On the use of chaos to reduce idle-channel tones in delta-sigma modulators

Delta-sigma modulators are popular circuits for constructing high precision analog-to-digital and digital-to-analog converters. These systems contain a single nonlinear element (a quantizer) embedded in an otherwise linear system, and can exhibit such nonlinear behavior as limit cycles, subharmonics, phase-locking and chaos. Due to the discrete spectra that result when limit cycles are present, human listeners perceive objectionable tones in the quantization noise. This problem can be overcome by using dither or, as this paper suggests, by making the modulator chaotic. The effectiveness of the technique is illustrated and its impact on modulator complexity, stability, and performance is discussed.