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Izvedba kakovostnega spektralnega analizatorja s sledilnim izvorom, ki kot rezultat meritve podaja natančen oris razmer na njegovem vhodu, ostaja nespremenjena že zadnjih 50 let. Napredki pri izdelavi polprevodnikov in integriranih vezji omogočajo kompaktnejšo vgradnjo, kompleksnejšo obdelavo in nižjo ceno končne naprave. Najnovejša tehnologija sicer odpira pot povsem digitalni obdelavi visokofrekvenčnega signala, a najprestižnejši instrumenti uglednih proizvajalcev še vedno posegajo po precej dražji in razvojno kompleksnejši analogni različici, idejno enaki tisti izpred pol stoletja. Rezultatu povsem analogne obdelave signala lahko z gotovostjo zaupamo, saj do napak pride kvečjemu zaradi naše nepravilne uporabe (prevelika vhodna moč signala, neustrezno napajanje analognega vezja). Obdelavo opravlja kopica namenskih vezji, ki merjeni signal ustrezno preoblikuje in obdela. Še najbolj se zatakne pri izdelavi zelo ozkih frekvenčnih sit za doseganje boljše selektivnosti, saj so ta precej lažje izvedljiva v digitalni domeni, kar premami tudi resnejše proizvajalce. Žal so digitalne izvedbe pogosto izvor zahrbtnih napak, ki proizvedejo neverodostojen rezultat meritve, te pa je zelo težko odkriti, še težje popraviti, saj je programska oprema instrumentov zaščitena z vrsto šifrirnih mehanizmov. Večina sodobnih spektralnih analizatorjev s sledilnim izvorom glavnini inženirjev še vedno ni dosegljiva, težko si jo privoščijo že najimenitnejše raziskovalne inštitucije. Proizvajalci so k nižanju cen merilnih naprav pristopili z zamenjavo najdražjih namenskih delov za cenejše široko-potrošne gradnike, predvsem pa s preskokom v digitalno domeno zelo zgodaj v analogni verigi obdelave, ter izvedbo vseh pasovno nastavljivih sit v namenskih DSP rutinah. Sicer znatna pocenitev inštrumenta prinese svoje omejitve. Analogno-digitalni pretvornik je omejen z dinamičnim območjem, njegova frekvenca vzorčenja pa določa najširše sito, ki narekuje najvišjo hitrost frekvenčnega preleta. Meritev prenosne funkcije sit z visoko kvaliteto ali opazovanje hitrih signalov avionike je s takšnimi napravami skoraj nemogoče opravilo. To delo predstavlja inovativen pristop k načrtovanju in izgradnji spektralnega analizatorja s sledilnim izvorom za območje med 100 kHz in 4 GHz, s povsem analogno obdelavo signala, brez uporabe dragih namenskih gradnikov in s postopki izdelave, ki so lahko ponovljivi v domači delavnici. Zaradi načina zasnove je končna cena izdelka precej nižja od profesionalnih inačic, ključni gradniki, ki jih z neprimernim rokovanjem lahko uničimo, pa so enostavno zamenljivi. Spektralni analizator deluje kot sprejemnik z večkratnim mešanjem vhodnega signala na različne medfrekvence, pri čemer lokalni oscilator prvega mešalnika opravlja frekvenčni prelet, vsi ostali oscilatorji pa se nahajajo na konstantnih frekvencah. Disertacija predstavlja način izvedbe širokopasovnega frekvenčnega preleta med 4,3 GHz in 8,3 GHz z uporabo več ozkopasovnih oscilatorjev in preklapljanjem med njimi. S tem zagotavlja kakovosten signal prvega lokalnega oscilatorja z nizkim faznim šumom brez neželenih produktov delovanja ulomkove fazno sklenjene zanke. Moteč upad izhodne moči z višanjem frekvence odpravi z inovativno uporabo fotovolatičnega modula za ustvarjanje prednapetosti vrat namenskega nizko-šumnega ojačevalnika s pozitivnim naklonom ojačanja. Vsa medfrekvenčna sita tega dela so izvedena analogno. Votlinsko sito na prvi medfrekvenci 4,3 GHz iz široko-dostopnih aluminijastih profilov, LC sita na nižjih frekvencah pa s spreminjanjem kvalitete resonančnega vezja in s tem elektronsko izbiro pasovne širine med 3 MHz in 30 kHz. Še ožje sito je načrtovano z uporabo piezoelektričnih resonatorjev za 10 MHz, kar omogoča izvedbo najožjega področja vse do 1 kHz. Sledilni izvor poleg želenega izhodnega visokofrekvenčnega signala vključuje tudi podvojeno strukturo mešalnikov in lokalnih oscilatorjev, ki zagotavljajo referenčni signal faznemu detektorju, s tem pa razširitev nabora različnih meritev končne naprave. Tudi ta obdelava je izvedena povsem analogno, kar omogoča neodvisno spreminjanje frekvenc vseh lokalnih oscilatorjev in ohranjanje podatkov umerjanja v primeru izgube napajanja. S koraki analogne obdelave signala je mogoče neodvisno upravljati preko preprostih znakovnih ukazov, ki jih razume programska oprema mikrokrmilnika. Opis vseh sestavnih blokov je natančno razčlenjen, z navedbo zahtev in omejitev načrtovanja. Prikazane so podrobne električne sheme vseh vezji in ključne meritve parametrov, ki krojijo končne zmogljivosti instrumenta. Poseben poudarek je namenjen faznemu šumu prvega lokalnega oscilatorja, ki omejuje uporabnost najožjih pasovnih sit v medfrekvenčni obdelavi signala. Ustvarjanje frekvenčnega preleta je izvedeno z zaporedno vezavo dveh fazno sklenjenih zank s pripadajočimi nizko-šumnimi ozkopasovnimi oscilatorji, pri čemer v ulomkovem načinu deluje prvi oscilator verige, njegov izhod pa je uporabljen za takt celoštevilskega načina faznega detektorja drugega oscilatorja. Z izbiro integriranega vezja STuW81300 je na njegovem mestu na voljo 128 ozkopasovnih oscilatorjev, med katerimi preklaplja ustrezna programska koda izbranega mikrokrmilnika. Vzrok popačenja merjenega signala bo v največji meri odvisen od izbire prvega mešalnika analogne verige. Uporaba komercialno dostopnega gradnika na mestu mešalnika se zaradi nizke cene in enostavne vgradnje potrdi kot smiselna izbira. Ker gre za občutljiv gradnik, ki omejuje vhodno moč instrumenta, so podane natančne meritve presečne točke intermodulacijskega popačenja tretjega reda in točke zasičenja za celotno načrtovano frekvenčno področje. Nadalje je predstavljena nova izvedba pasovnoprepustnega sita z elektronsko izbiro njegove širine. Nadzorovanje kvalitete LC