| Summary: | 碩士 === 國立清華大學 === 電機工程學系所 === 107 === Terahertz (THz) band (0.3-3 THz) has gained much more interest in the past few years for emerging applications such as imaging, ultra-high speed wireless communication, sensing and molecular spectroscopy. With CMOS technology keeps scaling down, low cost and high integration THz system is available for future industrial applications and consumer products. However, in these applications, realizing a high output power and low noise signal source still remains challenging due to low breakdown voltage, transistor model inaccuracy, nonlinearity modeling for maximum harmonic output power and insufficient transistor f_max limitation in CMOS technology. To overcome these difficulties, two common approaches are utilized in generating THz frequency signal: harmonic VCO and multiplier chain. Harmonic VCO method utilized device nonlinearity to generate higher-order harmonic signal beyond fmax with oscillator operating at fundamental frequency below transistor frequency limitation, which is achievable in advanced CMOS technology. This thesis proposed two works based on quadruple-push technique with a fundamental quadrature VCO and two cascaded frequency doublers. By utilizing the nature of the quadruple-push harmonic generator with I/Q fundamental input, only the fourth harmonic THz signal is present at the output while the lower harmonic signals (fo, 2fo, 3fo) are rejected due to out of phase signal. The first work focus on 560-GHz output frequency, including a 140-GHz quadrature Colpitts VCO and two cascaded frequency doublers which achieved -16.3 dBm peak output power and 15.6-GHz tuning range. The second work is an injection-locked quadruple-push 336-GHz harmonic VCO, including an injection-locked Series-QVCO, 3-stage cascode amplifier and quadruple-push harmonic generator, which could be further scaled to a 2x2 THz source array injection-locked by an on-chip PLL for frequency synchronization between array elements.
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