70 research outputs found
A Multichannel D-Band Radar Receiver with Optimized LO Distribution
No full textThis work presents a multichannel D-band receiver front-end for multiple-input-multiple-output frequency-modulated continuous-wave radar applications. The 120-GHz local oscillator (LO) signal is generated from an external 24-GHz source by an integrated frequency multiplier by five. We propose co-design of power-matched differential buffers with active splitters. Thank to the optimal impedance ratio, the power consumption of the LO distribution network could be minimized. To demonstrate the effectiveness of the discussed method, a chip with three receivers is implemented, where each receiver signal path comprises a mixer-first Gilbert cell which shows 12-dB conversion gain, 13-dB single-sideband (SSB) noise figure, and -5-dBm input-referred 1-dB compression point. A fourth channel is included for built-in self-test and the characterization of the LO distribution chain, providing a -2-dBm output signal over the 111-123-GHz frequency range. The circuit has a low-power consumption of 66-mW per RX channel, for a total power consumption of 198mW from the 1.8-V supply. The active area is 2.07mm2 implemented using a 0.13- {{mu }} ext{m} SiGe BiCMOS technology
Breast Cancer Imaging using a 24 GHz Ultra-Wideband MIMO FMCW Radar: System Considerations and First Imaging Results
No full textMicrowave imaging for breast cancer detection has been widely studied as an alternative technique to the conventional X-ray mammography. The systems developed until now operate at frequencies of a few gigahertz. This limits the achievable image quality. Higher operational frequencies are advantageous for achieving a better resolution, at the expense of a lower penetration depth. The downscaling of components together with an integrated radar transceiver would lead to the development of a compact and cost-effective radar imaging system. This paper investigates the possibility of using an integrated ultra-wideband frequency-modulated continuous-wave (FMCW) radar system operating at a center frequency of 20 GHz and bandwidth of 8 GHz for breast cancer imaging. System considerations are developed to assess the tumor detectability based on the signal attenuation within the breast and the radar sensitivity. A numerical simulation is conducted and first imaging results are presented
HIGHER EDUCATION EXPERIENCES IN KYRGYZSTAN: CASE OF OSH STATE UNIVERSITY
No full textIn this article, author describe some key aspects of higher education reforms and what have been the Osh State University's experiences in relation to these reforms
Hoerschelmann, Karl. Isikuarhiiv
No full text79 säilikutI. Loominguline tegevus. 1. Kirjanduslik looming. 1.1. Luuletused. Poeem, s.1-7. 1.2. Jutustused. Näidendid, s.8-24.1.3. Filosoofilised esseed, s.25-39. 1.4. Kirjandusloolised käsitlused, s.40-43. 2. Kunstilooming, s.44. II. Märkmed. Väljakirjutused vene poeetide loomingust, s.45-49. III. Kirjavahetus, s.50-53. IV. Käsitlused K. Hoerschelmanni kohta, s.54. V. Teiste isikute materjalid. 1. Jelizaveta Hoerschelmanni joonistused. Jelizaveta Hoerschelmanni ja Anna Röderi kirjavahetus jm. materjalid, s.55-70. 2. Jüri Ivaski materjalid, s.71-79. Опись материалов архива К. К. Гершельмана, передаваемых в Отдел рукописей и редких книг Библиотеки Тартуского университета / [koostanud Sergei Issakov], s.79http://www.ester.ee/record=b4002699*es
Schaltungen zur Frequenzumsetzung für drahtlose Übertragungssysteme im Millimeterwellenbereich
No full textDiese Arbeit beschreibt den Entwurf, die Analyse und die Verifikation von integrierten Schaltungen zur Frequenzumsetzung für drahtlose Übertragungssysteme im Millimeterwellenbereich. Bei der Beschreibung der zur Verfügung stehenden Halbleitertechnologien und der Aufbau- und Verbindungstechniken wird deutlich, dass parasitäre Widerstände, Kapazitäten und Induktivitäten sämtlicher Verbindungen Verluste und Reflexionen verursachen, die mit der Signalfrequenz ansteigen. Dies motiviert die Reduktion der Signalfrequenz zur Verringerung dieser Verluste, soweit wie dies in einem Millimeterwellensystem möglich ist.
Neben den in drahtlosen Übertragungssystemen ohnehin erforderlichen Mischern zur Modulation und Demodulation werden in dieser Arbeit auch Frequenzmultiplizierer vorgestellt. Mit diesen Schaltungen ist es möglich, das hochfrequente Trägersignal direkt neben den Mischern zu erzeugen und mit möglichst kurzen Leitungen anzuschließen, sodass die parasitären Verluste dieser Verbindung sowie die Reflexionen minimal werden. Mit Ausnahme der Verbindungen zu den Antennen kann dadurch die Frequenz der restlichen extern anzuschließenden Signale, nämlich des zu übertragenden Basisbandsignals und des subharmonischen LO-Signals, wesentlich verringert werden, wodurch die Verluste insgesamt reduziert werden.
