Stabilization of single bit high order interpolative sigma delta modulators for analog-to-digital conversion in wireless mobile handset based electromyogram acquisition system

摘要

Wireless mobile handsets are widely used for the electromyogram acquisitions because of their portability property. However, as the electromyograms are with low amplitudes and they are very sensitive to the noises, a good analog-to-digital conversion system plays a very important role for the processing of the electromyograms. Among all the analog-to-digital converters, the sigma delta modulator is the most common analog-to-digital convertor employed in the mobile handsets. This is because the oversampling mechanism for bandlimited signals can be implemented using the existing hardware. However, the sigma delta modulator may suffer from the stability issue. This paper considers the stabilization of a single bit high order interpolative sigma delta modulator via flipping some values of the quantizer output. The values of the quantizer output are determined in such that certain frequency contents of the input signal are cancelled by those of the quantizer output. A stability condition for the proposed control strategy is derived. Since only some frequency detectors and a simple inverter are required for the implementation of the proposed control strategy, the implementation cost is low.