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978-3-8439-4237-9, Reihe Elektrotechnik
Wideband Low Phase Noise 60 GHz Push-Push Oscillators in Advanced CMOS Technologies for FMCW Radar Applications
144 Seiten, Dissertation Universität Erlangen-Nürnberg (2019), Softcover, A5
The unlicensed 60 GHz frequency band provides an outlook for new applications, such as near-field FMCW radars for gesture recognition. This drives the research on mm-wave circuits in advanced CMOS technologies. Highly integrated systems fabricated in these technologies for high-volume products have the potential to lower costs, which is crucial for the success on the market.
The voltage-controlled oscillator (VCO) is a critical building block for the FMCW radar system. A wideband continuous frequency-tuning-range (FTR) and low phase noise are challenging specifications. The SiGe HBT technologies are preferred over CMOS technologies because of transistor speed and noise. Especially the phase noise is still a major disadvantage of VCOs fabricated in CMOS technologies because of low Q factor and high flicker noise.
The focus of this thesis is on the examination of three circuit techniques for 60 GHz push-push CMOS VCOs that improve the phase noise performance while simultaneously maintaining a continuous wideband FTR: transformer-based core-coupling, superharmonic tail-node-coupling and adaptive gate-biasing. The VCOs with coupling techniques are multi-core designs. The measurements successfully prove the expected relative phase noise improvement in dependency on the number of coupled VCO cores while the FTR remains wideband. The comparison of an adaptive gate-biased to a self-biased VCO results in mostly equivalent phase noise performance and FTR. This proves successfully that biasing of the VCO core is feasible without performance penalty and tail current source.
The VCOs are fabricated in three different foundry-based advanced CMOS technologies that were enabled for mm-wave circuit design during the doctorate studies: 22 nm FD SOI, 28 nm bulk and 45 nm PD SOI. The results presented in this dissertation are one of the first in the respective technologies. However, a comparison among the technologies is not possible and not intended.