Non-Boolean Associative Processing: Circuits, System Architecture, and Algorithms

We present the design and the performance of a hierarchical associative memory (AM) based on phase locking of coupled oscillators used for pattern recognition. The use of coupled oscillators, rather than Boolean logic, provides for implementations using emerging nanotechnology, such as magnetic spin-torque oscillators and resonant body transistor oscillators, which have the potential of lower energy and higher density than CMOS solutions. We develop a model for the general behavior of weakly coupled nonlinear oscillators that perform pattern matching using a simulation of coupled CMOS ring oscillators. We derive a simple analytic model for their phase locking behavior and use this reduced model in a hierarchical AM for image recognition tasks, such as identifying handwritten numbers.