Programmable Loop Filter for Sigma-Delta ADC Bandwidth Adaptation
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Solution Overview
Problem
General purpose sigma delta ADCs face limitations in providing a dynamic range commensurate with varying input signal bandwidths, resulting in suboptimal performance across different applications.
Innovation Solution
A programmable loop filter with a configurable filter structure and configuration controller is introduced, allowing for selective interconnection of filter elements to determine the transfer characteristic and set operating conditions of the sigma delta ADC, enhancing signal-to-noise ratio and dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a general purpose sigma delta ADC is designed to accommodate a wider input signal bandwidth (e.g., 100 kHz), then the bandwidth capability is improved, but the dynamic range deteriorates because the equivalent noise level increases
Solution Approach 1:
The loop filter is designed with programmable transfer characteristics that can be dynamically adjusted based on the input signal bandwidth requirements. The filter coefficients are programmable, allowing the system to switch between different filter configurations to optimize performance for different bandwidth scenarios, thereby maintaining high dynamic range even when accommodating wider bandwidths.
Solution Approach 2:
The invention changes the parameters of the loop filter by making its transfer characteristic programmable. Different sets of filter coefficients can be loaded to match different input signal bandwidth requirements. This allows the system to adapt the noise shaping characteristics to maintain optimal signal-to-noise ratio and dynamic range across varying bandwidth conditions.
2Device complexity
If the loop filter transfer characteristic is fixed, then the device complexity is reduced, but the adaptability to different bandwidth requirements deteriorates
Solution Approach 1:
The loop filter is designed to perform multiple functions by incorporating programmable coefficients that can be configured for different bandwidth scenarios. A single filter structure serves multiple purposes by loading different coefficient sets, eliminating the need for multiple dedicated filters for different bandwidth requirements and thereby reducing overall device complexity while maintaining high adaptability.
Solution Approach 2:
The filter transitions from a static, fixed characteristic design to a dynamic, programmable design. The ability to reconfigure the transfer characteristic in response to different input signal conditions provides the necessary adaptability without requiring multiple separate filter circuits, thus maintaining simplicity while enhancing versatility.
Data Source
AI summary
The present invention is directed to a programmable loop filter, a method of programming the same and a sigma delta analog-to-digital converter (ADC) incorporating the programmable loop filter or the method. In one embodiment, the programmable loop filter includes: (1) a configurable filter structure containing selectably interconnectable alternative filter elements and (2) a configuration controller coupled to the configurable filter structure and operable to interconnect at least a selected one of the filter elements to determine a transfer characteristic of the configurable filter structure and set an operating condition of the sigma delta ADC.