Delta-Sigma Modulator Feedback for Inter-Symbol Interference Reduction
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Solution Overview
Problem
Delta-sigma modulators in mobile communication systems face challenges with inter-symbol interference (ISI) that existing pre-distortion techniques fail to address effectively, particularly when the final stage input signal originates from a delta-sigma modulator, leading to spectral distortions and interference issues.
Innovation Solution
A delta-sigma modulator with a feedback signal modifier that adjusts feedback signals based on actual and preceding output values, using a look-up table or coefficients to compensate for ISI effects, allowing for efficient reduction of inter-symbol interference in the output signal, and incorporating a control unit for updating the look-up table to adapt to time-dependent variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If pre-distortion of the final stage input signal is used, then spectral distortions are reduced, but it fails to effectively address inter-symbol interference when the signal originates from a delta-sigma modulator
Solution Approach 1:
The patent introduces a feedback mechanism where the output of the final delta-sigma modulator stage is fed back through a feedback signal modifier that adjusts the feedback signal based on preceding output values. This feedback loop dynamically compensates for inter-symbol interference by modifying the feedback path to account for the specific characteristics of delta-sigma modulated signals, thereby resolving the inadequacy of conventional pre-distortion techniques.
Solution Approach 2:
The feedback signal modifier performs preliminary adjustment of the feedback signal before it is applied to the final stage. By pre-modifying the feedback signal based on preceding output values stored in memory, the system proactively compensates for expected inter-symbol interference effects, improving spectral performance before the interference can degrade the output signal.
2Manufacturing precision
If complex pre-distortion techniques are implemented to reduce spectral distortions, then spectral performance improves, but device complexity increases
Solution Approach 1:
Instead of implementing complex pre-distortion processing before the final stage, the patent uses a feedback mechanism that operates on the actual modulator output. This feedback approach is inherently simpler because it directly measures and compensates for the actual interference present in the delta-sigma modulated signal, rather than attempting to predict and correct for all possible distortion scenarios in advance.
Solution Approach 2:
The delta-sigma modulator system performs its own interference compensation through the feedback signal modifier that is integrated into the modulator architecture. The system uses its own output signal and preceding values to generate the correction, eliminating the need for separate complex pre-distortion processing blocks and reducing overall device complexity.
3Device complexity
If conventional feedback is used without modification, then device complexity is low, but inter-symbol interference is not effectively reduced
Solution Approach 1:
The patent enhances conventional feedback by introducing a feedback signal modifier that processes the feedback signal based on preceding output values. This modified feedback mechanism maintains the simplicity of the basic feedback structure while adding targeted processing to specifically address inter-symbol interference in delta-sigma modulated signals, achieving improved spectral performance without excessive complexity.
Solution Approach 2:
Rather than applying complex processing throughout the entire signal path, the patent applies localized modification only to the feedback signal. The feedback signal modifier introduces targeted adjustments specifically where needed to compensate for inter-symbol interference, leaving the rest of the system simple and maintaining low overall complexity while improving spectral performance.
Data Source
AI summary
A delta-sigma modulator (1) for converting a delta-sigma modulator input signal into a sequence of delta-sigma modulator output values comprising an actual delta-sigma modulator output value and at least one preceding delta-sigma modulator output value preceding the actual delta-sigma modulator output value is presented. At least one feedback signal modifier for modifying a at least one first feedback signal in dependence of the actual delta-sigma modulator output value and the at least one preceding delta-sigma modulator output value is provided. By means of the at least one first feedback signal modifier the signal quality of a subsequent final stage (7) can be improved.