Digital-to-analog converters based on Time-Interleaved Sigma-Delta Modulation with Analog Multiplexing

Transceivers built to modern communication standards tend to be as digital as possible, including the radio frequency stages. This forces the transmitter’s digital-to-analog converters (DACs) to have high bandwidth. DACs based on sigma-delta (SD) modulation represent a good choice in modern digital technologies, as they have a simple analog circuit with limited precision requirements. However, the oversampling and technology’s speed limitations impose serious limitations on digital SDM design. In this sense, Time-Interleaving (TI) allows the designer to balance complexity and speed by replacing the original SDM architecture with M parallel paths clocked at a frequency M times lower. The M outputs of the TI architecture are then multiplexed into a single high-speed stream and converted to analog using a single DAC. This article explores the possibility of using low-speed M DACs by means of analog multiplexing. The experimental results provided show that this is a good solution that achieves better performances than using a dedicated high-speed DAC.