A second-order continuous-time delta-sigma modulator with double self noise coupling

Abstract

In this paper, a second-order continuous-time delta-sigma modulator using double self noise coupling technique is proposed. Noise coupling increases the effective order of the noise shaping loops. The presented architecture splits the outputs of the quantizer into a most significant bit segment (MSBs) and a least significant bit segment (LSBs). The LSBs can be viewed as the residue after the MSBs quantization and is fed back to the front of the quantizer and the second integrator respectively, as a result, double self noise coupling is achieved. In addition, the quantizer also provides a convenient means to incorporate the excess-loop-delay compensation. As a result, the digital noise cancellation logic complexity is simplified, the digital and analog filter mismatch is relaxed, meanwhile, it strictly suppresses the noise within the effective signal bandwidth by reducing the main MSBs mismatch. Finally, the resolution is increased, the hardware complexity and the output swing of the integrator are reduced, which greatly relaxes the bandwidth and gain requirement of the Op-Amp design. The higher order noise shaping introduced by the residue of multi-bit quantizer further reduces the quantization noise.