Substrate Integrated Waveguide (SIW) and Superconducting Filters

Substrate integrated waveguides (SIW) provide an excellent compromise between size and loss reduction for applications in planar circuits. SIW filters provide a better Q-factor than microstrip filters and a significant reduction in size compared to waveguide filters. The use of multi-band filters has become increasingly more common because they provide the opportunity to reduce the total footprint in both RF transmitters and receivers. This thesis investigates the design process of a single-band quasi-elliptic and dual-band SIW filter. We use several methods to design the single-band SIW, and compare the simulated results of each. These filters are designed on 0.508mm thick Rogers4003C substrate, fabricated, and measured. The introduction of negative cross-coupling in SIW structures is achieved by using etched coplanar waveguide (CPW) lines. This negative cross-coupling allows for the introduction of transmission zeros in both designed filters. We carefully investigate the transition technology to ensure that we achieve a wideband match between microstrip and SIW. The thickness of the substrate provides some challenges in the matching, so we take extra consideration to overcome this. The second part of this thesis explores the design of lumped element superconducting bandpass filters. When designing filters in the kHz and MHz range, several challenges arise. The first is the ability to use certain software: Sonnet and HFSS both have a limited ability to simulate low-frequency components. More specifically, Sonnet demonstrates an inability to accurately simulate inductors, while simulation times in HFSS are prohibitively long. Momentum thus proves to be the best EM simulator for this task. The second challenge is the need to miniaturize these filters. At such low frequencies, the filter’s footprint is quite large, therefore the reduction in size is extremely important. We implement traditional methods, such as stacked spiral inductors and vertically integrated capacitors, and achieve further size reduction by modifying the circuit topology to reduce the components with the largest footprints. We also introduce transmission zeros to improve the upper and lower band rejection. We then design a three-pole classical Chebyshev filter and a three-pole quasi-elliptic filter that uses a miniaturized circuit topology. Finally, we design a 10% six-pole superconducting slotline resonator filter. Slotline resonators provide an excellent quality factor, even at higher frequencies. A CPW-to-slotline transition is implemented so that the device can be measured using a ground-signal-ground probe. The resonators implemented use dual-spiral inductors and interdigital capacitors. This allows for flexibility when choosing the resonant frequency. All superconducting filters are fabricated using the MIT-Lincoln Lab (MIT-LL) multilayer niobium fabrication process

Mapping the potential for decentralized energy generation based on RES in Western Balkans

Although the countries of the Western Balkans are mostly electrified, there are still regions which do not have access to the electricity network or where the network capacity is insufficient. For the most part such areas are under special care of the state (i.e. underdeveloped, devastated by war, depopulated), on islands or in mountainous regions. Since the decentralized energy generation covers a broad range of technologies, including many renewable energy technologies that provide small-scale power at sites close to the users, such concept could be of interest for these locations. This paper identfies the areas in Western Balkans where such systems could be applied Consideration is given to geographical locations as well as possible applications. Wind hydro, solar photovoltaic, and biomass conversion systems were taken into consideration. Since the renewable energy sources data for Western Balkans region are rather scarce, the intention was to give a survey of the present situation and an estimate of future polential for decentralized energy generation based on renewable energy sources. The decentralized energy generation based on renewable energy sources in Western Balkans will find its niche easier for the users that will produce electricity for their own needs and for the users located in remote rural areas (off-grid applications)