Multi-Bit Sigma-Delta ADC for Rapid Pulse Waveform Capture
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Solution Overview
Problem
Single-bit sigma-delta modulation struggles to accurately capture the shape of rapid transient signals, such as pulses, due to its inability to keep up with the analog waveform, leading to signal overload and loss of waveform information.
Innovation Solution
A multi-bit sigma-delta modulator is introduced, featuring a summation circuit, integrator, and negative feedback circuit with a non-linear relationship between digital output and analog feedback, allowing for more than two levels of quantization and optimized quantization levels to match the temporal properties of the analog input signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If single-bit sigma-delta modulation is used to digitize rapid transient signals, then the system simplicity and power consumption are maintained, but the ability to accurately capture waveform shape is lost due to overload
Solution Approach 1:
The patent changes the quantization parameter from 1-bit to multi-bit (N-bit), enabling the system to represent multiple amplitude levels within each sampling period. This allows accurate capture of rapid transient waveforms while maintaining the oversampling architecture's simplicity and low power consumption characteristics
2Speed
If single-bit digitization is used, then the sampling rate can be kept at realistic levels, but the digitizer cannot keep up with rapid transient analog waveforms leading to overload
Solution Approach 1:
The patent adds a dimension to the digitization process by using multi-bit quantization values that encode both timing and amplitude information. Each N-bit digital value represents not just a single amplitude level but can indicate transitions between levels, effectively capturing rapid transients without requiring proportionally higher sampling rates
3Loss of information
If multi-bit quantization is implemented, then the waveform shape information is preserved, but the relationship between digital output and analog feedback becomes non-linear
Solution Approach 1:
The patent pre-defines the non-linear mapping between N-bit digital values and analog feedback levels during system design. This preliminary configuration of quantization levels and their corresponding analog equivalents allows the feedback circuit to handle non-linear relationships through fixed lookup tables or pre-calibrated DAC settings, rather than requiring complex real-time computation
Data Source
AI summary
A delta sigma modulator includes a summation circuit, at least one integrator, a multi-bit quantizer and a negative feedback circuit. The summation circuit is configured to produce a difference signal between a unipolar or bipolar analog input signal and an analog feedback signal. The integrator is operatively coupled to the summation circuit to integrate the difference signal. The multi-bit quantizer is operatively coupled to the integrator to digitize the integrated signal to generate an N-bit digital output signal, N being an integer greater than 1. The negative feedback circuit operatively couples the multi-bit quantizer to the summation circuit. The negative feedback circuit includes a digital-to-analog converter arrangement for receiving the N-bit digital output signal and providing the analog feedback signal such that digital values of the N-bit digital output signal and values of the analog feedback encoded by the digital values have a non-linear relationship to one another.