In this thesis, we propose and demonstrate a simple and precise method for measuring mm scaled cell gap by using terahertz time domain spectroscopy (THz-TDS) system. This method allows us to measure the cell gap from 15mm to 1.5mm. In addition, the accuracy of measured thickness for the proposed method is also discussed and analyzed. Meanwhile, a nematic liquid crystal BL006 with birefringence as high as 0.27 in THz frequency range and its optical properties of cholesteric liquid crystal (CLC) as mixing chiral materials are investigated and reported. The ordinary refractive index and average effective refractive index at 20oC are from 1.52 to 1.56 and from 1.61 to 1.64, respectively, in THz frequency ranging from 0.2 THz to 1.4THz. In addition, we also demonstrate that cell filled with CLC is with polarization independent property for THz radiation. Through the 5mm cell filled CLC with diluted concentration of the dopant chiral material for decreasing the critical voltage, an electric controlled polarization independent phase shifter with the modulation depth exceeding 2pi is demonstrated. Furthermore, we also investigate the driving field dependence of phase retardation and discuss the reliability.

Modern phased array radars require large numbers of electronically controlled phase shifters to steer their beams to the desired direction. The amount of beam steering error depends on the phase resolution of the phase shifters as well as the performance of other parts of the antenna system. The size of the phase shifter in such systems is most of the time needed to be small, which necessitates the MMIC implementation. In the context of this thesis, an X band 7 bit MMIC phase shifter of 2.8125 degree phase resolution, including its layout, is designed using the design kit of OMMIC&reg / Foundry. All bits of the phase shifter are designed to have low return loss so as to minimize the performance egradation due to loading effects upon cascading. Also some structures studied using the design kit of WIN&reg / Foundry are presented. Both designs were performed using ADS&reg / . For the optimum cascading of 7 bits, a MATLAB code was written and used.

This thesis presents a novel monolithic phased array implemented using the RF MEMS technology. The structure, which is designed at 15 GHz, consists of four linearly placed microstrip patch antennas, 3-bit distributed RF MEMS low-loss phase shifters, and a corporate feed network. The RF MEMS phase shifter employed in the system consists of three sections with a total of 28 unit cells, and it occupies an area of 22.4 mm &amp / #61620 / 2.1 mm. The performance of the phase shifters is improved using high-Q metal-air-metal capacitors in addition to MEMS switches as loading elements on a high-impedance coplanar waveguide transmission line. The phased array is fabricated monolithically using an in-house surface micromachining process, where a 1.2-&amp / #61549 / m thick gold structural layer is placed on a 500-&micro / m thick glass substrate with a capacitive gap of 2 &amp / #61549 / m. The fabrication process is simple, requires only 6 masks, and allows the implementation of various RF MEMS components on the same substrate, such as RF MEMS switches and phase shifters. The fabricated monolithic phased array occupies an area of only 6 cm &amp / #61620 / 5 cm. The measurement results show that the phase shifter can provide nearly 20&amp / #61616 / /50&amp / #61616 / /95&amp / #61616 / phase shifts and their eight combinations at the expense of 1.5 dB average insertion loss at 15 GHz. The phase shifters can be actuated with 16 V, while dissipating negligible power due to its capacitive operation. It is also shown by measurements that the main beam can be steered to 4&amp / #61616 / and 14&amp / #61616 / by suitable settings of the RF MEMS phase shifters.

This thesis presents the theory, design, fabrication, and measurement results of novel reconfigurable impedance tuner, phase shifter, and vector modulators using the RF MEMS technology. The presented circuits are based on triple stub topology, and it is shown both theoretically and experimentally in this thesis that it is possible to control the insertion phase and amplitude of the input signal simultaneously using this topology. The presented circuits are implemented using an in-house, surface micromachining fabrication process developed at METU, namely METU RF MEMS Fabrication Process, which is implemented using six masks on quartz substrates. The RF MEMS impedance tuner is designed to operate in 6-20 GHz frequency band, and it covers the Smith Chart with 1331 impedance points. The measurement results of 729 impedance points of the fabricated impedance tuner show that a wide Smith Chart coverage is obtained in the entire band. The RF MEMS phase shifter is designed to cover 0-360 degrees range 10 degree steps at 15 GHz center frequency. The measurement results of the fabricated phase shifter show that the average phase error is 1.7 degrees, the average insertion loss is -3.1 dB, and the average return loss is -19.3 dB for the measured 21 phase states. The phase shifter can also work up to 30 GHz and 40 GHz with average insertion losses of -5 dB and -8 dB, respectively. The designed RF MEMS vector modulator operates in 22.5-27.5 GHz band, and it has 3 amplitude and 8 phase states. The measurement results of the fabricated vector modulator show that the amplitude error is 0.5 dB, the phase error is 4 degrees, and the return loss is -15 dB on average among the 24 measured states at each of 22.5, 25, and 27.5 GHz frequencies.

