太赫茲(THz)頻段(0.3-3 THz)近幾年在新興應用如影像、超高速無線通訊、感測和分子光譜學領域快速發展。隨著先進CMOS製程持續發展，低成本和高集成度的太赫茲系統已經可以成為未來工業應用以及消費端產品。然而，在這些新興應用中，由於CMOS製程中電晶體較低的崩潰電壓、高頻下電晶體模型的不準確性、電晶體的非線性模型以及電晶體最高操作頻率f_max的限制，實現一個高輸出功率和低相位雜訊的太赫茲訊號源還是一個困難的課題。為了解決此問題，目前實現的方法分為諧波震盪器和倍頻器串列。諧波震盪器為利用電晶體的非線性度來產生高於f_max的高次諧波訊號，而震盪器本身是操作在基頻訊號。此論文採用倍頻器為基底的諧波震盪器，探討兩個基於四倍頻操作的太赫茲震盪器，利用基頻的I/Q訊號透過四倍頻器的濾波特性將低倍諧波訊號濾掉，在輸出端產生四倍頻THz訊號。第一個work為實作在28nm，操作在560-GHz的四倍頻震盪器，震盪器架構選擇為Colpitts oscilliator，因為寄生電容較小，此架構震盪器可以操作在更高頻。基頻為140-GHz的四相位Colpitts震盪器和四倍頻器，輸出達到-16.3 dBm的輸出功率，並經由on-chip antenna將訊號輸出。第二個work是實作在90nm的一個注入鎖定四倍頻震盪器，由一個四相位注入鎖定的84-GHz Series-coupled QVCO、3級放大器以及四倍頻器所組成，輸出端為336-GHz的四倍頻訊號。注入鎖定的輸入訊號源可進一步實作一個on-chip的PLL，可以使輸出訊號的相位雜訊更低。

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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