Electronically reconfigurable wideband microwave filters

Many systems require multi function capability in the filter aspects of systems; the method currently used is filter banks which take up a lot of board space. It is thought that reconfigurable filters hold the key to replacing filter banks in order to save board space and thus potentially increasing functionality of the systems. The aim of this research is to develop electronically reconfigurable microwave filters for future communication systems. The project investigates some key design issues of reconfigurable filters. Circuits were modelled and full-wave electromagnetic simulations were performed for the investigation. Experimental work was carried out to demonstrate advanced reconfigurable microwave devices. The components used in each concept investigated were pin diodes due to their superior performance in wideband and high frequency applications. Firstly a single coupled line concept was looked at for bandwidth reconfigurability. This concept was then further developed for industrial applications by simply cascading these sections to obtain a high selective filter. A design method was developed for any number of cascades both with and without an impedance transformer; the use of LCP was used to increase flexibility due to its desirable characteristics. The most desirable outcome would be filter to simultaneously control bandwidth and frequency. In order to tackle this issue the coupled line concept was adapted to incorporate frequency tunability, along with a design method being presented. Furthermore, a cascaded highpass/ lowpass filter was also explored for this concept for added flexibility in the design of a filter capable of control of both bandwidth and center frequency

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

Multi-passband filters and tunable filters design based on coupled resonator circuits

This thesis investigates multi-passband and tunable microwave filters, it includes a new generalised design technique for multi-passband filters and a new coupling tuning structure for tunable waveguide filters. The synthesis technique is an analytical approach and offers very fast solutions to the design once the desired filter specifications are given. The technique calculates the coupling matrix and external Q-factors for a wide range of filter specifications. The centre frequency and bandwidth of each passband, and the number of passbands can all be arbitrarily chosen. To verity the calculations, multi-passband filters are realised by using inverter coupled resonator sections. Two X-band waveguide multi-passband filter examples are given to validate the theory. Besides the innovation in synthesis technique, new designs of fully tunable waveguide filters are also presented. These filters are based on the new coupling tuning structure and a separate frequency tuning structure offering tuning in both centre frequency and bandwidth of the filter. One tunable bandpass filter and one tunable notch filter is implemented in X-band waveguide circuit

Analog Implementation of Fractional-Order Elements and Their Applications

With advancements in the theory of fractional calculus and also with widespread engineering application of fractional-order systems, analog implementation of fractional-order integrators and differentiators have received considerable attention. This is due to the fact that this powerful mathematical tool allows us to describe and model a real-world phenomenon more accurately than via classical “integer” methods. Moreover, their additional degree of freedom allows researchers to design accurate and more robust systems that would be impractical or impossible to implement with conventional capacitors. Throughout this thesis, a wide range of problems associated with analog circuit design of fractional-order systems are covered: passive component optimization of resistive-capacitive and resistive-inductive type fractional-order elements, realization of active fractional-order capacitors (FOCs), analog implementation of fractional-order integrators, robust fractional-order proportional-integral control design, investigation of different materials for FOC fabrication having ultra-wide frequency band, low phase error, possible low- and high-frequency realization of fractional-order oscillators in analog domain, mathematical and experimental study of solid-state FOCs in series-, parallel- and interconnected circuit networks. Consequently, the proposed approaches in this thesis are important considerations in beyond the future studies of fractional dynamic systems

Investigation of advanced Butler matrices with integrated filter functions

This study presents a novel synthesis technique for Butler matrices that include filter transfer functions through a circuit based only on resonators. The Butler matrix is the fundamental building block to split and recombine the signals in Multi-port Power Amplifiers, where multiple inputs are delivered to a bank of amplifiers sharing them, and later recombined through an output network. However, to suppress spurious frequencies generated by the amplifiers or to provide near-band rejection in order not to interfere with other transmission/receiving bands, separate filtering is often required. Here, the traditional properties of the Butler matrix are included together with filtering selectivity into one single device based only on coupled resonators. An analytical synthesis procedure of the coupling matrix is presented here for the first time. The proposed solution has shown significant advantages in terms of size reduction compared to the traditional baseline consisting of a Butler matrix plus a bank of band-pass filters. Based on the technique proposed, three prototypes are designed and manufactured: a 180° hybrid coupler based on resonators and two versions of a 4x4 Butler matrix with filtering, built with additive manufacturing and with milling. Experimental measurements are in good agreement with simulations and theoretical expectations

Analogue filter networks: developments in theory, design and analyses

Not availabl

URI Undergraduate and Graduate Course Catalog 2006-2007

This is a digitized, downloadable version of the University of Rhode Island course catalog.https://digitalcommons.uri.edu/course-catalogs/1058/thumbnail.jp