Dual-Quantizer ADC Recombination for Lower Quantization Noise
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Solution Overview
Problem
Analog-to-digital converters with dual in-loop quantization face challenges in reducing quantization noise and manipulating the signal transfer function, particularly in achieving a unity transfer function for enhanced bandwidth and response to sudden changes.
Innovation Solution
The proposed solution involves an analog-to-digital converter with a feedback loop using two quantizers, where the first quantizer has a lower resolution and the second quantizer is more upstream, allowing for adaptive recombination filters to eliminate or reduce quantization noise and modify the signal transfer function, thereby improving dynamic response and reducing quantization noise contributions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If dual in-loop quantization is used to reduce feedback DAC complexity, then device complexity is reduced, but quantization noise increases
Solution Approach 1:
An intermediate digital filter is introduced between the first quantizer and the second quantizer to process the quantized signal before it enters the feedback path. This intermediary filter enables proper noise shaping and signal reconstruction, allowing the system to achieve low quantization noise while maintaining the simplified dual-quantizer architecture with reduced feedback DAC complexity.
Solution Approach 2:
The patent implements a feedback mechanism where the output of the second quantizer is fed back through the digital filter to the input of the first quantizer. This feedback loop enables noise shaping that pushes quantization noise to higher frequencies while maintaining accuracy in the signal band, thus reducing the impact of quantization noise despite using lower-resolution quantizers.
2Speed
If the signal transfer function is made equal to one for enhanced bandwidth, then response speed is improved, but device complexity increases
Solution Approach 1:
The patent achieves a unity signal transfer function by carefully selecting and adjusting the parameters of the digital filter, specifically its transfer function characteristics. By designing the digital filter with appropriate coefficients and structure, the system obtains H(z) = 1 in the signal band, achieving enhanced bandwidth and fast response without requiring complex additional circuitry beyond the existing dual-quantizer and digital filter architecture.
Data Source
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AI summary
The present invention relates to an analog-to-digital converter comprising - a first quantizer (13) arranged for yielding a first digital signal (D1), - an error signal generation block (11) arranged for generating an error signal (14) representative of a difference between an analog input signal (Vi;θi) and said first digital signal (D1), - an analog loop filter (121) arranged for receiving said error signal - a second quantizer (122) arranged for receiving an output signal of said analog loop filter and for outputting a second digital signal (D2), - a digital loop filter (123) arranged for receiving said second digital signal and for providing an input signal to said first quantizer, - a recombiner block (2) comprising a first recombination filter (21) arranged to receive said first digital signal, a second recombination filter (22) arranged to receive said second digital signal and an adder circuit for adding outputs of said first and said second recombination filter, said first and said second recombination filter being selected to obtain an analog-to-digital converted output signal (Dout) being less dependent on quantization noise caused by said first quantizer than said first digital signal (D1).