Modern communication systems have increased the need for creative antenna solutions and low-profile circuit configurations that can offer high-quality performance at a low cost. The microwave and millimeter-wave frequency ranges have shown much promise allowing for increased data transmission rates while also offering smaller and compact designs. Specific applications for these wireless systems include radar, biomedical sensors, phased arrays, and communication devices. Planar antennas and circuits are generally well adopted for these applications due to their low profile and ease of fabrication. However, classic feeding techniques for planar structures can be problematic. Losses can also be observed in these conventional feeding schemes due to unwanted surface wave (SW) excitation. This can lead to reduced antenna and circuit efficiencies, and thus, diminished system performance. It is shown in this thesis that by the use of planar SW sources, or surface-wave launchers (SWLs), innovative and efficient antennas and feed systems are possible. Theoretical analysis and experimental verification for these SWLs are initially presented. New topologies and array configurations are also examined for directive beam steering at end-fire and at broadside. Additionally, studied structures include novel surface-wave antennas (SWAs) and leaky-wave antennas (LWAs) for 3-D beam pattern control in the far-field. A comprehensive design strategy is also examined which describes the implementation of these planar antennas using SWLs. This design strategy is based on a full-wave analysis of the modes that can be supported by the planar structures which include various planar-periodic metallic strip configurations and partially reflecting surfaces (PRSs) or screens. With appropriate conditions SWs can also be bound and guided for field channeling and power routing. For instance, novel planar metallic SW lenses and guidance structures are developed. Demonstrated applications include couplers, transition sections, as well as new planar circuits for power dividing/combining. To the author's knowledge, similar techniques have not been previously studied in the literature which allow for such controlled SW propagation and radiation. This way, SWs, which are normally considered an unwanted effect are used here to advantage. / Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2013-09-30 08:29:04.107

Transgenic lines of sugarcane with increased total sugar content have been obtained in previous work in our lab, through the introduction of a sucrose isomerase (SI) gene designed vacuole-targeting of the SI gene product. Some of the resulting transgenic lines accumulate the high value sugar isomaltulose (IM) without decrease in stored sucrose content. Other lines show enhanced sucrose content with low levels of IM in mature storage tissues. Under containment glasshouse conditions, these “SugarBooster™” lines have shown up to two-fold increase in the total sugar concentration in the harvested juice. This remarkable step above the former ceiling in stored sugar concentration may permit new insights into the mechanisms by which plants regulate sugar accumulation, a pivotal question in plant biology. Studies conducted in this thesis are a part of the effort to understand the underlying mechanisms. Experiments were focused on the regulation of SI and endogenous genes related to sucrose metabolism, as revealed by transcript levels. Enzyme activity was also tested for sucrose phosphate synthase (SPS), a key enzyme in plant sucrose biosynthesis. Initially, the relationship between IM content and SI transcript level was analyzed. Real-time quantitative polymerase chain reaction (RT-qPCR) successfully detected SI gene transcripts in internodes of different maturities in SugarBooster™ lines, but no correlation was found between the transcript level and IM content. In contrast, northern blotting to distinguish full-length SI mRNA from degraded transcripts revealed a positive relationship between IM content and functional transcripts of SI. The results imply that stabilization of SI mRNA is important for high IM content but that high sucrose accumulation accompanied by low IM involves other mechanisms. Therefore, transcript levels of several key genes in sucrose metabolism were analyzed in internodes at various developmental stages in SugarBooster™ iv and control lines. These genes encode sucrose phosphate synthase (SPS), sucrose synthase (SuSy), soluble acid invertase (SAI), neutral invertase (NI), cell wall invertase (CWI), a putative sugar transporter type 2a (Type2a) and sucrose transporter type 6 (Type6). Sucrose content was negatively correlated to the transcript levels of SAI, but there were no significant correlations between sugar content and mRNA levels of other tested enzymes across all developmental stages. However, interesting transcript patterns that might contribute to high sucrose accumulation were observed in some lines. Examples from different lines include: SuSy transcripts increased in immature internodes but decreased in mature ones; NI expression decreased in mature internodes and sugar transporters increased in some cases. Further analysis was undertaken on transcript regulation of five SPS families, as SPS is the rate-limiting enzyme for sucrose biosynthesis in some plant systems. As recently reported from a CSIRO analysis of sugarcane progeny segregating for sucrose content, transcripts of SPS family 2 predominated in the stem for both SugarBooster™ and control lines. Transcripts of SPS families 3 and 4 were less abundant and families 1 and 5 were rare. More abundant mRNAs of SPS families 2, 3 and 4 indicate that they play an important role in sucrose accumulation in the stem. However, none of the mRNA levels of the five families had a significant correlation to the SPS enzyme activity or to the sucrose content measured in corresponding tissues. In contrast, SPS enzyme activity was found positively correlated to sucrose content. It revealed that regulation of SPS in sugarcane is mainly at the level of enzyme activity. These studies have been constrained by the availability of experimental material in early vegetative generations of SugarBooster™ lines under containment glasshouse conditions. As the opportunity emerges for more material from approved field trials, it will be important to identify the most stable lines under field conditions, for further studies on metabolites, carbon partitioning and enzyme activity to fill the gap in understanding between regulation at transcript level and the SugarBooster™ phenotypes.