resonatorja, s tem pa širine prepustnega pasu, je izvedeno s PIN diodami, pri čimer je spreminjanje kapacitivnosti diode med preklopom zadosti majhno, da ne povzroči premika osrednje frekvence nihajnega kroga. Uglaševanje takšnega vezja je precej enostavnejše od izvedb v industrijskih inačicah, kar poenostavlja rokovanje s končnim instrumentom in ne zahteva dodatnega umerjanja med samim delovanjem naprave. Digitalno vzorčenje analognega signala po končni obdelavi vrši mikrokrmilnik STM32G441, ki hkrati izvaja zahtevane korake nastavljanja fazno sklenjenih zank vseh lokalnih oscilatorjev. Podatke o amplitudi in fazi merjenega signala v agregirani obliki posreduje uporabniškemu vmesniku, ki jih prikaže na interaktivnem zaslonu na dotik. Predstavljen instrument tako ostaja zvest zaupanja vredni analogni zasnovi, uporabi sodobnih nizkocenovnih gradnikov za proizvajanje signala lokalnih oscilatorjev in razširi nabor meritev s sledilnim izvorom z vpeljavo vektorskega načina merjenja. The implementation of a spectrum analyzer with a tracking generator, which as a result of the measurement gives an accurate representation of the conditions at its input, has remained mostly unchanged for the past 50 years. Advances in the manufacture of semiconductors and integrated circuits allow for more compact installation, complex processing, and a lower price of the final device. The latest technology paves the way for completely digital signal processing, but the most prestigious instruments from reputable manufacturers still resort to a much more expensive and developmentally more complex analog version, conceptually identical to those from half a century ago. We can trust the result of completely analog signal processing with certainty, since errors occur mostly due to our improper use (excessive input power, inadequate power level of the analog circuit). The processing is performed by many dedicated circuits, which appropriately transform and process the measured signal. The problem arises while making very narrow frequency filters to achieve better selectivity, as these are much easier to implement in the digital domain, so much so that it tempts even more serious manufacturers. Unfortunately, digital implementations are often the source of insidious errors that produce an unreliable measurement result, which are very difficult to detect and even more difficult to correct, since the instrument software is protected by heavy encryption mechanisms. Most modern spectrum analyzers with a tracking generator are still beyond the reach of the majority of engineers, as even the finest research institutions can hardly afford them. Manufacturers approached the reduction of the price of measuring devices by replacing the most expensive dedicated parts for cheaper widely used building blocks, and above all by switching to the digital domain very early in the analog signal path (implementing all band-pass filters in dedicated DSP routines). This significant cheapening of the instrument brings its limitations. An analog-to-digital converter is limited by its dynamic range and its sampling frequency defines the widest filter range that dictates the highest rate of frequency sweep. Measuring the transfer function of high-quality filters or observing fast avionics signals is almost impossible with such devices. This work presents an innovative approach to the design and construction of a spectrum analyzer with tracking generator, working between 100 kHz and 4 GHz, and fully analog signal processing, without the use of expensive dedicated building blocks, and with manufacturing processes that can be replicated in the home workshop. Due to the way of design, the final price of the product is much lower than the professional versions, and the key components, which can be destroyed by improper handling, are easily replaceable. The spectrum analyzer acts as a receiver by repeatedly mixing the input signal to different intermediate frequencies, whereby the local oscillator of the first mixer performs a frequency sweep, while all other oscillators are set to constant frequencies. The dissertation presents a novel method of performing wide-band frequency sweep between 4.3 GHz and 8.3 GHz using several narrow-band oscillators and switching between them. It thereby provides a high-quality signal for the first local oscillator with low phase noise and without unwanted products of fractional phase-locked loop operation. The drop in output power with increasing frequency is eliminated by the innovative use of a photovoltaic module to bias the gate of a dedicated low-noise amplifier. All filters are made analog. Cavity filter at the first intermediate frequency of 4.3 GHz is constructed with wide-access aluminium profiles, and LC filter at lower frequencies by changing the quality of the resonant circuit and thus electronically selecting the bandwidth between 3 MHz and 30 kHz. An even narrower filter is designed using piezoelectric resonators, which enables the implementation of the narrowest bandwidth down to 1 kHz. In addition to the desired high-frequency output signal, the tracking generator also includes a duplicate structure of mixers and local oscillators that provide a reference signal to the phase detector, thereby expanding the range of various measurements of the end device. This processing is also completely analog, which allows for independent changing of the frequencies of all local oscillators and preservation of calibration data in case of power loss. Signal path can be independently controlled via simple character commands understood by the microcontroller software. All building blocks are thoroughly described, together with all of the requirements and constraints. Detailed electrical diagrams of all circuits and key parameter measurements that shape the instrument's