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Stimulated Raman Scattering (SRS) is a Coherent Raman microscopy method that has been increasingly employed in recent years for highly-specific, label-free, and high-speed bioimaging. Compared to a similar Coherent Raman method, the so-called Coherent Anti-Stokes Scattering (CARS) microscopy, it exhibits advantages such as the absence of nonresonant background (NRB) and the linearity of the signal intensity on the concentration of molecules of interest. However, SRS can be affected by unwanted background signals that hinder the acquisition of an accurate Raman information. These unwanted signals are generated by parasitic effects that are difficult to suppress in standard SRS setups. Here, I present a frequency-modulation (FM) SRS technique via an Acousto-Optic Tunable ioilter (AOTF), describing its implementation on Vibra Lab setup and assessing its efficiency with imaging results. The FM technique provides a cancellation of the unwanted background signals, maintaining intact the SRS information. It is based on the weak spectral dependence of the parasitic effects as compared to the high spectral specificity of the SRS signal. The proposed scheme presents a few advantages when compared with other solutions presented in the literature. In particular, it doesn't require a complex setup configuration, and it can be used seamlessly in a very broad range of the vibrational spectrum.

This these explores automatic modulation recognition as applied to PCM/FM, SOQPSK- TG and ARTM CPM. It found that the likelihood based approach is intractable. The statistical features of the amplitude, phase and frequency are ineffective at distinguishing these modulation types. A method based on the phase changes between symbols is developed and shows that as long as symbol timing is established, this method can effectively distinguish PCM/FM, SOQPSK-TG and ARTM CPM for signal-to-noise ratios above 30 dB. Another method, the Bianchi-Loubaton- Sirven technique, was able to distinguish PCM/FM and SOQPSK-TG but was unable to distinguish ARTM CPM. A happy byproduct of this classification algorithm is a reasonably accurate estimate of the bit rate. Simulation results show that this classifier works essentially error-free for signal- to-noise ratios above 20 dB and for sufficiently high resolution in the search algorithms required by the maximizations.

The duty cycle control (DCC) modulation scheme for the three-phase dual-active-bridge (3p-DAB) DC-DC converter is a promising three degree-of-freedom modulation scheme which can extend the converter’s soft-switching range and reduce conduction losses under partial loading and wide voltage variations. However, the prior suggested methods to implement DCC in 3p-DABs have drawbacks such as requiring a multi-frequency approximation and offline optimization process or achieving less than optimal efficiency. To overcome these challenges, this research first proposes an optimal DCC modulation strategy (OMS) for the 3p-DAB based on a novel piece-wise time-domain analysis (TDA) and optimization process that obtains the optimal control parameters for minimum RMS phase current. Secondly, this research proposes a novel closed-form minimum current stress optimization (MCSO) DCC scheme based on the theoretical findings of the TDA optimization. The MCSO reduces the transformer phase currents and extends soft-switching operation under partial loading and wide voltage variations. Experimental results via open-loop testing show that the proposed closed-form MCSO DCC scheme has virtually identical efficiency as the OMS, making this the first research to provide a closed-form DCC modulation scheme for a 3p-DAB that achieves efficiency results equivalent to a fully-optimized offline scheme, but without the drawbacks of the offline optimization process. / Thesis / Master of Applied Science (MASc)

<p> The feasibility of using a partial response-encoded single-sideband (SSB) modulated signal for transmission of digital data in a radio system is considered. The principal methods of SSB signal generation and demodulation are examined, and the effects of carrier synchronization are determined. The effect of steady-state carrier phase errors on the error rate of an SSB partial response receiver is analyzed theoretically and by means of computer simulation. The analysis of a decision-directed SSB carrier phase tracking loop is presented and its performance is evaluated using computer simulation. The performance of the SSB partial response system after amplification by means of travelling-wave-tube (TWT) amplifiers is analyzed by using computer simulation. Finally, a comparison of an SSB partial response system and a quadrature partial response system (QPRS) is made.</p> / Thesis / Master of Engineering (MEngr)

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