Sigma delta modulator having enlarged dynamic range due to stabilized signal swing
First Claim
1. An analog-to-digital converter comprisinga sigma-delta-modulator comprising a plurality of cascaded integrators, a comparator for signal quantization, monitoring means adapted to monitor a signal swing of an output signal of at least one of the plurality of integrators and to determine if the monitored signal swing exceeds a predefined threshold value, the predefined threshold value being associated with a maximum stable input amplitude of the sigma-delta-modulator, and controlling means adapted to reduce the output signal of at least one of the plurality of integrators by a predefined factor or value so as to bring the monitored signal swing below the predefined threshold value.
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Abstract
A method for designing a single loop Sigma Delta Modulator, and a single loop Sigma Delta Modulator. A microphone comprising the above Sigma Delta Modulator (SDM) and a cellular phone or hearing aid incorporating the microphone. A design algorithm for an SDM is described said method resulting in a SDM with a maximum SNR for a given NTF order and the method assures stability while still keeping the distortion in the output signal at a minimum for signals exceeding MSA. The method further takes the presence of non idealities in i.e. components into consideration and makes the SDM less sensitive to these non idealities. Furthermore the method tailors the coefficients and the design of the NTF to fit a low power low voltage integrated circuit implementation.
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Citations
7 Claims
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1. An analog-to-digital converter comprising
a sigma-delta-modulator comprising a plurality of cascaded integrators, a comparator for signal quantization, monitoring means adapted to monitor a signal swing of an output signal of at least one of the plurality of integrators and to determine if the monitored signal swing exceeds a predefined threshold value, the predefined threshold value being associated with a maximum stable input amplitude of the sigma-delta-modulator, and controlling means adapted to reduce the output signal of at least one of the plurality of integrators by a predefined factor or value so as to bring the monitored signal swing below the predefined threshold value.
Specification