end capabilities are shown. Special emphasis is given to the phase noise of the first local oscillator, which limits the usefulness of the narrowest bandpass filters. The generation of the frequency sweep is performed by sequentially connecting two phase-locked loops with the corresponding low-noise narrowband oscillators, whereby the first oscillator of the chain operates in fractional mode, and its output is used to clock the phase detector of the second oscillator in integer mode. By choosing the STuW81300 integrated circuit, 128 narrowband oscillators, managed by a microcontroller, are available. The choice of the first mixer in the analog chain will have a significant impact on the measured signal's distortion. The use of a commercially available building block in place of the mixer proves to be sensible due to its low cost and easy installation. Because it is a sensitive component that limits the input power of the instrument, accurate measurements of the third-order intermodulation distortion intersection and saturation points are given for the entire frequency range. Furthermore, a new version of the bandpass filter with electronic selection of its width is presented. Controlling the quality of the LC resonator, and thus the width of the passband, is performed via PIN diodes, whereby the change in diode capacitance during switching is small enough to not cause a shift in the central frequency of the oscillating circuit. Tuning is much simpler than in case of the industrial equivalents, which simplifies the handling of the instrument and does not require additional calibration during the operation of the device itself. Digital sampling of the analog signal after final processing is performed by the STM32G441 microcontroller, which simultaneously performs the required steps in setting the phase-locked loops of all local oscillators. It sends aggregated data of the detected signal's amplitude and phase to the user interface, which are shown on an interactive touch screen. The presented instrument stays true to the proven analog design, employs modern, reasonably priced building blocks for the generation of local oscillator signals, and increases the scope of tracking generator measurements by adding a vector measurement mode.

V doktorski disertaciji je predstavljena izvedba vključitve optoelektronskega oscilatorja (angl. opto-electronic oscillator – OEO) v radijsko dostopno omrežje (angl. radio access network – RAN). OEO je odlična rešitev za proizvajanje signala z nizkim faznim šumom v mikrovalovnem in milimetrskem valovnem področju. Za poenostavitev trenutne zgradbe baznih postaj v radijskem dostopovnem omrežju je predlagana izvedba enozančnega OEO. Poenostavitev je zagotovljena s tem, da ni potrebe po lokalnih oscilatorjih (angl. local oscillator – LO) v baznih postajah zahvaljujoč razdelitvi oscilatorjevega signala, ki ga oddaja centralni OEO. To je doseženo z uporabo enozančnega OEO v centralni postaji radijskega dostopovnega omrežja in distribucijo signala iz optoelektronskega oscilatorja na bazne postaje preko optičnega razdelilnega omrežja imenovanega pasivno optično omrežje (angl. passive optical network – PON). Kot prvi korak tega dela je pojasnjena preliminarna ideja za vključitev enozančnega OEO v radijsko dostopovno omrežje. Pojasnjena je splošna ideja in način razdeljevanja signala optoelektronskega oscilatorja od centralne postaje do več baznih postaj. Poleg tega se preučujejo možni izzivi predlagane ideje. Izvede se pregled literature in ponudijo se možne rešitve za premagovanje potencialnih izzivov pri vključevanju. Eden glavnih izzivov je izguba moči zaradi barvne disperzije pri razdelitvi visokofrekvenčnega signala. Izguba moči lahko resno poslabša razdelitev signala optoelektronskega oscilatorja na nekatere bazne postaje preko pasivnega optičnega omrežja, ker je v mikrovalovnem in milimetrskem valovnem področju barvna disperzija na valovni dolžini 1550 nm zelo prevladujoča. Barvna disperzija povzroči fazni premik in izgubo moči na razdeljujočem optičnem signalu. Kot rešitev je v tej disertaciji predlagana uvedba nastavljivega modula za kompenzacijo disperzije (angl. tunable-dispersion compensation module – TDCM) za vsako bazno postajo, ki kompenzira barvno disperzijo. Optoelektronski oscilator v kombinaciji z nastavljivimi moduli za kompenzacijo barvne disperzije preprečuje izgubo moči. S to sistemsko konfiguracijo je dosežena razdelitev signala pri valovni dolžini 1550 nm za frekvence od 10 MHz do 45 GHz. Večrodovno delovanje je dodaten izziv pri uvedbi enozančnega optoelektronskega oscilatorja v radijsko dostopovno omrežje. Večrodovno delovanje optoelektronskega oscilatorja je posledica neidealnega filtriranja električnega pasovno propustnega sita (angl. bandpass filter - BPF). Nezaželeni dodatni rodovi optoelektronskega oscilatorja so filtrirani, vendar niso v celoti odstranjeni zaradi neustrezne pasovne širine električnega sita. Zaradi fizikalnih omejitev, izdelava električnega pasovno propustnega sita z zelo ozko pasovno širino, ni preprosta inženirska naloga. Uvedena je kaskadna povezava dveh neidealnih električnih sit. Eno od njih ima premaknjeno glavno frekvenco v levo, medtem ko ima drugo glavno frekvenco premaknjeno v desno od želene centralne frekvence. Ti kaskadni električni siti sta vključeni v enozančni optoelektronski oscilator. S to idejo se razmerje oslabitve stranskega rodu (angl. side-mode suppression ratio – SMSR) izboljša za 8,3 dB. Ta pristop je koristen za povečanje učinkovitosti uvedbe enozančnega optoelektronskega oscilatorja v radijsko dostopovno omrežje. Ta disertacija predstavlja tudi nov učinkovit pristop za merjenje prostega spektralnega področja (angl. free spectral range – FSR) in SMSR pri enozančnem OEO za različne dolžine optičnih vlaken. Inovativna izvedba obsega