Design of hHigh-power sub-THz oscillators

Abstract

This dissertation reports the analysis and design of fundamental and push-push oscillators operating within sub-THz (sub-Terahertz) frequency region. Having to overcome the challenges due to transistor's parasitic capacitance, limited transistor power and lossy passive structure, the output power from a single sub-THz oscillator is very limited. The reported state-of-the-art high-power sub-THz oscillators generally rely on power combining method, which combines the output power of several oscillators to increase the overall oscillator output power. This dissertation focusses on the development of a single sub-THz oscillator in terms of output power and DC-to-RF efficiency, by proposing several oscillator topologies which are suitable to overcome the limiting factors in sub-THz oscillator design. First, study regarding the effective parasitic capacitance of several sub-THz oscillator topologies and the maximum power generated by an active device are presented. Based on this study, a high-power fundamental oscillator topology is proposed. This study is then extended to a push-push oscillator design, which requires optimum performance at both fundamental and 2nd harmonic frequencies in order to maximize the 2nd harmonic power generation. Based on this study, a high-power push-push oscillator topology is then proposed. Finally, two push-push oscillator topologies are proposed, focusing mainly on the parasitic capacitance reduction of push-push oscillators, which allows the proposed topologies to adopt large transistor size, increases the generated output power.