Dissertation Defense

Phase Control in Electrical Coupled Oscillators: Theory and Applications

Vahnood PourahmadPh.D CandidateCornell University

Oscillators are one of the key blocks in many RF integrated circuits and systems. Among different configurations, coupled oscillators are widely known for their favorable properties in terms of generated signal quality. Controlling the relative phase shift of coupled oscillators becomes important in various applications. Examples include quadrature phase generation in image reject receivers, high data rate sampling circuits, clock distribution networks, novel associative memory paradigms and phased array systems for beam scanning.
In this work, we study the nonlinear dynamics of coupled oscillators, explain how it predicts interesting frequency tuning effects in a ring of varactor-free coupled oscillators and present experimental verifications with a 65nm CMOS prototype chip. We also present a novel way of generating continuous arbitrary phase shifts between coupled oscillators by controlling relative strengths of different coupling channels between them. Measurement results for a prototype chip fabricated in a standard 130nm CMOS technology verifies the theory and paves the way for implementing the proposed structure for coupled oscillator based phased arrays at mm-wave frequencies. We also study associative memory effects in coupled oscillator networks and propose a new physical system for pattern classification. The compact layout and simplicity of our proposed structure makes it readily implementable in any standard CMOS technology.
Vahnood Pourahmad received his BSc degree in civil engineering from Sharif University of Technology in 2008. He then obtained two MSc degrees from Cornell University in the fields of theoretical and applied mechanics and electrical and computer engineering in 2012 and 2016 respectively. He is now pursuing his PhD degree in electrical and computer engineering from Cornell University. Vahnood is recipient of Cornell's McMullen fellowship in 2008 and Jacobs fellowships in 2014.

Sponsored by


Faculty Host

Ehsan Afshari