kombiniranje avtomatskega izbirnika poti iz optičnih vlaken z enozančnim optoelektronskim oscilatorjem. S tem merilnim pristopom je mogoče določiti optimalno dolžino optičnih vlaken enozančnega OEO glede na SMSR in FSR električnega pasovno propustnega sita. Ta merilni pristop je uporaben za preizkušanje, karakterizacijo ali preiskovanje različnih vrst električnih pasovno propustnih sit, da bi zagotovili najboljše delovanje v konfiguracijah eneozančnega OEO. V naslednjem poglavju disertacije se meri poslabšanje faznega šuma za signal iz optoelektronskega oscilatorja, kjer se mikrovalovni signal razdeli v bazne postaje preko optičnega razdelilnega omrežja imenovanega pasivno optično omrežje. Signal iz enozančnega OEO, ki deluje pri 10,5 GHz, se preko pasivnega optičnega omrežja razdeli baznim postajam. Z analizatorjem signalnega izvora (angl. signal source analyser – SSA) je izvedena meritev faznega šuma na izhodu enozančnega OEO in pri bazni postaji. Z avtomatskim izbirnikom poti optičnih vlaken se položaj bazne postaje spreminja od 5 km na 35 km s korakom po 5 km. Fazni šum se za optične razdalje do 20 km poslabša za manj kot 2 dB. Takšno poslabšanje faznega šuma je praktično zanemarljivo, kar podpira glavno hipotezo disertacije, da je v radijskem dotopovnem omrežju naslednje generacije mogoče uvesti centraliziran optoelektronski oscilator. In this PhD dissertation, an opto-electronic oscillator (OEO) implementation for a radio access network (RAN) is introduced. The OEO is an excellent solution for producing a low phase noise signal in the microwave and millimetre wave ranges. The implementation of a single-loop OEO in the RAN is proposed in order to simplify the current configuration of the base stations in the RAN. Simplification is assured due to the fact that there is no need for local oscillators in the base station thanks to the oscillator signal distributed from the centralized OEO. This is achieved by employing the single-loop OEO in the central station of the RAN and distributing the OEO’s signal to base stations via an optical distribution network called passive optical network (PON). As the first step of this work, the preliminary idea for the single-loop OEO implementation in the RAN is clarified. The general idea and the way in which the OEO signal is distributed from a central station to multiple base stations are explained. In addition, the possible challenges of the proposed idea are investigated. A literature review is performed and possible solutions are offered to overcome the potential challenges of the implementation. One of the main challenges is the power penalty due to chromatic dispersion for high-frequency signal distribution. The power penalty can seriously degrade the OEO’s signal distribution to some base stations via PONs because chromatic dispersion in the 1550-nm wavelength is very dominant in the microwave and millimetre wave ranges. Chromatic dispersion causes a phase shift and power loss for the distributed optical signal. As a solution in this dissertation implementation of a tunable-dispersion compensation module (TDCM) for each base station to tune for compensation of the chromatic dispersion is proposed. The OEO is combined with the TDCMs to compensate the chromatic dispersion and to avoid the power penalty. With that system configuration, the penalty-free distribution of signal in the 1550-nm wavelength for the frequencies from 10 MHz to 45 GHz is achieved. Multi-mode operation is another challenge of single-loop OEO implementation in the RAN. The multi-mode operation of the OEO is a result of the non-ideal filtering of the electrical bandpass filter (BPF). Undesired OEO’s spurious modes are filtered but are not totally removed because of bandwidth insufficiency of the electrical BPF. Manufacturing very narrow-bandwidth electrical BPF is not an easy engineering task because of physical limitations. A cascaded connection of the two non-ideal electrical filters is introduced. One of cascaded filters has a shifted main frequency to left while other has shifted main frequency to the right of wanted central frequency. Those cascaded electrical BPFs are implemented in the single-loop OEO. With that idea, the side-mode suppression ratio (SMSR) is improved by 8.3 dB. This approach is useful for increasing the efficiency of single-loop OEO implementation in RANs. This dissertation also presents a novel efficient approach to measure the free spectral range (FSR) and SMSR of the single-loop OEO for various optical fibre lengths. The innovative approach comprises the combination of an automated optical fibre path selector with a single-loop OEO. With this measuring approach, the optimum optical fibre length of the single-loop OEO can be selected regarding the SMSR and FSR of the electrical BPF. This measuring approach is useful for testing, characterizing, or investigating different kinds of electrical BPFs to provide the best performance in single-loop OEO configurations. In a subsequent chapter of the dissertation, the phase-noise degradation of the OEO signal is measured where the microwave signal is distributed to the base stations via an optical distribution network called a PON. The single-loop OEO is operating at 10.5 GHz and the produced signal is distributed to base stations via PONs. The phase noise measurement is made by a signal source analyser at the output of the single-loop OEO and at the base station. The base station position is changed from 5 km to 35 km with 5-km increments using the automated optical fibre path selector. The phase noise is degraded by less than 2 dB for optical distances up to 20 km. Thus, the phase noise degradation is practically negligible and this supports the main hypothesis of the dissertation proposal for centralized OEO implementation in the next-generation RAN.