This thesis explores means of mitigating the effects of silicon variation on SRAM by means of circuit techniques. This thesis also explores novel read and write techniques for MRAM that support a non-destructive read operation and power-saving write operations in the face of device and silicon variation. First, this thesis proposes the use of a cross-coupled bit line BL biasing scheme that retains an SRAM's fast access speed while reducing the read-access failures in the presence of Vt variation, without excessively increasing the SRAM cell size. It is shown, by extensive Monte-Carlo simulations using 22-nm predictive CMOS models, that the proposed scheme reduces the cell area by 6.5% compared to the conventional BL biasing schemes also analyzed. Second, this thesis proposes a 10T SRAM cell that supports lower voltage operation, achieves lower static power dissipation, and is similar in area to the 6T SRAM cell when the 3-sigma variation of Vt exceeds 40% of nominal Vt. The 10T cell achieves improved write functionality, in comparison to the 6T cell, by preemptively turning off the cell's power supply to the side of the cell that is being pulled low, while not disturbing any unselected cells. Write access time is not affected, as the positive-feedback required to quickly regenerate CMOS voltage levels remains intact. Finally, this thesis proposes a negative-resistance read scheme and write scheme for spin-torque-transfer (STT) MRAM. A negative resistance shunting an STT-MRAM cell guarantees a non-destructive read operation, and saves power during write operations compared with a conventional scheme. Measurements confirm an 7ns non-destructive read access time without the use of a typical sense amplifier and an average write power savings of 10.5% for a 16Kb STT-MRAM fabricated in 0.13um CMOS using a CoFeB/MgO/CoFeB MTJ.

This thesis explores means of mitigating the effects of silicon variation on SRAM by means of circuit techniques. This thesis also explores novel read and write techniques for MRAM that support a non-destructive read operation and power-saving write operations in the face of device and silicon variation. First, this thesis proposes the use of a cross-coupled bit line BL biasing scheme that retains an SRAM's fast access speed while reducing the read-access failures in the presence of Vt variation, without excessively increasing the SRAM cell size. It is shown, by extensive Monte-Carlo simulations using 22-nm predictive CMOS models, that the proposed scheme reduces the cell area by 6.5% compared to the conventional BL biasing schemes also analyzed. Second, this thesis proposes a 10T SRAM cell that supports lower voltage operation, achieves lower static power dissipation, and is similar in area to the 6T SRAM cell when the 3-sigma variation of Vt exceeds 40% of nominal Vt. The 10T cell achieves improved write functionality, in comparison to the 6T cell, by preemptively turning off the cell's power supply to the side of the cell that is being pulled low, while not disturbing any unselected cells. Write access time is not affected, as the positive-feedback required to quickly regenerate CMOS voltage levels remains intact. Finally, this thesis proposes a negative-resistance read scheme and write scheme for spin-torque-transfer (STT) MRAM. A negative resistance shunting an STT-MRAM cell guarantees a non-destructive read operation, and saves power during write operations compared with a conventional scheme. Measurements confirm an 7ns non-destructive read access time without the use of a typical sense amplifier and an average write power savings of 10.5% for a 16Kb STT-MRAM fabricated in 0.13um CMOS using a CoFeB/MgO/CoFeB MTJ.

