A model relating the gain of a Nd³⁺ -glass laser amplifier to its input pumping energy is developed in this thesis. This model, which is based on the Nd³⁺ rate equations, is tested experimentally, using a giant pulse as the input to the amplifier. The results of these experiments conform well to the model. / Thesis / Master of Science (MSc)

Demand for capable and reliable semiconductor and fabrication technology for high temperature and power electronics applications has been increasing in recent years. Silicon Carbide (SiC), as a wide bandgap compound semiconductor, demonstrates superior characteristics such as high thermal conductivity, high breakdown voltage, and long-lasting reliable operation at elevated temperature. SiC-based circuits and systems are capable to offer significant performance enhancements to various applications. Integrated power management units and conversion modules in HEVs, integrated sensors for aircraft engines, development of small-sized portable power generators are among many applications that require reliable circuits with long-lasting functional lifetime. Nevertheless, there are numerous challenges associated with the design and fabrication of SiC-based circuits. The aim of this research is to practically design and implement novel operational amplifiers (opamps) based on Vertical Channel 4H-SiC JFET (SiC JFET) that can be utilized as sub-circuits of integrated SiC JFET-based circuits and systems. Recently, SiC power JFET-based power management units were developed that deploy non-SiC JFET-based circuits for analog signal processing, driving, and control, because all SiC JFET-based circuits were not available for full integration. However, utilizing SiC JFET for analog design (in order to close the mentioned gap) exhibits significant design challenges, even at room temperature. These fundamental challenges are low intrinsic gain, the requirement to limit the gate to source voltage range, and restrictions on utilizing channel length as a design parameter due to fabrication complexity. These challenges must be successfully overcome at room temperature, before moving towards high temperature SiC JFET-based analog design. The main objective of this dissertation is to establish a design base, overcome the challenges, demonstrate the feasibility, and present all SiC JFET-based opamps that are designed for gain, CMRR, and overall performance. Before attempting to design, both Enhancement and Depletion Mode SiC JFETs are characterized, analyzed, and modeled for simulation. Unique and reliable opamp configurations are presented that take design requirements into account, use threshold voltage instead of channel length as a design parameter, and employ gain enhancement techniques while obtaining maximum possible bandwidth. The final opamps are fabricated and tested and the results show that the objective is accomplished.

No description available.

No description available.

No description available.

No description available.

Currently in the marketplace, one of the important goals is to improve quality, and reliability. There is great interest in the engineering community to develop a field calibration technique concerning piezoelectric pressure sensor to reduce cost and improve reliability. This paper summarizes the algorithm used to characterize and develop a model for a piezoelectric pressure transducer. The basic concept of the method is to excite the sensor using an electric force to capture the signature characteristic of the pressure transducer. This document presents the frequency curve fitted model based on the high frequency excitation of the piezoelectric pressure transducer. It also presents the time domain model of the sensor. The time domain response of the frequency curve fitted model obtained in parallel with the frequency response of the time domain model and the comparison results are discussed. Moreover, the relation between model parameters and sensitivity extensively is investigated. In order to detect damage and monitor the condition of the sensor on line the resonance frequency comparison method is presented. The relationship between sensitivity and the resonance frequency characteristic of the sensor extensively is investigated. The method of resonance monitoring greatly reduces the cost of hardware. This work concludes with a software implementation of the signature comparison of the sensor based on a study of the experimental data. The software would be implemented in the control system. / Master of Science

