Sigma-Delta ADC Feedback Control for Blocker Signal Stability
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Solution Overview
Problem
Sigma-delta modulator ADCs face instability due to out-of-band signals, known as images or blockers, which interfere with the conversion process and are not effectively suppressed by existing technologies.
Innovation Solution
An ADC configuration that includes a sigma-delta modulator, a decimation filter, and a detection circuit, where the detection circuit monitors node voltages and generates control signals to adaptively adjust the loop filter, quantizer, feedback path, and feedforward path to suppress unwanted signals, thereby improving stability and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional sigma-delta modulator ADC is used, then the ADC structure is simple, but out-of-band signals interfere with the conversion process causing instability
Solution Approach 1:
The detection circuit performs preliminary detection of out-of-band signals before they can interfere with the conversion process. By detecting the presence and strength of image signals in advance, the system can proactively adjust the loop filter coefficients to suppress these interfering signals, preventing instability before it occurs.
Solution Approach 2:
The patent implements a feedback mechanism where the detection circuit continuously monitors the output of the sigma-delta modulator for out-of-band signals. When image signals are detected, the system feeds back control signals to adjust the loop filter coefficients, creating a closed-loop control system that maintains stability by continuously counteracting interfering signals.
2Reliability
If out-of-band signals are not suppressed, then the ADC operation is simple, but the conversion process becomes unstable due to image interference
Solution Approach 1:
The patent implements a feedback mechanism where the detection circuit continuously monitors the output of the sigma-delta modulator for out-of-band signals. When image signals are detected, the system feeds back control signals to adjust the loop filter coefficients, creating a closed-loop control system that maintains stability by continuously counteracting interfering signals.
Solution Approach 2:
The detection circuit and control mechanism operate autonomously to detect and suppress out-of-band signals without requiring external intervention. The system self-adjusts the loop filter coefficients based on real-time detection of image signals, enabling the ADC to maintain stability through self-service operation.
3Reliability
If adaptive adjustment of loop filter coefficients is implemented, then stability is improved, but power consumption increases
Solution Approach 1:
The detection circuit operates periodically to detect out-of-band signals rather than continuously. By sampling the output at specific intervals and adjusting loop filter coefficients only when image signals are detected, the system reduces unnecessary power consumption while maintaining stability when needed.
Solution Approach 2:
The system dynamically changes the parameters of the loop filter coefficients based on detected signal conditions. By adjusting coefficients only when out-of-band signals are present and returning to default values when conditions are normal, the system optimizes the balance between stability and power consumption by changing parameters only when necessary.
Data Source
AI summary
An analog-to-digital converter (ADC) is provided. The ADC receives an analog input signal and generates a digital code. The ADC includes a sigma-delta modulator (SDM), a decimation filter and a detection circuit. The SDM includes a loop filter, a quantizer and a digital-to-analog converter (DAC). The loop filter receives the analog input signal. The quantizer is coupled to the loop filter and quantizes an output of the loop filter to generate a digital output signal. The DAC is coupled to the quantizer and the loop filter. The decimation filter is coupled to the SDM and converts the digital output signal into the digital code. The detection circuit is coupled to the SDM and detects a node voltage of the SDM and generate a control signal. The control signal is utilized to control the loop filter, the quantizer, a feedback path of the SDM and/or a feedforward path of the SDM.