This thesis presents an analysis of photon pairs generated via either spontaneous parametric downconversion or spontaneous four-wave mixing in channel waveguides as well as in microring resonators side-coupled to channel waveguides. The state of photons exiting a particular device is calculated within a general Hamiltonian formalism that simplifies the link between quantum nonlinear optics experiments and classical nonlinear optics experiments. This state contains information regarding photon pair production efficiency as well as modal and spectral correlations between the two photons, characterized by a two-dimensional spectral distribution function called the biphoton wave function. In the limit of a low probability of pair production, photon pair production fficiencies are cast into forms resembling corresponding well-known classical nonlinear optical frequency conversion efficiencies, making it easy to see what plays the role of a classical “seed” field in an un-seeded (quantum) process. This also allows photon pair production efficiencies to be calculated based on the results of classical nonlinear optical experiments. It is further calculated that, unless enerated photons are collected over a very narrow frequency range, their generation efficiency does not scale the same way with device length in a channel waveguide, or resonance quality factor in a microring resonator, as might be expected from the corresponding classical frequency conversion efficiency. Although calculations do not include self- or cross-phase modulation, nor two-photon absorption or free-carrier absorption, it is calculated that their neglect is justified in the low pair production probability limit. Linear (scattering) loss is also neglected, though partially addressed in the final chapter of this thesis. Biphoton wave functions are calculated explicitly, such that their shape and orientation, including approximate analytic expressions for their widths, can easily be determined. This further allows estimation of the suitability of their associated photon pairs for various quantum information processing applications. As an alternative to dispersion engineering a channel waveguide photon pair source, it is calculated that microring resonators can very naturally produce nearly spectrally uncorrelated photon pairs, which behave very much like idealized single-mode photons and are thus useful for applications involving the interference of photons from multiple sources.

This thesis presents an analysis of photon pairs generated via either spontaneous parametric downconversion or spontaneous four-wave mixing in channel waveguides as well as in microring resonators side-coupled to channel waveguides. The state of photons exiting a particular device is calculated within a general Hamiltonian formalism that simplifies the link between quantum nonlinear optics experiments and classical nonlinear optics experiments. This state contains information regarding photon pair production efficiency as well as modal and spectral correlations between the two photons, characterized by a two-dimensional spectral distribution function called the biphoton wave function. In the limit of a low probability of pair production, photon pair production fficiencies are cast into forms resembling corresponding well-known classical nonlinear optical frequency conversion efficiencies, making it easy to see what plays the role of a classical “seed” field in an un-seeded (quantum) process. This also allows photon pair production efficiencies to be calculated based on the results of classical nonlinear optical experiments. It is further calculated that, unless enerated photons are collected over a very narrow frequency range, their generation efficiency does not scale the same way with device length in a channel waveguide, or resonance quality factor in a microring resonator, as might be expected from the corresponding classical frequency conversion efficiency. Although calculations do not include self- or cross-phase modulation, nor two-photon absorption or free-carrier absorption, it is calculated that their neglect is justified in the low pair production probability limit. Linear (scattering) loss is also neglected, though partially addressed in the final chapter of this thesis. Biphoton wave functions are calculated explicitly, such that their shape and orientation, including approximate analytic expressions for their widths, can easily be determined. This further allows estimation of the suitability of their associated photon pairs for various quantum information processing applications. As an alternative to dispersion engineering a channel waveguide photon pair source, it is calculated that microring resonators can very naturally produce nearly spectrally uncorrelated photon pairs, which behave very much like idealized single-mode photons and are thus useful for applications involving the interference of photons from multiple sources.

In this dissertation the proper determination and allowable signs of the effective parameters of metamaterial structures will be examined. First, a method that was commonly used to determine the presence of a negative index of refraction will be discussed. It will be shown that this method, which relies on the appearance of transmission peaks in the region where the real parts of the effective permittivity and permeability are expected to be negative, does not provide sufficient evidence that a negative index exists. Two alternate methods will then be presented that can be used to properly determine the sign of the index. Then, the form of the index in media that exhibit backward wave propagation will be examined from a purely three dimensional wave propagation point of view. It will be shown that in an isotropic medium backward wave propagation requires that the index be negative and in an anisotropic medium it requires that the index be negative along at least one of the three principal axes. In short, the necessary and sufficient condition for the negative index of refraction is the existence of the backward wave. Next, a technique commonly used to retrieve the effective parameters in metamaterials from transmission and reflection data will be considered. It will be shown that this retrieval technique can lead to unphysical claims that the imaginary parts of the effective permittivity or permeability can be negative even though the medium remains passive. By comparing the effective parameters obtained analytically and from the retrieval technique it will be shown that these unphysical claims are the result of error in the numerical simulations. The concepts of causality and analyticity will also be discussed by considering the Lorentzian model and it will be shown that this model does not allow the imaginary parts of the permittivity or permeability to be negative in the metamaterials consisting of split ring resonators and split wires.

