Continuous-time sigma-delta modulator design for wireless biomedical sensing applications

This paper discusses the use of continuous-time sigma-delta modulators for ADCs in wireless biomedical sensing applications. The advantages of the proposed continuous-time sigma-delta modulators include the fact that it eliminates the need for an anti-aliasing filter in front of the ADC because of its intrinsic anti-alias filtering property. Additionally, the use of weak inversion and a low flicker noise structure minimizes power consumption and low frequency flicker noise. Finally, the decimation filter used in ordinary sigma-delta ADCs to attenuate high-frequency noise is eliminated because the biomedical sensor analyzes the periodogram in software, thus significantly reducing the cost and power consumption. A design example illustrating these advantages is presented in this paper.