Z izgradnjo novih sinhrotronskih pospeševalnikov četrte generacije se gradijo tudi potrebe po čedalje bolj natančni sinhronizaciji krmiljenja pospeševalnih enot. Za zagotavljanje teh je potrebna časovna sinhronizacija celotne dolžine pospeševalnika z napako, ki pogosto ne sme presegati časa nekaj deset femtosekund. Diplomsko delo predstavlja razvoj novega referenčnega oscilatorja, ki nadgrajuje funkcionalnost obstoječega sistema. Zasnova novega instrumenta temelji na uporabi temperaturno stabiliziranega kristalnega oscilatorja in tehnologiji direktne digitalne sinteze signalov. Z odpravljenimi problemi proizvodnje, dodanimi novimi funkcijami in primerljivim faznim šumom lahko novi instrument konkurira izdelkom vodilnih proizvajalcev v industriji. Potencialno lahko služi tudi kot osnova za razvoj produkta, ki bi bil primeren za prodajo na širšem trgu. With the construction of new fourth-generation synchrotron accelerators the need for increasingly precise beam control and regulation systems is also being built. In order for those to work the entire length of the accelerator has to be synchronised with a timing error often as low as only a few tens of femtoseconds. The thesis describes the development of a new reference oscillator with a goal of extending the functionality of the previous system. The design of the new instrument is based on the use of an oven controlled crystal oscillator and direct digital synthesis to generate required signals. With the production issues fixed and new features added the instrument has also been able to retain good performance. This puts it on par with products from industry's leading manufacturers. The instrument could serve as a basis for further development of products more suited for a wider market.

Delo naslavlja merjenje faznega šuma elektronskega oscilatorja s pomočjo optoelektronskih merilnih pristopov. V prvem delu je predstavljena formulacija spektralnih veličin za opis šuma. Sledi izpeljava Leesonove enačbe faznega šuma, ki oscilator obravnava kot linearni časovno invariantni sistem. Naslednje poglavje je namenjeno pregledu metod za merjenje faznega šuma. Kratko so opisane direktna metoda, metoda faznega detektorja in metoda dvokanalne križne korelacije. Metodi frekvenčnega diskriminatorja je posvečeno svoje poglavje, v katerem je predstavljena prenosna funkcija splošnega frekvenčnega diskriminatorja. Obravnavane so različne realizacije kasnilnega elementa. Postopoma je sestavljen sistem frekvenčnega diskriminatorja z optično kasnilno linijo. V drugem delu so predstavljene izdelane komponente merilnega sistema, ki zajemajo optični sprejemnik, ojačevalnike, sita in mešalnike. Sledi postavitev merilnega sistema, opis umerjanja in izvedba meritve faznega šuma. Meritev je izvedena na treh izvorih signala pri frekvenci 10,5 GHz. Dobljeni rezultati so ponovljivi za različne postavitve sistema in se ujemajo z meritvijo faznega šuma po direktni metodi. Na koncu so predstavljene možne izboljšave sistema. This study was a phase-noise measurement of an electronic oscillator employing optoelectronic measuring approaches. In the first part, a formulation of tne spectral quantities of the noise are presented. A derivation of Leeson's equation for phase noise follows, where the oscillator is treated as a linear time-invariant system. The next section is dedicated to an overview of the methods for phase-noise measurements. The direct method, the phase-detector method and dual-channel cross-correlation method are briefly described. A separate section is dedicated to the frequency-discriminator method in which the transfer function of a generic frequency discriminator is presented. Different implementations of the delay element are treated. A frequency discriminator with an optical delay line is gradually developed. In the second part, fabricated components of the measuring system are presented. These include an optical receiver, amplifiers, filters and mixers. A presentation of the measuring system follows,with a description of the calibration and the measurement of phase noise. The measurement is performed on three different signal sources at a frequency 10.5 GHz. The obtained results are reproducible for different variations of the measurement setup and they agree with the results obtained using the direct method. Finally, a few potential improvements to the setup are presented.

