Feedforward Sigma-Delta ADC with Direct Path Peaking Compensation
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Solution Overview
Problem
Conventional sigma-delta ADC architectures face challenges with high energy consumption due to the need for extensive linear bandwidth and dynamic range to prevent intermodulation distortion from interferers, and they require significant analog pre-filtering, which introduces noise and complexity.
Innovation Solution
The proposed ADC architecture incorporates a direct feedforward path with a scaling functionality to compensate for peaking and provide alias filtering, reducing the need for analog pre-filtering and allowing the ADC to be integrated closer to the receiver input, while maintaining interferer immunity and low-power constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional sigma-delta ADC architecture is used with extensive linear bandwidth and dynamic range, then intermodulation distortion from interferers is prevented, but energy consumption increases
Solution Approach 1:
The invention segments the filtering function into two parts: analog pre-filtering (first filter section) and digital filtering (second filter section). This segmentation allows the analog pre-filter to handle only essential anti-aliasing while the digital filter handles the majority of signal conditioning, reducing the bandwidth requirements and energy consumption of the ADC itself while maintaining interferer immunity.
Solution Approach 2:
The invention replaces extensive analog pre-filtering (mechanical/analog system) with digital filtering processing. By using a digital filter section that processes the quantized signal, the system achieves superior filtering performance with lower power consumption and reduced hardware complexity compared to traditional analog filter approaches.
2Measurement precision
If significant analog pre-filtering is used, then alias filtering is improved, but noise and complexity increase
Solution Approach 1:
The invention replaces complex analog pre-filtering circuits with a digital filter section that performs filtering in the digital domain. This substitution eliminates the noise and complexity inherent in analog filter components while achieving superior alias rejection through digital signal processing techniques.
Solution Approach 2:
The invention introduces a quantizer as an intermediary element between the analog pre-filter and the digital filter. This quantizer converts the analog signal to digital form, enabling the subsequent digital filter to perform precise alias filtering without the limitations and noise associated with purely analog filtering stages.
3Productivity
If ADC is integrated closer to receiver input, then signal processing efficiency is improved, but analog pre-filtering requirements increase
Solution Approach 1:
The invention segments the filtering functionality between a minimal analog pre-filter section and a comprehensive digital filter section. This allows the ADC to be integrated close to the receiver input with minimal analog pre-filtering requirements, while the digital filter section handles the bulk of signal conditioning, maintaining processing efficiency without excessive analog complexity.
Data Source
AI summary
The present invention relates to a receiver apparatus, analog-to-digital converter apparatus, and method of converting an analog input signal into a digital output signal, wherein an additional direct feedforward path is introduced to compensate for peaking of feedforward structures while preserving frequency selectivity of the feedforward topology. In particular, the direct feedforward path (72) is provided with a scaling by a direct feedforward coefficient (ao) greater than zero and less than one. As a result, overshoot or peaking of classical feedforward topologies can be suppressed while providing interferer immunity, anti-aliazing effects and loop stability.