Microwave and millimeter-wave phase shifters are one of the most important structures of the antenna series that are used in communication and radar applications. They are used to form the main beam of the electronically scanned phase array antennas and generate the appropriate phase values for the antenna elements design while providing electronic beam steering. In this thesis, S-band hybrid 4 bit phase shifter of 22.5&ordm / phase resolution is designed, simulated, fabricated and measured. Bits are separately designed to maintain low phase errors and return loss. In this manner, fabrication and measurements are performed for each bit. These measurements are carried on since each bit reached to its acceptable level of operation. According to the outcomes and acquired knowledge, layout for optimum cascading of 4 bits is developed. Measurement results are compared with simulations and repeatability is tested to observe if it is convenient to use in mass production. Designs and simulations are performed by using ADS2008&reg / .

A heavily filtered fast neutron irradiation system (FNIS) was developed for a variety of applications, including the study of long-term health effects of fast neutrons by evaluating the biological mechanisms of damage in cultured cells and living animals such as rats or mice. This irradiation system includes an exposure cave made with a lead-bismuth alloy, a cave positioning system, a gamma and neutron monitoring system, a sample transfer system, and interchangeable filters. This system was installed in the irradiation cell of the Texas A&M University Nuclear Science Center Reactor (NSCR). By increasing the thickness of the lead-bismuth alloy, the neutron spectra were shifted into lower energies by the scattering interactions of fast neutrons with the alloy. It is possible, therefore, by changing the alloy thickness, to produce distinctly different dose weighted neutron spectra inside the exposure cave of the FNIS. The calculated neutron spectra showed close agreement with the results of activation foil measurements, unfolded by SAND-II close to the cell window. However, there was a considerable less agreement for locations far away from the cell window. Even though the magnitude of values such as neutron flux and tissue kerma rates in air differed, the weighted average neutron energies showed close agreement between the MCNP and SAND-II since the normalized neutron spectra were in a good agreement each other. A paired ion chamber system was constructed, one with a tissue equivalent plastic (A-150) and propane gas for total dose monitoring, and another with graphite and argon for photon dose monitoring. Using the pair of detectors, the neutron to gamma ratio can be inferred. With the 20 cm-thick FNIS, the absorbed dose rates of neutrons measured with the paired ion chamber method and calculated with the SAND-II results were 13.7 ?? 0.02 Gy/min and 15.5 Gy/min, respectively. The absorbed dose rate of photons and the gamma contribution to total dose were 6.7??10-1 ?? 1.3??10-1 Gy/min and 4.7%, respectively. However, the estimated gamma contribution to total dose varied between 3.6 % to 6.6 % as the assumed neutron sensitivity to the graphite detector was changed from 0.01 to 0.03.

Syftet med denna studie var att visa vilka konsekvenser valet av en viss detaljnivå får vid simuleringen av ett system bestående av mjukvara, hårdvara och mekaniska komponenter. Till detta syfte ställdes två frågeställningar “Vad blir konsekvenserna av att lägga sig på en viss detaljnivå vid simulering av ett system bestående av mjukvara, hårdvara och mekaniska komponenter?” och “Hur påverkar detaljnivån när en simulering av ett system bestående av mjukvara, hårdvara och mekaniska komponenter ska verifieras och valideras?”. För att genomföra denna studie och uppnå syftet användes en vanligt förekommande metod för att utveckla simuleringsmodeller. Studien visade på att detaljnivån påverkar vilken information en modell kräver för att konstrueras och vilket användningsområde en modell har. Resultaten tyder på att informationen som finns tillgänglig om det system som en modell ska utvecklas för helt eller delvis begränsar vilken detaljnivå som modellen kan utvecklas på. Studien har begränsat undersökningen till en typ av växelspak och de två modeller som utvecklades ligger på en hög detaljnivå. Examensarbetet har även inte undersökt utvecklingen av modeller, enbart färdiga modeller. / The purpose of this study was to show what consequences a particular level of detail has on the simulation of a system consisting of software, hardware and mechanical components. In order to fulfil this purpose, the following questions were asked: “What are the consequences of using a certain level of detail in a simulation of a system containing software, hardware, and mechanical components?” and “How does the level of detail affect when a simulation of a system containing software, hardware, and mechanical components is verified and validated?”. To carry out this study, a common method for developing simulation models was used. The study showed that the level of detail will affect what information a model requires to be constructed and which uses a model has at that level of detail. The results suggest that the available information about the system that a model is developed for partially restricts the level of detail the model can have. The study is limited to a single type of shifter and all models have been developed at a high level of detail. The study also did not examine the development of models, and only studied finished models.

