Feedback Compressor Power Limiting for Burst Audio Waveforms
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Solution Overview
Problem
Power limiting circuits fail to accurately manage burst power waveforms, leading to attenuation of signals even when the average power is within limits, due to immediate application of attenuation based on peak power exceedance, which results in failure to pass unattenuated burst waveforms.
Innovation Solution
A feedback compressor circuit configuration that combines an auxiliary attenuation signal with a compressed attenuation signal from a feedback compressor circuit, using a low-pass filter to delay attenuation application, allowing burst power waveforms to pass by calculating an average power level, thereby preventing premature attenuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If immediate attenuation is applied when peak power exceeds threshold, then power limit is enforced, but burst waveforms are attenuated even when average power is within limits
Solution Approach 1:
The patent changes the parameter used for attenuation decision from instantaneous peak power to averaged power over a time window. The power measurement is averaged using a low-pass filter or moving average algorithm, so that brief burst exceedances are smoothed out. This allows the system to enforce power limits based on sustained average power while permitting temporary burst waveforms that stay within average power limits.
Solution Approach 2:
The system performs preliminary averaging of power measurements before applying attenuation. By calculating the average power over a predetermined time window before making attenuation decisions, the system prepares a smoothed power metric that reflects sustained power levels rather than transient peaks, enabling accurate distinction between problematic sustained overpower and acceptable burst waveforms.
2Reliability
If attenuation is applied based on instantaneous power exceedance, then power threshold is maintained, but signal integrity is compromised for burst waveforms
Solution Approach 1:
The patent changes the parameter for attenuation control from instantaneous power to averaged power. By using a low-pass filter with appropriate time constant or moving average calculation, the system measures power over an extended time window, transforming the decision metric from peak-based to average-based. This preserves signal integrity for burst waveforms while maintaining power threshold compliance for sustained overpower conditions.
Solution Approach 2:
The patent introduces an averaging mechanism (low-pass filter or moving average calculator) as an intermediary between power measurement and attenuation control. This intermediary smooths the power signal to extract the average component, separating transient burst information from sustained power levels, and uses this averaged value as the basis for attenuation decisions, thereby protecting burst waveforms from inappropriate attenuation.
3Device complexity
If simple compression is used for power limiting, then implementation is straightforward, but burst power waveforms fail to pass unattenuated
Solution Approach 1:
The patent modifies the compression algorithm by changing the power measurement parameter from instantaneous to averaged. This simple parameter change in the compression logic enables burst waveforms to pass unattenuated while maintaining compression functionality for sustained overpower, achieving improved performance with minimal increase in implementation complexity.
Solution Approach 2:
The patent applies preliminary averaging to the power measurement before feeding it to the compression logic. This preliminary processing step prepares the power metric in a form that naturally permits burst waveforms, and the rest of the compression implementation remains relatively simple, building on existing feedback compressor architecture with minimal additional complexity.
Data Source
AI summary
Example embodiments provide a process that includes one or more of receiving an audio signal from a feedback path of a feedback compressor circuit, determining whether an auxiliary attenuation value applied to the feedback compressor circuit has changed since a last audio signal was received, responsive to determining the auxiliary value has changed, determining a current operational state value of the LPF needs to be modified based on the changed auxiliary attenuation value, modifying the operational state value of the LPF, and applying the audio signal to the modified LPF.