In dieser Arbeit werden dafür zwei Frequenzverdoppler und ein Frequenzversechsfacher vorgestellt, die jeweils mit einer Eingangsfrequenz im Bereich um 30 GHz Ausgangssignale bei 60 GHz bzw. bei 180 GHz erzeugen. Diese drei Schaltungen wurden mit einem Schwerpunkt auf der Unterdrückung unerwünschter Harmonischer und einer gleichzeitig effizienten Erzeugung der gewünschten Harmonischen entworfen. Damit konnte der Stand der Technik für BiCMOS-Frequenzmultiplizierer mit einer Ausgangsfrequenz von bis zu 210 GHz verbessert werden. Sowohl hinsichtlich der absoluten DC-Leistung des Frequenzversechsfachers von lediglich 63 mW, als auch bezüglich der Effizienz (PAE) von 0,28 %, der Verstärkung von 10 dB und der Unterdrückung unerwünschter Harmonischer von bis zu 35 dB sind die erzielten Ergebnisse außerdem besser als von einigen Schaltungen aus leistungsfähigeren III-V-Halbleiterprozessen.
Passend zur Mittenfrequenz von 180 GHz am Ausgang des Frequenzversechsfachers, die auch die Mittenfrequenz des IEEE G-Bands ist, werden außerdem integrierte Aufwärts- und Abwärtsmischer entwickelt, die auf der für Kommunikationssysteme vergleichsweise wenig beachteten Sechstor-Architektur basieren. Die Vorteile der Sechstor-Architektur wurden zuvor bereits bei niedrigeren Frequenzen sowohl mit integrierten als auch mit diskret aufgebauten Schaltungen demonstriert. Ein Ziel dieser Arbeit ist die darauf aufbauende Entwicklung und Untersuchung von integrierten I-Q-Mischern mit dieser Architektur für drahtlose Kommunikationssysteme bei 180 GHz in einem 130 nm-BiCMOS-Prozess. Dafür werden geeignete Detektoren und Reflektoren präsentiert, mit denen die Implementierung in diesem Frequenzbereich möglich ist. Mit den erzielten Ergebnissen konnte jeweils der Stand der Technik für integrierte Sechstor-Aufwärts- und -Abwärtsmischer verbessert werden: Im Fall der Sechstor-Aufwärtsmischer stellen die durchgeführten Messungen die erste Verifikation dieser Architektur im Millimeterwellenbereich dar. Auch im Fall der Abwärtsmischer ist die entworfene Schaltung die erste Realisierung bei einer Mittenfrequenz von über 120 GHz. Die erzielten Ergebnisse zeigen, dass die Sechstor-Architektur im Millimeterwellenbereich für die Anwendung in drahtlosen Übertragungssystemen geeignet ist. Hinsichtlich der HF-Eigenschaften sind die erzielten Ergebnisse vergleichbar mit oder besser als solche, die mit technologisch aufwendigeren und oftmals energieintensiveren Schalter-Mischern, wie z.B. den Gilbert-Mischern, erreicht werden. Darüber hinaus wird anhand von mathematischen Schaltungsanalysen gezeigt, dass sich diese Mischerarchitektur ebenfalls durch ihre gute analytische Modellierbarkeit auszeichnet. Selbst mit stark idealisierten und vereinfachten Modellen kann der Mischgewinn bei 180 GHz mit einer Abweichung zur Messung und zur Simulation von lediglich rund 5 dB berechnet werden.:Kurzfassung
Abstract
Symbolverzeichnis
Vorveröffentlichungen
1. Einleitung
2. Fertigungsprozesse für Schaltungen im Millimeterwellenbereich
2.1. Halbleitertechnologien
2.2. Aufbau- und Verbindungstechnik
2.3. Reduktion von Verlusten mittels Frequenzumsetzung
3. Frequenzmultiplizierer
3.1. Frequenzverdoppler mit Polyphasenfilter
3.2. Frequenzverdoppler mit aktivem und passivem Balun
3.3. Frequenzversechsfacher
3.4. Anwendung in einem Millimeterwellensystem
4. Mischer
4.1. Sechstor-Interferometer
4.2. Sechstor-Abwärtsmischer
4.3. Sechstor-Aufwärtsmischer
5. Zusammenfassung und Ausblick
A. Betragsberechnungen der auslaufenden Wellen des Sechstors
B. Lösung der nichtlinearen Differenzialgleichung
C. Differenzen der Quadrate und Kuben harmonischer Summen
Literaturverzeichnis
DanksagungIn this thesis the design, analysis and verification of integrated circuits for wireless communication systems operating at millimeter waves is presented. During a review of the available manufacturing processes for integrated circuits, printed circuit boards, and interconnects, problems associated with these techniques are identified. Parasitic elements, such as resistors, capacitors, and inductors introduce losses that increase with the signal frequency. This motivates the reduction of the signal frequency wherever possible, so as to reduce these frequency-dependent losses.