This thesis is based on promising computing paradigm of reversible logic which generates unique outputs out of the inputs and. Reversible logic circuits maintain one-to-one mapping inside of the inputs and the outputs. Compared to the traditional irreversible computation, reversible logic circuit has the advantage that it successfully avoids the information loss during computations. Also, reversible logic is useful to design ultra-low-power nanocomputing circuits, circuits for quantum computing, and the nanocircuits that are testable in nature. Reversible computing circuits require the ancilla inputs and the garbage outputs. Ancilla input is the constant input in reversible circuits. Garbage output is the output for maintaining the reversibility of the reversible logic but is not any of the primary inputs nor a useful bit. An efficient reversible circuit will have the minimal number of garbage and ancilla bits. Barrel shifter is one of main computing systems having applications in high speed digital signal processing, oating-point arithmetic, FPGA, and Center Processing Unit (CPU). It can operate the function of shifting or rotation for multiple bits in only one clock cycle. The goal of this thesis is to design barrel shifters based on the reversible computing that are optimized in terms of the number of ancilla and garbage bits. In order to achieve this goal, a new Super Conservative Reversible Logic Gate (SCRL gate) has been used. The SCRL gate has 1 control input depending on the value of which it can swap any two n-1 data inputs. We proved that the SCRL gate is superior to the existing conservative reversible Fredkin gate. This thesis develops 5 design methodologies for reversible barrel shifters using SCRL gates that are primarily optimized with the criteria of the number of ancilla and garbage bits. The five proposed methodologies consist of reversible right rotator, reversible logical right shifter, reversible arithmetic right shifter, reversible universal right shifter and reversible universal bidirectional shifter. The proposed reversible barrel shifter design is compared with the existing works in literature and have shown improvement ranging from 8.5% to 92% by the number of garbage and ancilla bits. The SCRL gate and design methodologies of reversible barrel shifter are mapped in Quantum Dot Cellular Automata (QCA) computing. It is illustrated that the SCRL-based designs of reversible barrel shifters have less QCA cost (cost in terms of number of inverters and majority voters) compared to the Fredkin gate- based designs of reversible barrel shifters.

L’objectif de ces travaux de recherche est la conception en technologie intégrée d’une nouvelle topologie de ligne de transmission accordable afin de réaliser des déphaseurs en bande millimétrique. Cette topologie nommée TS-CPW (pour « Tunable Slow wave CoPlanar Waveguide ») utilise d’une part le phénomène d’ondes lentes qui permet de miniaturiser longitudinalement la ligne de transmission et offre un facteur de qualité plus élevé qu’en technologie microruban intégrée, et d’autre part une approche de type MEMS (Micro Electro Mechanical system) afin obtenir l’accordabilité de la ligne avec une figure de mérite élevée comparativement à une approche de type varactor. Dans un premier temps, la topologie et la conception d’une ligne TS-CPW basée sur des simulations électromagnétiques sont présentées en technologie BiCMOS. Dans un second temps, toujours sur la base de TS-CPWs, des déphaseurs présentant 3-bit de résolution, avec différentes valeurs de déphasage total (de 157.5° et 315°), ont été développés à une fréquence de fonctionnement égale à 60 GHz. Les TS-CPWs et les déphaseurs ont été réalisés avec la technologie BiCMOS 0.25 µm de l’institut IHP en Allemagne, puis mesurés à l’aide d’un analyseur de réseau à IHP et à l’IMEP-LaHc. / This work focuses on the design of millimeter-wave phase shifters based on a new topology of tunable transmission lines named Tunable Slow wave CoPlanar Waveguide (TS-CPW). TS-CPW uses, on one side, the slow wave phenomenon in order to miniaturize longitudinally the transmission line and to show a better quality factor than its integrated microstrip transmission line counterpart and, on the other side, the MEMS approach to achieve tunability of the transmission line with a good figure-of-merit. First, the topology, the design and the electromagnetic simulations of the TS-CPW based on MEMS (Micro Electro Mechanical system) are presented in a BiCMOS technology. Next, phase shifters with 3-bit of resolution based on TS-CPWs are developed at 60 GHz with two different values of total phase shift (157.5° and 315°). These TS-CPWs and phase shifters were fabricated in IHP’s 0.25 µm BiCMOS technology and measured on the vector network analyzers of IHP and IMEP-LaHC.

