna propagacija u umjetnim elektromagnetskim strukturama.
• Author: Ivan Bonić; MBZ: -333336
• 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; Radio Communications
• Universal decimal classification (UDC): 621.3 - Electrical engineering

Abstract

This thesis is devoted to electromagnetic metamaterials (MTM), which are artificial structures with special electromagnetic properties that are not normally found in naturally occurring materials. Besides their unusual physical properties, some MTM-based electromagnetic structures can support superluminal propagation (propagation with velocities faster than the speed of light in vacuum c). Main goal is engineering of active superluminal structures and characterization of their electromagnetic properties. Superluminal propagation phenomena found in some passive MTMs are compared to the novel concept of active broadband non-Foster-based superluminal MTMs that support broadband phase or group velocity. A causal model of non-Foster-based epsilon-near-zero (ENZ) active MTM is developed and tested analytically and numerically. These active ENZ MTMs are ultra-wideband and support superluminal group velocity and superluminal phase velocity. In the end, the proposed theoretical approach is simulated and non-Foster negative capacitors in RF regime are designed, built and optimized. Furthermore, the proposed transmission-line-based non-Foster ENZ 1D MTM was built and tested in RF 2 MHz to over 40 MHz band. The experiments were conducted in both frequency and time domain, confirming the stable operation and the permittivity that is lower than the permittivity of vacuum (the ENZ behavior). The extractions further show that this medium has ultra-wideband EM characteristics that cannot be achieved with any existing passive MTMs. The post processing of extracted parameters revealed simultaneous superluminal phase velocity and superluminal group velocity within the bandwidth of more than four octaves. The superluminal behavior of the prototype was also demonstrated by measurements in time domain with the sinusoidal and Gaussian burst excitation signals. These measurements also revealed the superluminal behavior of pulses that are qualitatively very similar to previous “fast light” time-domain superluminal experiments in physics. The achieved theoretical and experimental results enable causal modeling of future stable 1D and 2D volumetric active non-Foster based MTMs that support ultra-wideband superluminal pulse propagation.

Abstract (croatian)

Ovaj doktorski rad je posvećen elektromagnetskim metamaterijalima (eng. MTM) koji su umjetne strukture sa specijalnim elektromagnetskim svojstvima koja ne nalazimo u prirodi. Uz njihova specijalna fizikalna svojstva, neke elektromagnetske strukture bazirane na metamaterijalima mogu podržavati superluminalnu propagaciju s brzinama većim od brzine svjetlosti u vakuumu c. Glavni cilj je dizajn i razvoj aktivnih superluminalnih struktura te karakterizacija njihovih elektromagnetskih svojstava. Fenomen superluminalne propagacije koji nalazimo u nekim pasivnim metamaterijalima je uspoređen s novim konceptom aktivnih širokopojasnih nefosterovskih superluminalnih metamaterijala koji podržavaju širokopojasnu faznu ili grupnu brzinu. Kauzalni model nefosterovskog aktivnog metamaterijala s permitivnosti blizu nule (eng. ENZ) je razvijen i testiran analitički i numerički. Ovi aktivni metamaterijali s permitivnosti blizu nule su ultraširokopojasni i podržavaju superluminalnu grupnu brzinu i superluminalnu faznu brzinu. Na kraju, predloženi teorijski pristup je simuliran te su razvijeni, napravljeni i optimizirani nefosterovski negativni kondenzatori u RF frekvencijskom području. Nadalje, predloženi nefosterovski 1D ENZ metamaterijal baziran na prijenosnim linijama je napravljen i testiran u RF području od 2 MHz do preko 40 MHz. Eksperimenti su napravljeni u frekvencijskoj i vremenskoj domeni te potvrđuju stabilan rad bez oscilacija te permitivnost koja je manja od permitivnosti u vakuumu (ENZ ponašanje). Ekstrakcije nadalje pokazuju da ovaj medij ima ultraširokopojasna elektromagnetska svojstva koja se ne mogu postići s pasivnim metamaterijalima. Postprocesiranjem ekstraktiranih parametara pokazana je istovremeno superluminalna fazna i superluminalna grupna brzina u frekvencijskom opsegu od preko četiri oktave. Superluminalno ponašanje ovog prototipa je također potvrđeno mjerenjima u vremenskoj domeni uz pomoć sinusnih i Gaussovih impulsnih pobudnih signala. Ova mjerenja također otkrivaju superluminalano ponašanje impulsa što je kvalitativno vrlo slično postojećim eksperimentima superluminalnog „brzog svjetla“ u fizici. Postignuti teorijski i eksperimentalni rezultati omogućuju kauzalno modeliranje budućih stabilnih 1D i 2D volumetrijskih aktivnih nefosterovskih metamaterijala koji podržavaju ultraširokopojasnu superluminalnu propagaciju impulsa.

• Keywords: RF; ENZ; active metamaterial; superluminal propagation; superluminal group velocity; causality; non-Foster; Lorentz dispersion; active medium
• Keywords (croatian): radio frekvencijski; permitivnost blizu nule; aktivni metamaterijal; superluminalna propagacija; superluminalna grupna brzina; kauzalnost; nefosterovski; Lorentz disperzija; aktivni medij
• Language: english
• URN:NBN: urn:nbn:hr:168:222263
• Promotion: 2020
• 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)
• Type of resource: Text
• Extent: 370 str.
• File origin: Born digital
• Access conditions: Closed access
• Created on: 2020-09-14 14:40:53