With the rapid expansion of wireless communication services, ultra-miniature, low cost RF microsystems operating at higher carrier frequencies (e.g. 5-6 GHz) are in demand for various applications. Such applications include networked wireless sensor nodes and wireless local area data networks (WLANs). Integrated microstrip antennas coupled directly to the RF electronics, offer potential advantages of low cost, reduced parasitics, simplified assembly and design flexibility compared to systems based on discrete antennas. However, the size of such antennas is governed by physical laws, and cannot be arbitrarily reduced. The critical patch antenna dimension at resonance needs to be ~ λ_g/2 (where λ_g is the guided wavelength given by λ_g=λ₀/√(𝜖_r) . Several methods are available to reduce the physical size of the antenna to enable on-chip integration. A high dielectric constant substrate reduces the guided wavelength. Grounding one edge of the microstrip patch enables the resonant antenna length to be further reduced to ~ λ_g/4. However, these techniques result in degraded antenna efficiency and bandwidth. Nonetheless, such antennas still have potential for use in low power/short range applications. In this work, "electrically small" (small with respect to λ₀) square-shaped microstrip patch antennas, grounded on one edge by shorting posts, have been investigated. The antenna input impedance depends on the feed position; by adjusting the feed point, the antenna can be tuned to match a 50 Ω or other system impedance. The antennas were designed on a GaAs substrate, with a high dielectric constant of 12.9. The size of the patch antenna is further reduced by utilizing shorted through substrate vias along one edge. The size of the antenna is about 4.2mm × 4.2mm, which is ~1/13 of λ₀ at ~5.6GHz. The antennas are practical for integration on chip. Due to the size reduction, the simulated peak gain of the antenna is only −10.2 dB (~3.2% radiation efficiency). However, this may be acceptable for short-range wireless communications and distributed sensor network applications. Based on the above approach, integrated GaAs "chip-scale" antennas with matching power amplifiers have been designed and fabricated. Class A tuned MESFET power amplifiers (PAs) were designed with outputs directly matched to the antenna feed point. The antenna is fabricated on the backside of the chip through backside patterning; the PA feeds the antenna through a backside via. The structure is then mounted such that the antenna faces up, and is compatible with flip-chip technology. The measurement of a 50 Ω passive (no PA) antenna indicates a gain of -12.7dB on boresight at 5.64 GHz, consistent with the antenna size reduction. The measurement of one active antenna (50 Ω system) shows a gain of -4.3dB on boresight at 5.80 GHz. The other version of active antenna (22.5 Ω system) shows a gain of −2.9 dBi on boresight at 5.725 GHz. The active circuitry (PA) contributes an average of ~9 dB gain in the active antenna, reasonable close to the designed PA gain of 12.7dB. The feasibility of direct integration of a PA with an on-chip antenna in a commercial GaAs process at RF frequencies was successfully demonstrated. / Master of Science

Efficient generation of 1.5 um wavelength light has applications for ranging and remote sensing while being in the "eye safe" region of the optical spectrum. Diamond Raman lasers are excellent candidates for light sources at these wavelengths due to the excellent optical and mechanical properties of diamond as a laser material. This thesis describes the design and build of a MOPA fiber laser system in the CW regime as a pump for a Diamond Raman laser along with a design for operating it in the pulsed regime as well. The CW fiber laser was tested up to 200 W average power and characterized for each stage of the MOPA architecture. The third and final amplifier stage uses an extra large mode area(XLMA) fiber for decreasing irradiance of the signal with in the fiber and thus mitigating the unwanted nonlinear effects at the output when the system will be pulsed. Engineering designs will be presented for fiberized components that reduce the amount of passive fiber in the system overall. The process of putting end caps on the fiber facets will also be described. The multimode nature of the XLMA fiber required mode mixing elements to obtain a more uniform flat top beam profile. Characterization of the mode mixing fiber will be presented along with the output profile improvement.

Cellular radio communication involves wireless transmission and reception of signals at radio frequencies (RF). Base stations house equipment critical to the transmission and reception of signals. Power amplifier (PA) is a crucial element in base station assembly. PAs are expensive, take up space and dissipate heat. Of all the elements in the base station, it is difficult to design and operate a power amplifier. New designs of power amplifiers are constantly tested. One of the most important components required to perform this test successfully is a circuit simulator model of an entire communication system that generates a standard test signal. Standard test signals 524,288 data points in length require 1080 hours to complete one test of a PA model. In order to reduce the time taken to complete one test, a 'simulated test signal,' was generated. The objective of this study is to develop an algorithm to generate this 'simulated' test signal such that its characteristics match that of the 'standard' test signal.