Sigma-Delta ADC Bandwidth Calibration Using Quantization Noise
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Solution Overview
Problem
Sigma delta analog to digital conversion circuits face challenges in controlling the bandwidth of filtering circuits due to manufacturing spread when using different analog circuit elements like capacitances and resistances, making it difficult to regulate the time constant and maintain effective operation.
Innovation Solution
A sigma delta analog to digital converter with a detector to measure signal strength in frequency bands where noise-shaped quantization noise rises, using this information to control the time constant of the filtering circuit, thereby calibrating and regulating the bandwidth, especially in time-continuous filtering circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If different analog circuit elements (capacitances and resistances) are used in the filtering circuit, then the filtering circuit can be realized as a time-continuous circuit, but manufacturing spread affects the ratio between impedances making it difficult to control the bandwidth
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the time constant of the filtering circuit through a control circuit that modifies the resistance value based on detected signal characteristics. This allows the system to compensate for manufacturing variations and maintain precise bandwidth control despite using different analog circuit elements with inherent spread in their impedance values.
Solution Approach 2:
The patent implements feedback by using a detector to monitor the output signal of the sigma-delta modulator and feeding this information back to a control circuit that adjusts the filtering circuit's time constant. This closed-loop feedback mechanism enables automatic compensation for manufacturing spread and maintains accurate bandwidth control in time-continuous filtering circuits.
2Manufacturing precision
If all-capacitance filtering circuit is used, then manufacturing spread is minimized, but the circuit can only be realized by switched capacitance techniques (discrete time techniques)
Solution Approach 1:
The patent uses composite materials by combining capacitance and resistance elements in the filtering circuit. This composite approach allows the realization of time-continuous filtering while managing manufacturing spread through dynamic control of the resistance component, achieving both continuous time operation and acceptable manufacturing precision.
Solution Approach 2:
The patent applies dynamics by making the filtering circuit's time constant adjustable rather than fixed. The control circuit dynamically modifies the resistance value based on real-time detection of signal characteristics, enabling the circuit to adapt to manufacturing variations and maintain proper bandwidth control in time-continuous operation.
3Reliability
If the time constant of the filtering circuit is not regulated, then the circuit operation becomes unstable due to manufacturing spread, but regulating it requires additional control mechanisms
Solution Approach 1:
The patent implements feedback by using a detector to monitor the output signal of the sigma-delta modulator and feeding this information back to a control circuit that adjusts the filtering circuit's time constant. This closed-loop feedback mechanism enables automatic compensation for manufacturing variations and maintains accurate bandwidth control in time-continuous filtering circuits.
Solution Approach 2:
The patent applies self-service by enabling the filtering circuit to automatically adjust its own time constant based on signals detected from the system's own operation. The control circuit uses the modulator's output signal to regulate the filtering parameters, allowing the system to self-compensate for manufacturing spread without requiring external calibration or complex additional control mechanisms.
Data Source
AI summary
A signal processing circuit comprising a sigma delta analog to digital converter with a feedback loop that comprises an analog filtering circuit (14) that has a controllable time constant. In a calibration mode, a detector (18) detects a signal strength in a band (34) of frequencies at an output of the sigma delta analog to digital converter. A bandwidth control circuit (19) has an output coupled to a control input of the analog filtering circuit (14), and is arranged to control said time constant dependent on a signal strength in a band (34) of frequencies at the output of the sigma delta analog to digital converter. The band (34) of frequencies is selected so that noise shaped quantization noise density (32) of the sigma delta analog to digital converter rises with frequency.