Search ETDs:
Analytical and Experimental Study of Wide Tuning Range Low Phase Noise mm-Wave LC-VCOs
Elabd, Salma

2016, Doctor of Philosophy, Ohio State University, Electrical and Computer Engineering.
The growing interest in commercial high bandwidth communication has set off a wave of research to explore techniques that enable wide tuning range low phase noise voltage-controlled oscillators (VCOs) for mm-wave applications. Conventionally, III-V and BiCMOS technologies have been the most reasonable candidates for implementing such mm-wave circuits. The key advantages provided by these processes are their fast switching speed and low parasitic capacitance due to high substrate resistivity that together enable high frequency VCOs with wide tuning range and low phase noise. However, concerns such as high power consumption, low yield and limited integration levels have led the research and commercial communities to recognize CMOS VCOs to be the most promising candidates for mainstream high-volume mm-wave applications. On the CMOS front, the unabated scaling of device finger length, effective gate oxide thickness and parasitics reduction has tremendously aided analog and digital circuits. Nevertheless, designers are confronted with several key challenges that limit performance and yield in the mm-wave domain.

With this growing interest for VCO frequency tuning range and phase noise reduction, there is a concurrent interest to also have a firm grasp of the fundamental limitations imposed by CMOS technology on the realizing mm-wave VCOs. It is noted that low frequency CMOS VCOs (< 10 GHz) have been well studied and several strategies are available to optimize their performance. However, several challenges remain for mm-wave bands, specifically close to the fT. This motivates the need for analyzing the tuning range and phase noise for mm-wave CMOS VCOs.

This dissertation provides a detailed analysis of performance bounds to simultaneously achieve low phase noise and wide tuning range for CMOS LC-VCOs. The fundamental VCO elements (1- tank inductor, 2- fixed and variable capacitor elements and 3- cross-coupled pair transistors) are analytically modeled across the frequency range of 10-50 GHz. These developed models are exploited to analyze the tuning range by dissecting the interdependence of the tank elements and cross-coupled pair devices. Subsequently, this quantitative analysis is used to optimize the VCO performance in a closed-loop form and establish minimum phase noise bounds across the frequency range of interest. The analysis is conducted using a 130 nm CMOS process, and confirmed by measurement results on three VCOs at 26 GHz, 34 GHz and 40 GHz. Next, the impact of CMOS technology scaling on achievable performance bounds is studied. A performance trend comparison between VCOs implemented using thin gate and thick gate cross-coupled devices is conducted across the frequency range of 10-50 GHz and for CMOS technology scaling from 130 nm down to 45 nm. In this regard, performance bounds including phase noise, tuning range, and figures-of-merit (FoM and FoMT) are presented.

This dissertation also addresses the performance trends of MOS and HBT VCOs across the 10-70 GHz mm-wave band. Specifically, the trade-offs between the phase noise and tuning range are provided. In addition, a phase noise comparison of mm-wave MOS and HBT LC-VCOs in the `close-in' and `far-off' regions is given. In this regards, the impact of different circuit parameters on phase noise performance in both VCOs is studied, and the trade-offs between improving flicker noise and thermal noise are considered.

A key aspect of this dissertation is a wide frequency tuning range and low phase noise mm-wave BiCMOS LC-VCO. The proposed architecture employs dual switchable negative capacitance and current redistribution to simultaneously achieve low phase noise and wide frequency tuning range while saving power consumption. The new VCO architecture achieves a record FoMT of -194.5 dBc/Hz among the state-of-the-art mm-wave VCOs. Fabrication is carried out using 130 nm SiGe process is utilized to design and fabricate this VCO with a center oscillation frequency of 34 GHz and frequency tuning range of 35%.
Waleed Khalil (Advisor)
John Volakis (Committee Member)
Marvin White (Committee Member)
Han-Wei Shen (Committee Member)
250 p.

Recommended Citations

Hide/Show APA Citation

Elabd, S. (2016). Analytical and Experimental Study of Wide Tuning Range Low Phase Noise mm-Wave LC-VCOs. (Electronic Thesis or Dissertation). Retrieved from https://etd.ohiolink.edu/

Hide/Show MLA Citation

Elabd, Salma. "Analytical and Experimental Study of Wide Tuning Range Low Phase Noise mm-Wave LC-VCOs." Electronic Thesis or Dissertation. Ohio State University, 2016. OhioLINK Electronic Theses and Dissertations Center. 23 Nov 2017.

Hide/Show Chicago Citation

Elabd, Salma "Analytical and Experimental Study of Wide Tuning Range Low Phase Noise mm-Wave LC-VCOs." Electronic Thesis or Dissertation. Ohio State University, 2016. https://etd.ohiolink.edu/

Files

Full text release has been delayed at the author's request until August 11, 2021