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FDTD is a numerical method that uses the second-order central-difference method to discrete the Maxwell¡¦s equations in differential form, and positioning electromagnetic field in space grids and time grids. It is applied to analyze many electromagnetic problems in time domain. In this report the FDTD method is extended to include lumped-elements (as resistor, inductor, capacity),and nonlinear elements(as diode, transistor) to combine the circuit elements and electromagnetic fields, it¡¦s so called LE-FDTD algorithm. The first, we will introduce the theory derivations and simulate some circuit structures in 2D, and then in order to simulate the real circuits, we will extend this algorithm in 3D to make full-wave analysis.

Calculations on stress, strain and deformation are typically made using finite element methods (FEM). An alternative to this is a rigid bodydynamics approach also called lumped element method (LEM). LEM implements deformation by replacing single rigid bodies with multiple subbodies, which are in turn connected with joints (also called constraints) that allow movement between the sub-bodies. If instead of FEM, a lumped element method is used to simulate deformable objects, sufficient accuracy can be obtained at a much lower cost, complexity-wise. A lumped element method-approach could for example achieve real-time simulationspeed. The purpose of this thesis is to expand upon previous work into LEM, analyzing how the rigid bodies and constraints should be configured to produce accurate results for a wider range of objects. Specifically, beams of varying cross section and curved beam axis, as well as other test cases. The simulated values are compared with the analytic predictions given by Euler-Bernoulli beam theory. These simulations are implemented using the AGX Dynamics physics engine from Algoryx Simulation AB. One intended application area of LEM is crane arms. This motivates the focus on analyzing how LEM behaves when simulating beams, as they represent the most basic version of crane arms. Simulation and testing of full crane objects was unfortunately not accomplished, partly due to a lack of convenient testing data. Further work is needed to confirm that LEM behaves well for these expanded cases as well. In addition to the analysis section above, the purpose is also to implement a pipeline for automatic conversion of a CAD-model to a lumped element version in AGX. Specifically, a CAD-model given in the 3D-modeling software SpaceClaim.

Strong demands for smaller, cheaper, and multifunction wireless systems have put very stringent requirements on passive devices, such as inductors and capacitors. This is especially true considering the size and weight of most radio frequency (RF) transceivers are mainly due to passives. RF micro-electro-mechanical-systems (MEMS) passives are addressing this issue by offering lower power consumption and losses, higher linearity and quality (<i>Q</i>)-factors, potential for integration and miniaturization, and batch fabrication. These advantages position RF MEMS passives as good candidates to replace conventional passives. Further, they also open an opportunity for using the passives as building blocks for lumped element-based RF circuits (e.g. Flters, couplers, etc.) which could replace the more-bulky distributed-element circuits.<p> This thesis presents the design, simulation, fabrication using the deep X-ray lithography process, and testing of thick-metal RF inductors and their applications to lumped-element low-pass Filter (LPF) circuits. The 70-um tall single-turn loop inductors are structurally compatible to a pre-existing RF MEMS capacitor concept and allow the two device types to be fabricated together. This compatibility issue is crucial if they would be used to construct more complex RF circuits.<p> At a 50-Ohm inductive reactance point, test results show <i>Q</i>-factors of 17- 55, self-resonant frequencies (SRF) exceeding 11 GHz, and nominal inductances of 0.4- 3 nH for 1-loop inductors and <i>Q</i>-factors of 11- 42, SRFs of 4- 22 GHz, and inductances of 0.8- 5.5 nH for 2-loop inductors. Further, test results reveal that high conductivity metals improve the <i>Q</i>-factors, and that low dielectric-constant substrates increase the SRFs.<p> In terms of LPFs, measurements show that they demonstrate the expected third-order Chebyshev response. Two nickel Filters on a quartz glass substrate show a 0.6-dB ripple with 3-dB frequencies (<i>f</i>-3dB) of 6.1 GHz and 11.9 GHz respectively. On an alumina substrate, they exhibit a 1.4-dB ripple with <i>f</i>-3dB of 5.4 GHz and 10.6 GHz respectively. The filters are 203- 285 um tall and feature 6- 6.5 um wide capacitance air gaps. These dimensions are different than the original designs and the filter performances were shown to be somewhat sensitive to these discrepancies. Compared to a distributed approach, the lumped-element implementations led to an area reduction of up to 95%.