Delo se ukvarja z vrednotenjem faznega šuma ulomkove fazno sklenjene zanke. Z opisom teoretičnega ozadja delovanja PLL zanke tako v celoštevilskem kot ulomkovem načinu preide v opis posameznih gradnikov skupaj s tehnološkimi omejitvami in primeri izvedbe. Fazni šum je opisan iz primera vrste šuma, tako matematično kot vizualno, v primeru vklenjene zanke. Praktični del predstavlja gradnjo frekvenčnega izvora s pomočjo integriranega čipa MAX2871, dodana so tudi navodila, kako prototip sestavimo v domači delavnici s pomočjo široko dostopnih orodji. Predstavljeni so podporni sistemi za komunikacijo s PLL čipom preko USB povezave, ter metoda za samodejno merjenje faznega šuma s pomočjo programskega jezika Python, ter spektralnega analizatorja. Meritve prikazujejo vpliv različnih načinov delovanja na spreminjanje faznega šuma. Izmerjen je vpliv toka črpalke naboja, stopnja linearnosti, ter različni režimi za izločanje neželenih špičk. Predstavljena je tudi samodejna meritev faznega šuma v celotnem frekvenčnem področju. V zaključnem delu je predstavljena izvedba fazno sklenjene zanke s FPGA, ki je bila sicer uspešna, a s stališča faznega šuma zaradi presluha v notranjosti čipa slaba. The work deals with the evaluation of the phase noise in the fractional phase locked loop. The theoretical background of the PLL loop in both integer and fractional mode is presented. Description of each component along with the techical limitations and examples is added. Phase noise is described both mathematically and visually in the case of the locked loop system. The practical part presents the construction of the frequency source by means of the integrated chip MAX2871. Instructions on how to assemble a prototype in the home workshop by using widely available tools are also added. Support systems to communicate with PLL chip via a USB connection, and a method for automatically measuring the phase noise by using the programming language Python and the spectrum analyzer are described at the end of the chapter. Phase noise measurements of MAX2871 were performed at different modes in acton, changes in the charge pump current, degree of linearity and modes for reducing unwanted spurs. Automatic method of complete spectrum measurment is also presented. In the final part, implementation of phase locked loop with FPGA is described, which although has been successful, was from the standpoint of phase noise bad due to crosstalk inside the chip.

Mikrovalovni oscilatorji so danes nepogrešljiv del merilne tehnike in komunikacijskih sistemov. Med seboj se ločijo po lastnostih, kot so dolgoročna stabilnost, območje frekvenčnega uglaševanja in fazni šum. Pogosto se te tri lastnosti medsebojno izključujejo. Sistemi za merjenje časa tako na primer zahtevajo izjemno točnost frekvence. Frekvenca takega oscilatorja je fiksna in se med delovanjem ne sme spreminjati. Dolgoročna stabilnost je v tem primeru zelo dobra, nizkega faznega šuma pa ni mogoče doseči brez dodatnih nizkošumnih oscilatorjev. Lokalni oscilatorji so pogosto napetostno krmiljeni. V tem primeru je pomembno, da je oscilatorju mogoče spreminjati frekvenco v določenem območju. Nizek fazni šum je zaželen, vendar pa ni izvedljiv zaradi slabših lastnosti resonatorjev (v primerjavi z oscilatorji s fiksno frekvenco). V nekaterih aplikacijah, kot je recimo radar ali merilna tehnika, je pomemben nizek fazni šum. Ta pove, kako ozka in kakšne oblike je spektralna črta signala, ki ga generira oscilator. Tip oscilatorja, pri katerem je v ospredju fazni šum, je predmet te disertacije. Fazni šum se podaja z enotami dBc/Hz. Pri nekem odmiku od nosilca se poda razmerje med močjo šuma in močjo nosilca. Fazni šum je odvisen predvsem od kvalitete resonatorja. Nanj močno vpliva tudi 1/f šum. Ta dva parametra vplivata predvsem na obliko faznega šuma oziroma na fazni šum v bližnjem območju frekvence nihanja oscilatorja. Na absolutno raven vpliva termični šum. Na področju mikrovalovnih oscilatorjev s fiksno frekvenco in nizkim faznim šumom je danes razvitih nekaj konceptov, ki dosegajo izjemne rezultate. Pri nizkošumnih oscilatorjih se v X-frekvenčnem območju pojavljajo različni resonatorji, kot je na primer votlinski ali pa optični resonator. Uporaba votlinskega resonatorja z neobremenjeno kvaliteto 80·103 tako omogoča realizacijo generiranje signala s faznim šumom -75 dBc/Hz pri odmiku 10 Hz. Fazni šum oscilatorja z votlinskim resonatorjem, ki ima v svoji notranjosti nameščen safirjev kristal, vse skupaj pa je ohlajeno na 6 K, dosega fazni šum -125 dBc/Hz pri odmiku 10 Hz od nosilca. Uporaba generatorja optičnega glavnikastega spektra omogoča pri 10 Hz odmika fazni šum -130 dBc/Hz. Vsi trije rezultati so vrhunski in zahtevajo uporabo kompleksnih rešitev in specializiranih komponent. Leta 1995 je bil predstavljen oscilator, ki kot resonator uporablja optično zakasnilno linijo. Optično vlakno zaradi majhnega slabljenja omogoča realizacijo dolgih zakasnilnih časov in s tem visokih kvalitet. Tak oscilator ne potrebuje posebnega resonatorja, nivo faznega šuma pa se določa z dolžino optičnega vlakna. Pomembna prednost tako imenovanega optoelektronskega oscilatorja je tudi neodvisnost faznega šuma od frekvence nihanja. V X-frekvenčnem območju je mogoče doseči fazni šum -70 dBc/Hz pri odmiku 10 Hz od nosilca. Na fazni šum optoelektronskega oscilatorja poleg kvalitete zakasnilne linije vplivata tudi zrnati šum fotodiode in relativni intenzitetni šum laserja. Problem optoelektronskega oscilatorja sta večrodovno nihanje in odvisnost frekvence od temperature. Rešitve, ki zmanjšujejo problem večrodovnega nihanja, so tehnike, kot je vključitev dodatne optične zakasnilne linije ali uporaba tehnike vklenitve na vsiljen signal. Problem temperaturne odvisnosti frekvence se lahko rešuje s temperaturno stabilizacijo ali dodatnim merilnim signalom. Problem rešitev, ki se za omenjena problema pojavljajo v literaturi, je recimo povečanje števila komponent oscilatorja ali pa uporaba posebnih gradnikov. V ta namen so bile v okviru te doktorske disertacije razvite tri metode, ki poenostavijo stabilizacijo s stališča dostopnosti gradnikov. Za stabilizacijo frekvence je bila razvita metoda s povratno krmilno zanko. V tem primeru se frekvenca optoelektronskega oscilatorja meri s pomočjo frekvenčnega diskriminatorja, nato pa se na podlagi informacije o frekvenci spreminja valovna dolžina laserja in s tem posredno lomni količnik vlakna. Tako je mogoče kompenzirati frekvenčne spremembe oscilatorja. Stabilnost frekvence z omenjeno metodo je 0,05 ppm/K. Za reševanje problema večrodovnega nihanja sta bili razviti dve metodi. Prva povečuje slabljenje stranskih rodov s pomočjo dodatne modulacije zanke. Gre za to, da se s pomočjo frekvenčnega mešalnika izlušči samo stranski rod nihanja oscilatorja, s tem pa se nato fazno modulira osnovna zanka oscilatorja. Tako je bilo povečano slabljenje stranskih rodov za 5 dB. Druga metoda vključuje uporabo množilnika kvalitete. To je pozitivna povratna vezava pasovno prepustnega sita. Sito skupaj z množilnikom kvalitete izkazuje manjšo pasovno širino kot samo sito brez množilnika kvalitete. Slabljenje stranskih rodov se v tem primeru poveča za 20 dB, poveča pa se tudi fazni šum (4 dB pri odmiku 1 kHz). Jedro disertacije so štirje mednarodno objavljeni članki, od katerih trije predstavljajo omenjene metode, eden pa je pregledni članek, ki je bil objavljen kot vabljeno predavanje. V disertaciji so objavljeni tudi trije patenti, ki pripadajo posamični novi metodi za stabilizacijo optoelektronskega oscilatorja. Microwave oscillators are nowadays an essential part of measurement equipment and telecommunication systems. They are notable for properties such as long-term stability, tuning range and phase noise. Often, the oscillator’s performance is focused on just one of these properties. For example, time-measuring systems demand a very accurate frequency. The frequency of such an oscillator is fixed and cannot change during the operation of the oscillator. In this case, the long-term stability is very good, but not so the phase noise. However, the latter can be improved by employing additional oscillators. Local oscillators are often voltage controlled, and so the frequency-tuning range is important in this case. A low phase noise is preferred, but is limited because of the lower quality factor of the resonator compared to an oscillator with a fixed frequency. In some applications, such as radar or measuring equipment, the phase noise is the most important parameter. The phase noise describes the width and the shape of the oscillator signal’s spectral line. The oscillator, for which the phase noise is the most important parameter, is the subject of this dissertation. The units for the phase noise are dBc/Hz (decibels below carrier per hertz). The ratio between the signal’s power and the noise at a specified frequency offset from the oscillator’s frequency contains the information about the phase noise. The latter depends mostly on the resonator’s quality factor. The 1/f noise also affects the phase-noise performance. These two parameters have an influence on the phase noise close to the carrier frequency. At larger frequency offsets, the thermal noise dominates. A couple of concepts are developed for microwave oscillators with a fixed frequency and an extremely low phase noise. Different types of resonators can be used, such as a cavity resonator or an optical resonator. A phase noise of -75 dBc/Hz at a frequency offset of 10 Hz can be achieved with a cavity resonator having an unloaded quality factor of 80·103 in the X-band. An X-band oscillator with a cavity resonator that is loaded with a sapphire crystal and cooled down to 6 K achieves a phase noise of -125 dBc/Hz at a 10-Hz offset. With an optical frequency comb, a phase noise of -130 dBc/Hz at a 10-Hz offset is possible to achieve in the X-band. All these results are state of the art and are achieved with complex systems and specialized building blocks. An oscillator that uses an optical delay line as a resonator was presented in 1995. An optical fiber enables the realization of a large delay time and thus a high quality factor. An oscillator of this type does not require a special resonator. The phase-noise level is determined with the length of the optical fiber in the delay line. An important advantage of the so-called opto-electronic oscillator is that the phase noise is independent of the oscillator’s frequency. A phase noise of -70 dBc/Hz at a 10-Hz offset can be achieved