A programmable analog radial-basis-function based classifier

A 16 x 16 programmable analog radial-basis-function (RBF) based classifier is demonstrated. The distribution of each feature is modeled by a Gaussian function, which is realized by a proposed floating-gate bump circuit having bell-shaped transfer characteristics. The maximum likelihood, mean, and variance of the distribution are stored in floating-gate transistors and are independently programmable. By cascading these floating-gate bump circuits, the overall transfer characteristics approximate a multivariate Gaussian distribution with a diagonal covariance matrix. An array of these circuits constitutes a compact RBF-based classifier. When followed by a winner-take-all circuit, the analog classifier can implement vector quantization. Automatic gender identification is implemented on a 16 x 16 analog vector quantizer chip as one possible audio application of this work. The performance of the analog classifier is comparable to that of digital counterparts. The proposed approach can be at least two orders of magnitude more power efficient than the digital microprocessors at the same task.