Digitized by Kansas Correctional Industries

Thesis--Ohio State University. / Includes bibliographical references. Available online via OhioLINK's ETD Center

In this thesis, S-bend waveguides and ring resonant filters with multimode interference (MMI) couplers have been designed and fabricated. The single-ring filters are designed to have free spectral ranges ( FSR's) of 33.3GHz, 40GHz and 50GHz. The FSR's of double-ring filters are 100GHz and 200GHz. The splitting ratios of the 9-

Microstrip ring circuits have been extensively studied in the past three decades. A magnetic-wall model has been commonly used to analyze these circuits. Unlike the conventional magnetic-wall model, a simple transmission-line model, unaffected by boundary conditions, is developed to calculate the frequency modes of ring resonators of any general shape such as annular, square, or meander ring resonators. The new model can be used to extract equivalent lumped element circuits and unloaded Qs for both closed- and open-loop ring resonators. Several new bandpass filter structures, such as enhanced coupling, slow-wave, asymmetric-fed with two transmission zeros, and orthogonal direct-fed, have been proposed. These new proposed filters provide advantages of compact size, low insertion loss, and high selectivity. Also, an analytical technique is used to analyze the performance of the filters. The measured results show good agreement with the simulated results. A compact elliptic-function lowpass filter using microstrip stepped impedance hairpin resonators has been developed. The prototype filters are synthesized from the equivalent circuit model using available element-value tables. The filters are evaluated by experiment and simulation with good agreement. This simple equivalent circuit model provides a useful method to design and understand this type of filters and other relative circuits.Finally, a tunable feedback ring resonator oscillator using a voltage controlled piezoelectric transducer is introduced. The new oscillator is constructed by a ring resonator using a pair of orthogonal feed lines as a feedback structure. The ring resonator with two orthogonal feed lines can suppress odd modes and operate at even modes. A voltage controlled piezoelectric transducer is used to vary the resonant frequency of the ring resonator. This tuned oscillator operating at high oscillation frequency can be used in many wireless and sensor systems.

The present work advances progress on the validation against measurements of linear and nonlinear rotordynamic models for predicting the dynamic shaft response of automotive turbochargers (TCs) supported on floating ring bearings. Waterfall spectra of measured shaft motions at the compressor and turbine ends of a test TC rotor evidences a complex response, showing synchronous (1X) and multiple subsynchronous frequencies along the entire operating speed range (maximum shaft speed ~ 65 krpm). Postprocessing of the raw test data by mathematical software allows filtering the synchronous and subsynchronous vibration components for later comparisons to predicted shaft motions. The static performance of the floating ring bearings is analyzed with in-house software (XLSFRBThermal®), which considers thermal expansion of the shaft and bearing components as well as static loading on the bearing due to lubricant feed pressure. In addition, the program calculates rotordynamic force coefficients for the inner and outer films of the floating ring bearing. The turbocharger Finite Element (FE) structural model for the linear and nonlinear analyses includes lumped masses for the compressor and turbine wheels and the thrust collar. The mass imbalance distribution on the TC rotor is estimated from the test data using a procedure derived from the two-plane balancing method with influence coefficients. The linear model yields predictions of rotor synchronous (1X) response to imbalance and damped eigenvalues. The analysis evidences that the rotor cylindrical-bending mode is unstable at all shaft speeds while the rotor conical model becomes more unstable as lubricant feed pressure decreases. The predicted synchronous (1X) motions agree well with the test data, showing a critical speed at approximately 20 krpm. The linear stability results indicate the existence of three critical speeds occurring at 4, 20 and 50 krpm. The second critical speed corresponds to the rotor cylindrical-bending mode, showing larger amplitudes of motion at the compressor nose than at the turbine end. The third critical speed associated to the rotor first bending modes is well damped. In the nonlinear transient analysis, the nonlinear equations of motion of the system (rotor-FRB) are integrated, and the bearing reaction forces are calculated at each time step in a numerical integration procedure. The model then yields predictions of total motion which is decomposed into synchronous (1X) and subsynchronous motions, amplitudes and frequencies. The nonlinear analysis predicts synchronous (1X) amplitudes that correlate well with the test data at high shaft speeds (> 30 krpm) but underpredicts the imbalance response at low shaft speeds (<30 krpm). The time transient simulations predict multiple frequency subsynchronous motions for shaft speeds ranging from 10 krpm to 55 krpm, with amplitudes and frequencies that are in good agreement with the measurements. Finally, the shaft motion measurements and predictions demonstrate that the turbocharger dynamic response does not depend greatly on the lubricant feed pressure and inlet temperature for the conditions tested.

In this paper, a ring laser design based on tapered waveguide coupler is fabricated and discussed. Using the asymmetric tapered waveguide coupler, two different directional coupling can be realized. Such that, the spatial-hole burning problem in linear laser cavity can be avoided, leading to the possibility of unidirectional traveling laser. In the work, two types of ring laser structures are fabricated and analyzed, in which (1) 90 degrees total reflection mirrors (TIMs) and (2) circular retro-mirrors are defined. Through the current injection on the tapered waveguide coupler, the received spontaneous emissions power at different directions (clockwise and counterclockwise directions) shows a 3dB difference for both type (1) and (2). Two oscillations in ring resonator could give different round-trip loss, indicating the possibility to fabricate unidirectional ring laser.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

No description available.

No description available.

No description available.