Code division parallel delta-sigma A/D converter with probabilistic iterative decoding

We investigate modulation-based parallel delta-sigma (ΔΣ) converters for wideband A/D conversion applications. A code division parallel ΔΣ conversion method is proposed, where each path consisting of a ΔΣ modulator operates on an input signal modulated with different binary code. In contrast to standard Hadamard based modulation schemes, the design provides flexibility in choosing the number of parallel paths and the type of binary modulation sequences. We exploit the information-theoretical approach to design an iterative probabilistic decoding procedure for optimal decoding of the ΔΣ modulator outputs. To demonstrate the decoding method, a maximum a posteriori probability decoder for the first order ΔΣ modulator is developed. Simulation results verify the iterative decoding procedure, demonstrate the use of arbitrary number of paths, and show that the A/D converter based on pseudo-random sequences achieves improved spurious-free dynamic range.