To achieve this, millimeterwave up- and downconverting mixers, which are anyway required in wireless systems for the modulation and demodulation of an rf carrier signal, and frequency multipliers for generation of those carrier signals are presented in this thesis. With the frequency multipliers it is possible to generate the carrier signals as spatially close to the mixers as possible, reducing the required length of the connection and the losses and reflecions associated with it. Two frequency doublers and a frequency sixtupler were designed for the conversion of input signals at 30 GHz to output signals at 60 GHz and at 180 GHz, respectively. The designs are focused on an energy-efficient generation of the desired harmonic and a large suppression of other undesired harmonics. In this way, the demonstrated results for the frequency sixtupler at 180 GHz improve the state-of-the-art for both BiCMOS and III-V circuits in terms of power consumption, power added efficiency (PAE), conversion gain and harmonic suppression. With the output frequency at up to 210 GHz and with a dc power consumption of 63 mW, a conversion gain of 10 dB, a PAE of 0.28 %, and a harmonic suppression of 35 dB is reached.
Matching the output frequency of the sixtupler, two quadrature mixers operating at 180 GHz are presented. They are based on the six-port technique, which offers some promising features at millimeter wave frequencies, but is still not very popular for the application in integrated communication systems. Some research has already been conducted on six-port receivers for radar and communication systems operating at lower frequencies, both as integrated circuits and on printed circuit boards. In the case of six-port downconversion mixers, competetive results with discrete III-V diodes and transistors on printed circuit boards were demonstrated, but very little research on integrated realizations has been published to date. One goal of this thesis is therefore to design integrated six-port mixers at 180 GHz and investigate this architecture for the quadrature up- and downconversion in communication systems. Suitable active detectors and reflectors are proposed to enable the implementation of the six-port technique at these frequencies.
In this way, the first implementation of the six-port technique for the upconversion at millimeterwave frequencies is demonstrated. For the downconversion, the rf center frequency at 180 GHz is the highest among six-port implementations to date. The results in terms of rf performance compare well against state-of-the-art switching mixers, such as Gilbert cells. Moreover, the six-port architecture is found to be much simpler in terms of the circuit complexity and it enables the circuit analysis using only simple and idealistic models. With such models, the conversion gain at 180 GHz can be calculated with an error of only about 5 dB. In its minimal realization, a quadrature mixer with a very low dc power consumption can be designed. This makes the six-port technique increasingly attractive as the rf frequency is increased and switching mixers consume a higher dc and rf power.:Kurzfassung
Abstract
Symbolverzeichnis
Vorveröffentlichungen
1. Einleitung
2. Fertigungsprozesse für Schaltungen im Millimeterwellenbereich
2.1. Halbleitertechnologien
2.2. Aufbau- und Verbindungstechnik
2.3. Reduktion von Verlusten mittels Frequenzumsetzung
3. Frequenzmultiplizierer
3.1. Frequenzverdoppler mit Polyphasenfilter
3.2. Frequenzverdoppler mit aktivem und passivem Balun
3.3. Frequenzversechsfacher
3.4. Anwendung in einem Millimeterwellensystem
4. Mischer
4.1. Sechstor-Interferometer
4.2. Sechstor-Abwärtsmischer
4.3. Sechstor-Aufwärtsmischer
5. Zusammenfassung und Ausblick
A. Betragsberechnungen der auslaufenden Wellen des Sechstors
B. Lösung der nichtlinearen Differenzialgleichung
C. Differenzen der Quadrate und Kuben harmonischer Summen
Literaturverzeichnis
Danksagun
Design a novel methodology for the goal-directed control of epitaxial graphene fabrication
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The elusive 2D carbon poly-type was argued more than 70 years ago. Meanwhile, the recent discovery of graphene has proved that such materials can indeed be obtained and are thermodynamically stable. Graphene has demonstrated the unique properties that lead to many innovations in laboratory conditions. However, the current approaches available for the industrial fabrication yield the low graphene quality against the theoretical predictions. Furthermore, any graphene combination with the supporting units causes a newly-induced quality for adaptation to the other condensed matters. Therefore, the unusual ability for sensitive alteration in the external world has turned into a regulation for intended graphene engineering. The submitted investigation has been undertaken to elaborate a novel methodology for the goal-directed control of epitaxial graphene fabrication by using interaction design. This is the most perspective pathway to scale-up production of intended quality subjected to the manufacturing of novel carbide derived carbon (CDC) patterns via interaction with specific substrates under hydrogen halides impact. The graphene layers and structural arrangement of the composite