J. O. Coleman

Modeling Finite-Memory Nonlinearity in Unit DAC Elements, Binary Storage Channels, and BPSK Data Channels
J. O. Coleman
Spectral shaping of quantization noise can allow a few (or one) oversampled D/A converters restricted to two output levels, unit DAC elements, to replace high-resolution converters. In high-resolution or high-speed settings however, even the performance of systems with only two output levels can be limited by conversion-circuit nonlinearities that introduce quantization-noise intermodulation products into the signal band through nonlinear intersymbol interference (ISI). Nonlinear ISI also affects the communication and magnetic storage of data. Here a simple but very general model structure for such binary-in, analog-out nonlinearities is proposed. Curiously, its structure is that of a convolutional coder whose output bits are separately LTI filtered before being finally summed to form the analog output. The largest-energy filter responses have natural interpretations if this convolutional code is chosen carefully. One such code is presented here.
PDF (205 Kbytes),
Presented to the 17th European Conf. on Circuit Theory and Design (an IEEE conference), Cork, Ireland, Aug 29 - Sep 1, 2005.
March 2005. Updated May 2005 and September 2005.