with this type of oscillator in the X-band. The photodiode’s shot noise and the laser’s relative intensity noise also have an effect on the phase noise of an opto-electronic oscillator. Multimode oscillation and temperature-dependent frequency drift are some of the problems with an opto-electronic oscillator. Solutions, such as additional optical loops and injection locking, were proposed to suppress the side modes in the spectrum of the opto-electronic oscillator. Any frequency drift can be minimized with temperature stabilization or additional measurement signals. The main problems with solutions presented in literature are, for example, to increase the number of components or the use of highly specialized building blocks. To simplify the structure of an opto-electronic oscillator and to maintain good stability, three methods were developed, which are presented in this dissertation. To stabilize the frequency a method with a feedback control loop was developed. The achieved frequency drift was 0.05 ppm/K. The method works in such a way that the frequency is measured with a frequency discriminator and made constant with the laser’s changing wavelength. The wavelength of the light has an effect on the delay time because of the refractive index and thus also an effect on the oscillator’s frequency. To eliminate the side modes, two methods were developed. One method increases the side-mode suppression with an additional phase modulation of the oscillator’s loop. With a frequency mixer a side mode is extracted from the oscillator’s spectrum. The phase of the oscillator’s loop is then modulated with the extracted signal. A 5-dB increase in the suppression ratio was achieved with this method. The second method includes a quality multiplier, which is a positive feedback, added to a band-pass filter in the oscillator’s loop. The filter’s bandwidth is decreased with this technique, which increases the suppression ratio by 20 dB, according to the measurements presented in this dissertation. Unfortunately, this technique increases the phase noise by 4 dB at a 1-kHz offset. The dissertation’s core is four internationally published scientific papers. Three of them present three methods developed during the research work and are already mentioned in previous paragraphs. One paper is a state-of-the-art review, and was published as an invited paper at a conference. Besides the scientific papers, three patents (one for each of the developed methods) are also presented in this dissertation.

Oscilatorji so neizbežen del vsakršnega vezja, ki je uporabljen v časovno-merilnih in komunikacijskih napravah. Odvisno od naprave je pomembna natančnost in/ali stabilnost frekvence. Pri komunikacijskih napravah je poleg teh dveh parametrov potrebno pri izbiri oscilatorjev upoštevati še količino faznega trepetanja (angl. jitter ). Sistemi, v katerih so oscilatorji uporabljeni, določajo pomen posameznih lastnosti, na odlagi česar vrednotimo ustreznost posameznega tipa. Natančno časovno referenco že nekaj desetletij podpirajo kristalni oscilatorji. V zadnjem času je tehnologija izdelave struktur na siliciju in sama CMOS tehnologija tako napredovala, da na marsikaterem področju zasedajo mesto kristalnih oscilatorjev MEMS in CMEMS oscilatorji, prav tako pa tudi silicijevi oscilatorji na podlagi RLC resonatorjev. Poudarek pričujočega diplomskega dela je na vplivu napajalnih motenj na trepetanje izhodnega signala oscilatorja. V uvodu diplomskega dela je podana kratka zgodovina nastanka oscilatorjev in njihove uporabe. V drugem poglavju je podan pregled tehnologije oscilatorjev in njihovih lastnosti. Teoretično ozadje faznega trepetanja je predstavljeno v tretjem poglavju. Četrto poglavje zajema merilno metodo, predstavitev merilne opreme in izbranih merjencev. Rezultati meritev so podrobno predstavljeni v petem poglavju, vključno z interpretacijo rezultatov meritev. Zadnje, šesto poglavje, pa podaja zaključke in na podlagi njih nasvete pri snovanju napajalnega dela oscilatorjev. Nowadays, majority of circuits include some type of oscillator. They are present in all time-measurement and communication circuits. Type of the system defines required accuracy and/or frequency stability. Additionally, for communication systems, also phase jitter is a key selective parameter. Parameters are weighted according to the system, where the oscillator is used. For many decades, crystal oscillators are selective choice for systems, where accuracy is required. In last ten years, progress in CMOS technology structures allowed development of MEMS and CMEMS oscillators, and also RLC resonator-based oscillators, which can replace crystal oscillators on many fields. Focus of this thesis is on supply noise influence on phase jitter. In the introduction, the thesis presents short history of oscillators and their end use. The second chapter describes different types of oscillators and compares their characteristics. Chapter three presents different jitter types. Measuring method, used equipment and set of tested oscillators is presented in chapter four. Measuring results and their interpretation is presented in fifth chapter. Last, sixth chapter, provides conclusions and directions for most appropriate use of oscillators.