Miniaturized High-Q Tunable RF Filters

This dissertation focuses on the investigation and development of novel efficient tuning techniques and the design of miniaturized high-Q tunable RF filters for high-performance reconfigurable systems and applications. First, a detailed survey of the available tuning concepts and state-of-art tunable filters is provided. Then, a novel so-called inset resonator configuration is presented for the applications of fixed and tunable coaxial filters. The design procedure of frequency tunable filters with constant absolute bandwidth (CABW) is described, and various tunable inset filters are implemented, offering many desirable merits, including the wide tuning range and stable high-Q with minimum variation. For wide octave frequency tuning ranges with CABW, a second novel concept is presented using so-called re-entrant caps tuners. Beside simplicity and compactness, this technique also features enhanced spurious performance and wider tuning capabilities than the conventional means. Also, in this dissertation, various miniaturized reconfigurable dual-band/dual-mode bandpass filters and diplexers are presented using compact dual-mode high-Q TM-mode dielectric resonators. Furthermore, a novel microfluidic-based ultra-wide frequency tuning technique for TM010-mode dielectric resonators and filters is introduced in this dissertation. In addition to the very wide tuning window, this mechanism has key advantages of low-cost, simplicity, and intrinsic switch-off. Lastly, the dissertation includes a novel bandwidth reconfiguration concept with multi-octave tuning using a single element for coaxial bandpass filters. This mechanism brings many features including the fast tuning, constant high-Q, intrinsic switch-off, and wide BW-reconfiguration

Analysis and Design of Low-Cost Waveguide Filters for Wireless Communications

The area of research of this thesis is built around advanced waveguide filter structures. Waveguide filters and the waveguide technology in general are renowned for high power capacity, low losses and excellent electromagnetic shielding. Waveguide filters are important components in fixed wireless communications as well as in satellite and radar systems. Furthermore, their advantages and utilization become even greater with increase in frequency, which is a trend in modern communication systems because upper frequency bands offer larger channel capacities. However, waveguide filters are relatively bulky and expensive. To comply with more and more demanding miniaturization and cost-cutting requirements, compactness and economical design represent some of the main contemporary focuses of interest. Approaches that are used to achieve this include use of planar inserts to build waveguide discontinuities, additive manufacturing and substrate integration. At the same time, waveguide filters still need to satisfy opposed stringent requirements like small insertion loss, high selectivity and multiband operation. Another difficulty that metal waveguide components face is integration with other circuitry, especially important when solid-state active devices are included. Thus, improvements of interconnections between waveguide and other transmission interfaces are addressed too. The thesis elaborates the following aspects of work: Further analysis and improved explanations regarding advanced waveguide filters with E-plane inserts developed by the Wireless Communications Research Group, using both cross coupled resonators and extracted pole sections (Experiments with higher filter orders, use of tuning screws, degrees of freedom in design, etc. Thorough performance comparison with competing filter technologies) - Proposing novel E-plane filter sections with I-shaped insets - Extension of the E-plane filtering structures with metal fins to new compact dual band filters with high frequency selectivity and miniaturized diplexers. - Introduction of easy-to-build waveguide filters with polymer insert frames and high-performance low-profile cavity filters, taking advantage of enhanced fabrication capabilities when using additive manufacturing - Developing new substrate integrated filters, as well as circuits used to transfer signals between different interfaces Namely, these are substrate integrated waveguide to metal waveguide planar transitions that do not require any modifications of the metal waveguides. Such novel transitions have been designed both for single and orthogonal signal polarizations

