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-nois...[
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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.
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