Chaotic complex‐valued bipartite auto‐associative memory with a periodic activation function

A Hopfield associative memory (HAM) can store binary data. A HAM has been extended to a complex‐valued HAM (CHAM) which can store multi‐level data. A CHAM has often been applied to the storage of grayscale images. A CHAM has a problem of rotational invariance, which makes many psuedomemories and reduces the noise tolerance. A chaotic CHAM can explore the stored patterns, though it recalls many pseudomemories. A complex‐valued bipartite auto‐associative memory (CBAAM) was proposed to improve the noise tolerance by solving rotational invariance. Since a CBAAM stores the reversed patterns, a chaotic CBAAM (CCBAAM) recalls both the training and reversed patterns. In order to solve this problem, a periodic activation function is introduced. A periodic activation function identifies the training and reversed patterns, so that a CCBAAM does not recall the reversed patterns. We evaluate our proposed CCBAAM by computer simulations. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.