Predictive Amplitude Limiting for Overshoot-Free Signal Chains
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Solution Overview
Problem
Existing signal processing systems experience amplitude overshoot during band limiting, interpolation, and DAC conversion, leading to signal distortions and artifacts, particularly in FM broadcasting and audio systems, due to insufficient amplitude control.
Innovation Solution
An amplitude limiting device and method that predicts and reduces overshoot by applying an offset to input samples based on filter modeling, using coefficients from subsequent devices to maintain output amplitude within a threshold, with optional smoothing steps to correct notches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If severe attenuation gain or low-threshold clipping is applied to all input samples to keep output magnitude below maximum level, then amplitude overshoot is prevented, but usable output amplitude range is severely reduced
Solution Approach 1:
The patent applies preliminary action by predicting future amplitude overshoot before it occurs using a model of the subsequent device's behavior. The offset is calculated in advance based on the filter model and applied to current input samples, preventing overshoot proactively rather than reacting to it after it occurs. This allows maintaining larger output amplitude range while still preventing the harmful overshoot effects.
2Reliability
If attenuation or clipping is applied to prevent amplitude overshoot, then signal distortion is reduced, but signal quality deteriorates due to severe reduction of amplitude range
Solution Approach 1:
The patent applies local quality by selectively applying offset only to specific input samples that are predicted to cause amplitude overshoot, rather than uniformly attenuating all samples. The offset magnitude is locally adapted based on the predicted overshoot amount for each sample, maintaining signal quality where possible while preventing distortion where necessary.
Solution Approach 2:
The patent changes the parameter of input samples by applying a dynamic offset that varies based on the predicted overshoot. This offset is calculated using the filter model parameters and the specific characteristics of each input sample, allowing precise control that maintains signal integrity without excessive attenuation.
3Manufacturing precision
If band limiting or interpolation is applied to process the signal, then signal quality is improved, but amplitude overshoot and ringing artifacts are introduced
Solution Approach 1:
The patent introduces an intermediary offset calculation step between the input signal and the subsequent device processing. This intermediary computes the predicted overshoot based on a filter model and applies a compensating offset to the input samples before they enter the band limiting or interpolation stage, thereby preventing the generation of ringing artifacts while maintaining the benefits of signal processing.
Data Source
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AI summary
A method (800) comprising: - receiving (850-1) input samples of a signal to be processed by a subsequent device; - performing (850-2) a first limiting step including for at least one sample, replacing the concerned input sample with a reduced sample by applying an offset to the concerned input sample, wherein the reduced sample has the same sign, but a lower magnitude than the concerned input sample, wherein the offset is computed based on parameters of a filter modelling the behavior of the subsequent device and an overshoot difference between a threshold and a predicted output value generated by this filter.