High-Q Multi-band Filters

Recent development of multifunctional communication systems capable of processing large amount of data has triggered the demand for novel payload configurations with advanced filtering functions. To increase the payload flexibility, a large number of multiplexer and filter networks with different frequency plans are usually employed for the transmitting downlink. Multi-band filters are the required function in many cases for minimizing integration complexity and reducing size and mass of space systems. The multi-band filters combine the frequency spectrums of non-contiguous channels before transmitting through antenna beams, and provide sufficient rejection to the frequency spectrums of the adjacent channels, thus maintaining a high signal-to-interference ratio especially in multi-beam frequency-reuse communication systems. Traditional approaches to realize multi-band filters do not offer advantages in terms of size and mass reduction. Multi-mode resonators have the advantage of size reduction; however they are not often used in multi-band applications due to the challenges of operating the multiple modes in prescribed passbands simultaneously. The main research objective of this thesis is to investigate the feasibility of designing multi-band filters based on high-Q multi-mode resonators. Various multi-mode waveguide and dielectric resonators are explored to realize multi-band filters. The proposed multi-band filters do not require junctions and can achieve an equivalent performance with fewer cavities, thus significantly reducing the footprint when compared to traditional approaches. Furthermore, tunable multi-band filters with a constant absolute bandwidth and minimum degradation during the tuning process is investigated and developed. A systematic design approach of designing multi-band filters based on multi-mode resonators is established in this work starting from the coupling-matrix synthesis of the multi-band network. Following that, dual-band filters based on elliptical and rectangular dual-mode resonators are proposed. The two passbands of the dual-band filter are carried by two independent cavity modes and realized by an inline direct-coupled configuration. The inline dual-band filter design can convert to a diplexer structure by modifying the output ports at the end-resonators. To improve near-band frequency selection of both channels, multiple configurations to realize quasi-elliptic dual-band filter functions are proposed. The first quasi-elliptic design is based on a combination of dual-mode and single-mode rectangular resonators resulting in multiple transmission zeros and improved spurious response. The second structure is a side-coupled design based on dual-quadruplet configuration featuring a pair of transmission zeros on each of the passband and a very compact layout. Limitations of the quasi-elliptic design are investigated and modified structures have been proposed with improved RF performances. Triple-band filters are realized by three types of high-Q cavity resonator structures. Each cavity resonator employs triple-modes with resonant frequencies associated with the three passbands. The first design was an elliptical waveguide triple-band filter with an in-line configuration. Each passband of the filter was controlled by a dedicated polarization and represented by an inline direct-coupled set of resonators. The second design was a rectangular-cavity triple-band filter with a folded configuration. The folded configuration overcomes a number of drawbacks from the elliptical in-line design including an improved tunability and ease of assembly. The last design was a triple-band filter design based on dielectric loaded cavity resonators. The unique dielectric resonator structure results in triple-band filters having a very compact size, high Q, and stable thermal response. Further adding tuning capability to the multi-band filter can provide an additional degree of flexibility for the communication payload. A tunable multi-band filter with a constant absolute bandwidth is developed based on combline resonator and requiring only a single tuning element. The performance is demonstrated with an in-house-developed tuning station. It achieves a constant selectivity over a tuning range of 170 MHz and an unloaded Q better than 3000. The novel filter configurations proposed in this thesis promise to be useful not only for satellite payload applications but also for a wide range of wireless base station applications

Coupled resonator based wireless power transfer for bioelectronics

Implantable and wearable bioelectronics provide the ability to monitor and modulate physiological processes. They represent a promising set of technologies that can provide new treatment for patients or new tools for scientific discovery, such as in long-term studies involving small animals. As these technologies advance, two trends are clear, miniaturization and increased sophistication i.e. multiple channels, wireless bi-directional communication, and responsiveness (closed-loop devices). One primary challenge in realizing miniaturized and sophisticated bioelectronics is powering. Integration and development of wireless power transfer (WPT) technology, however, can overcome this challenge. In this dissertation, I propose the use of coupled resonator WPT for bioelectronics and present a new generalized analysis and optimization methodology, derived from complex microwave bandpass filter synthesis, for maximizing and controlling coupled resonator based WPT performance. This newly developed set of analysis and optimization methods enables system miniaturization while simultaneously achieving the necessary performance to safely power sophisticated bioelectronics. As an application example, a novel coil to coil based coupled resonator arrangement to wirelessly operate eight surface electromyography sensing devices wrapped circumferentially around an able-bodied arm is developed and demonstrated. In addition to standard coil to coil based systems, this dissertation also presents a new form of coupled resonator WPT system built of a large hollow metallic cavity resonator. By leveraging the analysis and optimization methods developed here, I present a new cavity resonator WPT system for long-term experiments involving small rodents for the first time. The cavity resonator based WPT arena exhibits a volume of 60.96 x 60.96 x 30.0 cm3. In comparison to prior state of the art, this cavity resonator system enables nearly continuous wireless operation of a miniature sophisticated device implanted in a freely behaving rodent within the largest space. Finally, I present preliminary work, providing the foundation for future studies, to demonstrate the feasibility of treating segments of the human body as a dielectric waveguide resonator. This creates another form of a coupled resonator system. Preliminary experiments demonstrated optimized coupled resonator wireless energy transfer into human tissue. The WPT performance achieved to an ultra-miniature sized receive coil (2 mm diameter) is presented. Indeed, optimized coupled resonator systems, broadened to include cavity resonator structures and human formed dielectric resonators, can enable the effective use of coupled resonator based WPT technology to power miniaturized and sophisticated bioelectronics

