Electromagnetic waves at millimeter-wave/sub-Terahertz (mm-Wave/sub-THz) frequencies (60 GHz ~ 300 GHz) can interact uniquely with gas molecules, and by detecting the frequency responses of the absorption gas cells, the unique spectral patterns of the gas molecules can be identified and detected with high accuracy. As a result, mm-Wave/sub-THz frequency range has attracted growing interest for rotational spectroscopy for its great potential in environment safety, homeland security and health care applications such as air quality monitoring, toxic gas detection and human breath analyses. With a continuous scaling of CMOS technologies, it is feasible to consider CMOS to significantly reduce the cost and size of rotational spectroscopy systems. An ultra-wideband and low-phase-noise mm-Wave and sub-THz signal generation is essential in a rotational spectroscopy system to improve its detection sensitivity. In this dissertation, sub-THz signal generation systems with novel circuit techniques are proposed in CMOS process to generate high purity local oscillator (LO) signals with ultra-wideband from 60 GHz to 280 GHz. Firstly, magnetic-tuning technique for varactor-less mm-Wave/sub-THz oscillators is analyzed and discussed. Based on the results, a dual-band voltage-controlled oscillator (VCO) prototype is proposed to achieve a frequency tuning range from 95.7 GHz to 110.5 GHz with FoM
T of -181.7 dBc/Hz while consuming 6.2 mW. In addition, for quadrature signals generation, a transformer coupling quadrature VCO (TC-QVCO) prototype is proposed with a frequency tuning range from 89.4 GHz to 100.9 GHz and phase error less than 2.6°. Moreover, a fundamental sub-THz oscillator prototype is designed and demonstrated near the f
max with a peak output power of -12.1 dBm and frequency tuning range from 157.8 GHz to 166.3 GHz, and a 340-GHz push-push oscillator above the f
max is also presented. Secondly, an ultra-wideband sub-THz signal generation system is proposed for rotational spectroscopy employing a magnetic-tuning varactor-less quad-band oscillator (QB-VCO), a locking-range-enhanced dual-mode injection-locked frequency divider (DM-ILFD), a power-efficient injection-locked oscillator (ILO) as a driver, and self-mixing-based frequency multipliers (FMs) for frequency extension. The QB-VCO demonstrated a continuous frequency tuning range of 32% at around 70 GHz. The proposed novel dual-mode DM-ILFD achieves a locking-range of 31.8% in the divide-by-2 mode and 41.2% in the divide-by-4 mode, respectively. The signal generation system achieves a record frequency tuning range from 58.8 GHz to 275.6 GHz with FoM
T of -190.4 dBc/Hz while consuming only 54 mW. Thirdly, a harmonic extraction technique is proposed to enhance the third-harmonic amplitude and further improve the phase noise performance of the sub-THz LO generation. Based on this technique, a scalable cascaded injection-locked frequency multiplier chain architecture is proposed, which can generate sub-THz signal from a low RF tone. A prototype of a cascaded two-stage ILFM-based sub-THz LO generation is demonstrated with ultra-low power consumption of 2.5 mW. The prototype achieves a frequency tuning range of 23.7% from 153.9 GHz to 195.3 GHz with a phase noise of -106.8 dBc/Hz at 10-MHz offset, corresponding to FoM of -186.5 dBc/Hz and FoM
T of -194.1 dBc/Hz. Finally, by employing a radio frequency (RF) sub-sampling PLL (SS-PLL) cascaded with an injection-locked-based mm-Wave LO generation chain, and a sub-THz mixer and push-push extraction for frequency extension, a fully integrated wideband and low phase noise sub-THz frequency synthesizer is proposed for the rotational spectroscopy system. Third-harmonic and fourth-harmonic enhancement methods are proposed for the ILFMs with different multiplication ratios. In addition, a novel frequency tracking loop (FTL) with automatic frequency and amplitude calibration is proposed for the ILFMs. Moreover, a distributed biased technique is also proposed to improve the linearity of the wideband sub-THz oscillator. Designed with 65-nm CMOS process, the sub-THz frequency synthesizer measures a close-loop frequency tuning range from 61.2-to-100.8 GHz, 122.4-to-136.8 GHz and 198.5-to-273.6 GHz, measures a close-loop phase noise from -79.3 dBc/Hz to -95.4 dBc/Hz at 1-MHz offset across the whole tuning range, achieves an integrated jitter of 124 fs, demonstrates an output power of -11 dBm and DC-to-RF efficiency of 0.16% at the frequency above 200 GHz.
| Date of Award | 2019 |
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| Original language | English |
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| Awarding Institution | - The Hong Kong University of Science and Technology
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