Superconducting microelectronics (SME) technology has the potential of realizing very high speed digital receivers capable of performing direct digitization of radio frequency signals with very low power consumption. The SME receiver is implemented on a single chip using Niobium based low temperature superconductive (LTS) Josephson Junction (JJ) technology by HYPRES. Analogue RF filters are still required at the receiver front end and are key components of the overall superconductor digital receiver. SME receivers usually require two types of RF filters; a wideband bandpass filter and a bandstop filter (a notch filter). The notch filter is required to eliminate interference and unwanted signals in the passband. In this thesis, design of highly miniaturized lumped element wideband and bandstop filters is investigated and some challenges are addressed. The filters are fabricated by the HYPRES process and therefore can be integrated with the SME receiver on the same chip. In a wideband filter, the coupling between the adjacent resonators is high. Achieving such a strong coupling is one of the challenges of designing wideband filters. The wideband filters realized with distributed elements usually suffer from very low spurious frequency. As the bandwidth of the filter becomes wider, the spurious peak of the second harmonic gets closer to the passband of the filter. In the first part of this work, the possibility of realizing lumped element superconducting bandpass filters (BPF) with a relative bandwidth of 80% is investigated. In the second part of the thesis, design and realization of lumped element superconducting bandstop filters (BSF) is discussed. The challenge for designing a bandstop filter is providing a good match over a wide frequency range. So narrowband inverters cannot be used. Instead, usually λ/4 matched transmission lines provide 90° phase shift between the resonators of a notch filter. The possibility of replacing the long transmission line with other means or eliminating the inverters and using both shunt and series resonators are investigated. Having both series and shunt resonators introduces some new challenges that are addressed in the thesis and discussed thoroughly. A tunable notch resonator is presented. The tunability is provided by a superconducting MEMS varactor that is realized in our group by doing some post processing on the device fabricated by HYPRES. The tunability range of the device at cryogenic temperatures is investigated. A 3-pole tunable BSF is also designed that uses the same tunable resonators. The tunability of the filter is investigated through simulation.

Strong demands for smaller, cheaper, and multifunction wireless systems have put very stringent requirements on passive devices, such as inductors and capacitors. This is especially true considering the size and weight of most radio frequency (RF) transceivers are mainly due to passives. RF micro-electro-mechanical-systems (MEMS) passives are addressing this issue by offering lower power consumption and losses, higher linearity and quality (<i>Q</i>)-factors, potential for integration and miniaturization, and batch fabrication. These advantages position RF MEMS passives as good candidates to replace conventional passives. Further, they also open an opportunity for using the passives as building blocks for lumped element-based RF circuits (e.g. Flters, couplers, etc.) which could replace the more-bulky distributed-element circuits.<p> This thesis presents the design, simulation, fabrication using the deep X-ray lithography process, and testing of thick-metal RF inductors and their applications to lumped-element low-pass Filter (LPF) circuits. The 70-um tall single-turn loop inductors are structurally compatible to a pre-existing RF MEMS capacitor concept and allow the two device types to be fabricated together. This compatibility issue is crucial if they would be used to construct more complex RF circuits.<p> At a 50-Ohm inductive reactance point, test results show <i>Q</i>-factors of 17- 55, self-resonant frequencies (SRF) exceeding 11 GHz, and nominal inductances of 0.4- 3 nH for 1-loop inductors and <i>Q</i>-factors of 11- 42, SRFs of 4- 22 GHz, and inductances of 0.8- 5.5 nH for 2-loop inductors. Further, test results reveal that high conductivity metals improve the <i>Q</i>-factors, and that low dielectric-constant substrates increase the SRFs.<p> In terms of LPFs, measurements show that they demonstrate the expected third-order Chebyshev response. Two nickel Filters on a quartz glass substrate show a 0.6-dB ripple with 3-dB frequencies (<i>f</i>-3dB) of 6.1 GHz and 11.9 GHz respectively. On an alumina substrate, they exhibit a 1.4-dB ripple with <i>f</i>-3dB of 5.4 GHz and 10.6 GHz respectively. The filters are 203- 285 um tall and feature 6- 6.5 um wide capacitance air gaps. These dimensions are different than the original designs and the filter performances were shown to be somewhat sensitive to these discrepancies. Compared to a distributed approach, the lumped-element implementations led to an area reduction of up to 95%.