Active Backscattering Positioning System Using Innovative Harmonic Oscillator Tags for Future Internet of Things: Theory and Experiments

RÉSUMÉ D'ici 2020, l'Internet des objets (IoT) permettra probablement de créer 25 milliards d'objets connectés, 44 ZB de données et de débloquer 11 000 milliards de dollars d’opportunités commerciales. Par conséquent, ce sujet a suscité d’énormes intérêts de recherche dans le monde académique entier. L'une des technologies clés pour l'IoT concerne le positionnement physique intérieur précis. Le principal objectif dans ce domaine est le développement d'un système de positionnement intérieur avec une grande précision, une haute résolution, un fonctionnement à plusieurs cibles, un faible coût, un faible encombrement et une faible consommation d'énergie. Le système de positionnement intérieur conventionnel basé sur les technologies de Wi-Fi ou d'identification par radiofréquence (RFID) ne peut répondre à ces exigences. Principalement parce que leur appareil et leur signal ne sont pas conçus spécialement pour atteindre les objectifs visés. Les chercheurs ont découvert qu'en mettant en oeuvre de différents types de modulation sur les étiquettes, le radar à onde continue (CW) et ses dérivés deviennent des solutions prometteuses. Les activités de recherche présentées dans cette thèse sont menées dans le but de développer des systèmes de positionnement en intérieur bidimensionnel (2-D) à plusieurs cibles basées sur des étiquettes actives à rétrodiffusion harmonique avec une technique à onde continue modulée en fréquence (FMCW). Les contributions de cette thèse peuvent être résumées comme suit: Tout d'abord, la conception d'un circuit actif harmonique, plus spécifiquement une classe d'oscillateurs harmoniques innovants utilisée comme composant central des étiquettes actives dans notre système, implique une méthodologie de conception de signal de grande taille et des installations de caractérisation. L’analyseur de réseau à grand signal (LSNA) est un instrument émergent basé sur les fondements théoriques du cadre de distorsion polyharmonique (PHD). Bien qu'ils soient disponibles dans le commerce depuis 2008, des organismes de normalisation et de recherche tels que l’Institut national des normes et de la technologie (NIST) des États-Unis travaillent toujours à la mise au point d'un standard largement reconnu permettant d'évaluer et de comparer leurs performances. Dans ce travail, un artefact de génération multi-harmonique pour la vérification LSNA est développé. C'est un dispositif actif capable de générer les 5 premières harmoniques d'un signal d'entrée avec une réponse ultra-stables en amplitude et en phase, quelle que soit la variation de l'impédance de la charge.----------ABSTRACT By 2020, the internet of things (IoT) will probably enable 25 billion connected objects, create 44 ZB data and unlock 11 trillion US dollar business opportunities. Therefore, this topic has been attracting tremendous research interests in the entire academic world. One of the key enabling technologies for IoT is concerned with accurate indoor physical positioning. The development of such an indoor positioning system with high accuracy, high resolution, multitarget operation, low cost, small footprint, and low power consumption is the major objective in this area. The conventional indoor positioning system based on WiFi or radiofrequency identification (RFID) technology cannot fulfill these requirements mainly because their device and signal are not purposely designed for achieving the targeted goals. Researchers have found that by implementing different types of modulation on the tags, continuous-wave (CW) radar and its derivatives become promising solutions. The research activities presented in this Ph.D. thesis are carried out towards the goal of developing multitarget two-dimensional (2-D) indoor positioning systems based on harmonic backscattering active tags together with a frequency-modulated continuous-wave (FMCW) technique. Research contributions of this thesis can be summarized as follows: First of all, the design of a harmonic active circuit, more specifically, a class of innovative harmonic oscillators used as the core component of active tags in our system, involves a large signal design methodology and characterization facilities. The large signal network analyzer (LSNA) is an emerging instrument based on the theoretical foundation for the Poly-Harmonic Distortion (PHD) framework. Although they have been commercially available since 2008, standard and research organizations such as the National Institute of Standards and Technology (NIST) of the US are still working towards a widely-recognized standard to evaluate and cross-reference their performances. In this work, a multi-harmonic generation artifact for LSNA verification is developed. It is an active device that can generate the first 5 harmonics of an input signal with ultra-stable amplitude and phase response regardless of the load impedance variation