systems, as well as their electronic properties depend on the particular substrate, coherent commensuration of the adjacent units, interaction between them and the physical environment of fabrication. It is crucial to understand the interaction processes leading to stable construction. Density Functional Theory (DFT) implemented in the CASTEP system has been employed in this research in order to develop this knowledge and also to determine how to tune and engineer the band gaps of such composite assemblies. The substrate alternating reconstructions, polarity of surface terminations, commensuration and number of layers, their stacking order and distances between constituting units are taken into consideration for intended simulation. The (3x3) and (√3x√3) reconstructions of 4H-SiC poly-type are the starting points for epitaxial growth (EG) on the Si-face and C-face unit cells. The results of the substrate induced interaction are interpreted via the versatility of band states gradually traced from the dehydrogenated SiC framework to CDC bi-layer. The distinctive feature resulted from the substrate influence is kept as the transitional band for different arrangements and locations in vicinity of the Fermi level. The first buffering C-plane reinforces substrate distinctions between the initial configurations and polarities. The n-type of gap state is the characteristic of the Si-face termination, whereas, the p-type is found for the C-face case. Both structures are devoid of the freestanding graphene signs. The appropriate indications of dominant graphene identity are found for the (0001) - (√3x√3) substrate only, at a close distance between two upper C-planes acceptable for covalent bonds.
As for graphene EG the chemical conversion by using fluorination is employed to avoid the possible damage inspired by initial substrate roughness. The few layered CDC assemblage on the (0001) - (√3x√3) support is trailed via gradual Si – F interaction and SiFx groups penetrating through the bulk. Regular control over potential energy surfaces, minimal energy pathways, transition states and activation barriers enable the indicative indexes for reaction credibility and progress. By means of the Arrhenius equation using the activation energy values the average temperature of 1500 - 2000 C are predicted for the real conversion events. Under these conditions the wet surface etching for the topmost Si-atoms and release of oxidised CDC are accompanied with a complementary promotion mechanism which resulted in a highly ordered graphene structure.Brunel University’s EPSRC Doctoral Training Account and UK Engineering and Physical Sciences Research Council (EPSRC
Inductor-Less Broadband Energy-Efficient Active Balun up to 60GHz
No full textThe paper presents a non-inductive broadband energy-efficient active balun based on a differential pair, intended for use in the input block of a frequency divider for 22nm technology. The developed device can operate in the frequency range from 2 GHz to 60 GHz with a supply voltage of 0.8 V and consume less than 3 mA. The special feature of the developed active balun is that it does not have inductive components, which reduces its size and signal loss. Amplitude of the output signal in working frequency range is from 450 mV to 200 mV. Signal gain in the range from 1-60 GHz varies from -10 dB up to 4 dB. The size of the circuit on the chip is 48x34 um. The device allows you to receive a stable signal at high data transfer rates and provides energy savings due to low current consumption
Integrated CMOS Doppler Radar : Power Amplifier Mixer
No full textThis thesis is based on a paper by V. Issakov, presented 2009, where a circuit of a merged power amplifier mixer solution was demonstrated. This work takes that solution and simplifies it for the use at a lower frequency. The implementation target is a Doppler radar application in CMOS that can detect humans in a range of 5 to 15 meters. This could be used as a burglar alarm or an automatic light switch. The report will present the background of Issakov’s work, basic theory used and the implementation of the final design. Simulations will show that the solution presented work, with a 15 dB conversion loss. This design performs well compared to reference mixers. With this report it will be shown that it is possible to make a simple and compact Doppler radar system in CMOS.Denna avhandling bygger på en artikel av V. Issakov, presenterad 2009, där en lösning för att sammanslå en effektförstärkare med en mixer till en krets visades. Detta arbete tar denna lösning och förenklar det för användning vid en lägre frekvens. Målet är att implementera en dopplerradar i CMOS som kan detektera människor inom ett avstånd på 5 till 15 meter. Denna radar skulle kunna användas som ett inbrottslarm eller en automatisk strömbrytare. Rapporten kommer att presentera bakgrunden från Issakov’s arbete, grundläggande teori som används och genomförandet av det slutliga kretsschemat. Simuleringar visar att den presenterade lösningen fungerar, med en 15 dB konverteringsförlust. Denna konstruktion presterar väl jämfört med referens mixrar. Med denna rapport visas det att det är möjligt att göra ett enkelt och kompakt dopplerradarsystem i CMOS
- …