In this report the analysis of microstrip electrodynamic structures on basis of high-temperature superconductors is carried out and a mathematical model of microstrip devices with lumped and distributed nonlinear properties is created. For this purpose nonlinear integral equations method and method of moments are used. In the issue of the work a SHF filter based on the equivalent circuit of elements with lumped parameters is also studied. It is ascertained that the received mathematical model allows to achieve more proper results of modeling on compensation of variation of current-density distribution nearby the edges of conductor break.

Flow control is an area of research of particular interest within automotive and aerospace industries since methods used to affect the fluid flow around vehicles can reduce drag and therefore lower their fuel consumption. One of these methods, which has generated a lot of interest in later years, is called active flow control and uses different types of actuators to impact the surrounding flow. In this thesis a model of a piezoelectric actuator for active flow control has been developed using Lumped Element Modelling and equivalent circuits. This approach, together with the chosen software for implementation, Simulink, provides models which are easy to simulate and evaluate. The actuator model has been validated using a novel methodology with sub-models with the purpose of reducing computational costs. The actuator is therefore divided into two submodels,one for structural and one for fluid dynamics, which are validated separately. This enables the use of simple yet accurate FEM and CFD models instead of time consuming FSI software which the complete model requires. The three implemented models have been validated using cases presented in previous studies and data from CFD-simulations. The results show that the decoupled models can be validated separately and its results can be integrated into the complete model, although further tests with a real actuator is needed. In addition to the modelling, a parameter study of the actuator has been performed in order to prepare for prototype design.

Superconducting microelectronics (SME) technology has the potential of realizing very high speed digital receivers capable of performing direct digitization of radio frequency signals with very low power consumption. The SME receiver is implemented on a single chip using Niobium based low temperature superconductive (LTS) Josephson Junction (JJ) technology by HYPRES. Analogue RF filters are still required at the receiver front end and are key components of the overall superconductor digital receiver. SME receivers usually require two types of RF filters; a wideband bandpass filter and a bandstop filter (a notch filter). The notch filter is required to eliminate interference and unwanted signals in the passband. In this thesis, design of highly miniaturized lumped element wideband and bandstop filters is investigated and some challenges are addressed. The filters are fabricated by the HYPRES process and therefore can be integrated with the SME receiver on the same chip. In a wideband filter, the coupling between the adjacent resonators is high. Achieving such a strong coupling is one of the challenges of designing wideband filters. The wideband filters realized with distributed elements usually suffer from very low spurious frequency. As the bandwidth of the filter becomes wider, the spurious peak of the second harmonic gets closer to the passband of the filter. In the first part of this work, the possibility of realizing lumped element superconducting bandpass filters (BPF) with a relative bandwidth of 80% is investigated. In the second part of the thesis, design and realization of lumped element superconducting bandstop filters (BSF) is discussed. The challenge for designing a bandstop filter is providing a good match over a wide frequency range. So narrowband inverters cannot be used. Instead, usually λ/4 matched transmission lines provide 90° phase shift between the resonators of a notch filter. The possibility of replacing the long transmission line with other means or eliminating the inverters and using both shunt and series resonators are investigated. Having both series and shunt resonators introduces some new challenges that are addressed in the thesis and discussed thoroughly. A tunable notch resonator is presented. The tunability is provided by a superconducting MEMS varactor that is realized in our group by doing some post processing on the device fabricated by HYPRES. The tunability range of the device at cryogenic temperatures is investigated. A 3-pole tunable BSF is also designed that uses the same tunable resonators. The tunability of the filter is investigated through simulation.

Acoustic resonators, such as the Helmholtz and quarter-wave resonator, can be used to attenuate unwanted noise in an enclosed space. Classical formulations can be used to approximate resonator performance for a given resonator configuration, but may lack sufficient accuracy for some applications. This research aims to improve the analytical characterization of resonators to provide better correlation to experimental results. Using higher-order approximations and proper end corrections, more accuracy can be obtained in calculating the impedance and resonance frequency of a single resonator, which will then carry over into the overall configuration of the model. The impedance of a system of resonators in parallel is also considered, where the effects of acoustic coupling can be observed. Resonators with complex, non-ideal geometries are explored for applications where space is limited. The effects of tapers and toroidal curves are considered using impedance translation methods. These theoretical predictions are found to compare favorably with empirical data. Coupling between an enclosure and resonator system is explored experimentally. The effects of resonator placement, damping, and relative cavity and enclosure volume are considered. These data are used to design and test a resonator system with 10 dB of attenuation over a bandwidth of 10 Hz.