Solid-state microwave heating for biomedical applications

The research conducted in this thesis aims to develop an efficient microwave delivery system employing miniature resonant microwave cavities, targeted at compact, flexible and ideally field-deployable microwave-assisted diagnostic healthcare applications. The system comprises a power amplifier as a solid-state microwave source and a load - as a single mode cavity resonator to hold the sample. The compactness of the practical microwave delivery system relies on the direct integration of the sample-holding cavity resonator to the power amplifier and inclusion of the built-in directional coupler for power measurements. The solid state power transistors used in this research (10W-LDMOS, 10W-GaN) were provided by the sponsoring company NXP Inc. In practical microwave delivery applications, the impedance environment of the cavity resonators change significantly, and this thesis shows how this can be systematically utilized to present the optimal loading conditions to the transistor by simply designing the series delay lines. This load transfer technique, which critically can be achieved without employing bulky, lossy and physically larger output matching networks, allows high performance of the power amplifier to be achieved through waveform engineering at the intrinsic plane of the transistor. Starting with the impedance observation of a rectangular cavity, using only series delay lines allowed the practical demonstration of the high power and high efficiency fully integrated inverse class-F (F-1) power amplifier. Temperature is an important factor in a microwave heating and delivery system as it changes the impedance environment of the cavity resonator. This natural change in both cavity and sample temperature can be accommodated through simplified series matching lines and the microwave heating system capable of working over substantial bandwidth was again practically demonstrated. The inclusion of the coupler maintained the compactness of the system. In the practical situations envisaged, the microwave delivery system needs to accommodate natural variation between sample volumes and consistencies for heating. The experimental work considered the heating of different sample volumes ii of water, and characterizing the change in the natural impedance environment of the cavity as a result. It was shown how the natural impedance variation can not only be accommodated, but also exploited, allowing ‘continuous’, high-efficiency performance to be achieved while processing a wide range of sample volumes. Specifically, using only transistor package parasitic, the impedance of the cavity itself together with a single series microstrip transmission line allows a continuous class-F-1 mode loading condition to be identified. Through different experiments, the microwave delivery systems with high-performance are demonstrated which are compact, flexible and efficient over operational bandwidth of the cavity resonators

Microwave apparatus for gravitational waves observation

In this report the theoretical and experimental activities for the development of superconducting microwave cavities for the detection of gravitational waves are presented.Comment: 42 pages, 28 figure

Investigation and development of a transverse deflecting structure: a beam separator for ELBE

The thesis described the development of a beam separator device for the ELBE accelerator in Dresden, Germany, facilitating simultaneous operation of multiple secondary user stations. After reviewing deflecting structures, an RF cavity was chosen as the optimal solution. Extensive electromagnetic and multiphysics analysis were conducted to optimize the cavity design. A copper deflecting cavity was manufactured and underwent rigorous high-power testing, successfully meeting the design requirements. The cavity is now ready for installation in the ELBE beamline.In dieser Arbeit wurde die Entwicklung einer Strahlseparatorvorrichtung für den ELBE-Beschleuniger in Dresden beschrieben, die den gleichzeitigen Betrieb mehrerer sekundärer Benutzerstationen ermöglicht. Nach der Prüfung von Ablenkungsstrukturen wurde eine HF-Kavität als optimale Lösung gewählt. Umfangreiche elektromagnetische und multiphysikalische Analysen wurden durchgeführt, um das Design des Hohlraums zu optimieren. Ein Ablenkungshohlraum aus Kupfer wurde hergestellt und strengen Hochleistungstests unterzogen, wobei die Designanforderungen erfolgreich erfüllt wurden