BER-Optimal Analog-to-Digital Converters for Communication Links

Abstract

In this paper, we propose low precision <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BER</i> -optimal analog-to-digital converters (ADC) where quantization levels and thresholds are set nonuniformly to minimize the bit-error rate ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BER</i> ) in a high data rate communication link. This is in contrast to how ADCs are used today, in which they act as transparent waveform preservers. Simulations for various communication channels show that for 2-PAM modulation, the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BER</i> -optimal ADC achieves shaping gains that range from 2.5 dB for channels with low intersymbol interference (ISI) to more than 30 dB for channels with high levels of ISI. Moreover, a 3-bit <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BER</i> -optimal ADC achieves the same or even lower <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BER</i> than a 4-bit uniform ADC. With a DFE and a high-ISI channel, a 3-bit <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BER</i> -optimal ADC achieves lower <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BER</i> than a 5-bit uniform ADC.