Optimization of ring oscillators

• Author(s): Leal, João Filipe Tapadinhas Puga
• Date: 2013
• Persistent ID: http://hdl.handle.net/10362/11361
• Origin: Repositório Institucional da UNL
• Subject(s): VCOs; Ring oscillator; Phase-noise; Optimization
• Document Type: Master thesis
• Language: English
• Advisor(s): Fino, Maria Helena
• Contributor(s): RUN

Description

Dissertação para obtenção do Grau de Mestre em Engenharia Electrotécnica e de Computadores

Voltage Controlled Oscillators (VCOs) are from all the building blocks of a PLL, those whose implementation is more critical, since the quality of the signal depends on its performance. The VCOs can be implemented based on LC oscillators or ring oscillators. The ring oscillators, despite of being worst when it comes to manners of phase noise, they are rather used due to lower power consumption, wider tuning range and occupying less area. Despite the fact that VCOs are widely used in last years, their designed is still a problem hard to deal with, since the ring oscillators circuits must satisfy some specifications such as area, power, speed and noise. The work proposed in this thesis aims at the development of an environment for automatic scaling of voltage-controlled oscillators with ring topology. In this work it was considered a design methodology based optimization using an analytical model of the oscillator. The oscillator model is based on the EKV model for the characterization of the transistors so as to ensure its applicability to submicron dimensions technologies. The work took place according to the following phases: - Study of ring oscillators and models proposed in the literature - Evaluation of the limitations of existing models and proposed use of EKV model. - Automatic determination of the parameters of the EKV model for UMC130 technology - Development of an analytic model for characterizing the VCO with predefined delay cell. - Use of optimization techniques for automatic sizing of the VCOs