The capacity of optical communications networks continues to grow unabated. Applications for streaming video, social networking and cloud computing, are driving exponential growth of the traffic carried over the world’s ICT networks, which has been sustained thus far through the proliferation of datacenters and efficient, effective use of existing optical fibre. To meet increasing capacity demands requires increasingly sophisticated modulation formats and spectral management to achieve effective use of the available spectrum provided by an optical fibre. Moreover, the technology developed for optical communications is finding broader application to other sectors such as data centres, 5&6 G wireless; lidar and radar. Ultimately, some essential signal processing functions must occur at speeds beyond purely electronic means even when accounting for anticipated technological development. The option is to perform signal processing in the optical domain. Optical signal processors are fundamentally analog and linear in nature. To provide high performance, an analogue processor must be well controlled in a way analogous to the numerous and sophisticated controllers employed by the process industry. Consequently, a further extension of control to deeper levels within the physical layer reaching the optical layer will be necessary. For example, current reconfigurable optical add-drop multiplexers are coloured and directional and the wavelength division multiplexing channel grid, transponders modulation format, and the routing are all fixed. Through optimization of the interface between the physical components, sensors, and processors elastic optical network technology can be achieved by employing colour-, direction-, contention-, grid-less, filter-, gap-less reconfigurable optical add-drop multiplexers, flexible channels centre frequencies and width, flexible sub-carriers in super-channels, flexible modulation formats and forward error control coding transponders, and impairment-aware wavelength routing and spectral assignment. The aim of this thesis is to advance the state-of-the-art in photonic circuits and subsystems via proposing new architecture; study of the feasibility of photonic integration and, proof of concept implementations using available resources. The goal is to introduce new architectural concepts that make effective use of physical components and/or optical processors with reduced energy consumption, reduced footprint and offer speed beyond all-electronic implementations. The thesis presents four case studies based on one or more published papers and supplementary material that advance the goal of the thesis. The first study presents a coherent electro-optic circuit architecture that generates N spatially distinct phase-correlated harmonically related carriers using a generalized Mach-Zehnder Interferometer with its N×1 combiner replaced by an N×N optical Discrete Fourier Transform. The architecture subsumes all Mach-Zehnder Interferometer-based architectures in the prior art given an appropriate selection of output port(s) and dimension N, although the principal application envisaged is phase-correlated subcarrier generation for next-generation optical transmission systems. The theoretical prediction is then verified experimentally using laboratory available photonic integrated circuit fabricated for other applications. Later on, a novel extension of the circuit architecture is introduced by replacing the optical Discrete Fourier Transform network using the combination of a properly chosen phase shifter and single MMI coupler. The second study proposes two novel architectures for an on-chip ultra-high-resolution panoramic spectrometer and presents their design, analysis, integration feasibility, and verification by simulation. The target application is to monitor the power of a wavelength division multiplexed signals in both fixed and flex grid over entire C-band with minimum scan time and better than 1 GHz frequency accuracy. The two architectures combine in synchrony a scanning comb filter stage and channelized coarse filter. The fine filtering is obtained using a ring resonator while the coarse filtering is obtained using an arrayed waveguide grating with appropriate configuration. The fully coherent first architecture is optimised for compactness but relies on a repeatable fabrication processes to match the optical path lengths between a Mach-Zehnder interferometer and a multiple input arrayed waveguide grating. The second architecture is less compact than the first but is robust to fabrication tolerances as it does not require the path length matching. The third study proposes a new circuit architecture for single sideband modulation or frequency conversion which employs a cascade Mach-Zehnder modulator architecture departing from the orthodox dual parallel solution. The theoretical analysis shows that the circuit has 3-dB optical and 3-dB electrical advantage over the orthodox solution. The 3-dB electrical advantage increases the linear operating range of Mach-Zehnder modulator before RF amplifier saturation. An experimental verification of the proposed architecture is provided using an available photonic integrated circuit. The proposed circuit can also perform complex modulation. An alternative implementation based on polarization modulators is also described. The fourth study presents the theoretical modelling of a photonic generation of broadband radio frequency phase shifter. The proposed phase shifter can generate any phase without bound: the complex transmission of the phase shifter follows a trajectory that rotates on a unit circle and may encircle the origin any number of times in either direction, which has great utility in the tuning of RF-photonic systems. The proposed concept is then verified experimentally using off the shelf low frequency electronic components.