A search for diphoton events with large missing transverse energy is conducted using 3.1 pb^{-1} of integrated luminosity of proton-proton collisions at center of mass energy \sqrt{s}=7 TeV. The data were collected with the ATLAS detector at the CERN Large Hadron Collider during the period from March 30, 2010 until August 30, 2010. No excess of such events is observed above the Standard Model background prediction. This result is interpreted in the context of a gravity mediated One Universal Extra Dimension model with \Lambda R=20, N=6 and M_{D}=5 TeV, where \Lambda is the cutoff scale, N is the number of large extra dimensions and M_{D} is the Planck scale in the higher dimensional theory. The compactification radius of the Universal Extra Dimension, R, is excluded for values of 1/R < 728 GeV at 95\% CL, providing the most stringent limit on this model at the time of publication.

This thesis focuses on the interplay of the spin-orbit coupling, the electronic correlations and the bandwidth energy scales, along with the lattice distortions seen in perovskite iridates. In particular, we study the magnetic phases in these materials and the insulator to metal transition that occurs as the dimensionality of the system is changed. Motivated by the novel magnetic phases seen in the Sr2IrO4 system, we study the band structures of three materials in the Sr(n+1)Ir(n)O(3n+1) Ruddlesden-Popper series by use of a tight-binding model. From the effect of spin-orbit coupling, we see that the relevant bands near the Fermi energy are indeed made of effective J=1/2 states. This spin-orbit separation of the bands creates effectively smaller bandwidth which can then be split via magnetic ordering driven by electronic correlations. By the use of a self-consistent mean-field theory, we derive the ordering for each of the three materials studied and show that the nature of the magnetic ordering is highly dependent on the lattice structure. The ordering in the bilayer Sr3Ir2O7, which has been a topic of debate in recent experimental studies, is understood within the current approach to be a collinear antiferromagnetic order, in agreement with the latest results. Given that the iridate systems have large spin-orbit coupling, and that the topic of topological insulators has become a very popular subject of research, we discuss the proximity of the perovskite iridates to topological insulators. Since the SrIrO3 material displays a semimetal structure with nodal dispersion near the Fermi level, we looked at an extra term in the Hamiltonian that could lift the nodal lines and turn the system into an insulator. Further studies of the parity eigenvalues of the bands at each time reversal invariant momentum point confirms that for a range of this extra term, a topological phase can be achieved. A discussion on material realization of such a phase is also given where we suggest that a Sr2IrRhO6 superstructure might be a good candidate to achieve this state.

In this dissertation the proper determination and allowable signs of the effective parameters of metamaterial structures will be examined. First, a method that was commonly used to determine the presence of a negative index of refraction will be discussed. It will be shown that this method, which relies on the appearance of transmission peaks in the region where the real parts of the effective permittivity and permeability are expected to be negative, does not provide sufficient evidence that a negative index exists. Two alternate methods will then be presented that can be used to properly determine the sign of the index. Then, the form of the index in media that exhibit backward wave propagation will be examined from a purely three dimensional wave propagation point of view. It will be shown that in an isotropic medium backward wave propagation requires that the index be negative and in an anisotropic medium it requires that the index be negative along at least one of the three principal axes. In short, the necessary and sufficient condition for the negative index of refraction is the existence of the backward wave. Next, a technique commonly used to retrieve the effective parameters in metamaterials from transmission and reflection data will be considered. It will be shown that this retrieval technique can lead to unphysical claims that the imaginary parts of the effective permittivity or permeability can be negative even though the medium remains passive. By comparing the effective parameters obtained analytically and from the retrieval technique it will be shown that these unphysical claims are the result of error in the numerical simulations. The concepts of causality and analyticity will also be discussed by considering the Lorentzian model and it will be shown that this model does not allow the imaginary parts of the permittivity or permeability to be negative in the metamaterials consisting of split ring resonators and split wires.