Variable Group Delay Audio Output for Low-Latency Noise Filtering

Solution Overview

Problem

Existing audio output systems in personal devices face challenges in achieving low latency and minimizing out-of-band noise while maintaining a high dynamic range, as conventional filtering methods introduce undesirable delay and power dissipation.

Innovation Solution

A system comprising a digital delta-sigma modulator, a filter with variable group delay, and a current-mode digital-to-analog converter is used to receive and process digital audio signals, reducing out-of-band noise and minimizing latency by converting filtered signals into current-mode analog audio signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If out-of-band filtering is applied to reduce ultrasonic noise, then power dissipation is minimized and dynamic range is improved, but audio latency increases due to filter delay

Engineering Contradiction:

Improvepower dissipationVSAvoidaudio latency

Core Design Contradiction:

Loss of energyVSLoss of time

Solution Approach 1:

The filter group delay is made variable rather than fixed, allowing the system to dynamically adjust the delay characteristic based on operating conditions. This enables optimization of both power efficiency and latency performance by adapting the filter behavior to different signal conditions and application requirements.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention changes the filter parameter (group delay) from a static value to a variable parameter that can be adjusted. By modifying the filter's group delay characteristic, the system achieves better power efficiency through effective out-of-band noise rejection while controlling the latency introduced by filtering.

Inventive Principle:

Principle #35Parameter changes

2Object-generated harmful factors

If conventional filtering is used to eliminate out-of-band noise, then spectral folding into audible band is reduced, but undesirable delay is introduced into audio path

Engineering Contradiction:

Improveout-of-band noiseVSAvoidaudio delay

Core Design Contradiction:

Object-generated harmful factorsVSLoss of time

Solution Approach 1:

The filter group delay is made variable rather than fixed, allowing the system to dynamically adjust the delay characteristic based on operating conditions. This enables optimization of both power efficiency and latency performance by adapting the filter behavior to different signal conditions and application requirements.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention changes the filter parameter (group delay) from a static value to a variable parameter that can be adjusted. By modifying the filter's group delay characteristic, the system achieves better power efficiency through effective out-of-band noise rejection while controlling the latency introduced by filtering.

Inventive Principle:

Principle #35Parameter changes

3Use of energy by moving object

If high dynamic range operation is pursued with aggressive out-of-band filtering, then power consumption is reduced, but audio latency increases

Engineering Contradiction:

Improvepower consumptionVSAvoidaudio latency

Core Design Contradiction:

Use of energy by moving objectVSLoss of time

Solution Approach 1:

The filter group delay is made variable rather than fixed, allowing the system to dynamically adjust the delay characteristic based on operating conditions. This enables optimization of both power efficiency and latency performance by adapting the filter behavior to different signal conditions and application requirements.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The invention changes the filter parameter (group delay) from a static value to a variable parameter that can be adjusted. By modifying the filter's group delay characteristic, the system achieves better power efficiency through effective out-of-band noise rejection while controlling the latency introduced by filtering.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11438697B2Low-latency audio output with variable group delay

Publication Date: 2022.09.06 CIRRUS LOGIC INC

AI summary

A system may include a digital delta-sigma modulator configured to receive a digital audio input signal and quantize the digital audio input signal into a quantized signal, a filter configured to receive the quantized signal and perform filtering on the quantized signal to generate a filtered quantized signal, the filter having a variable group delay, and a current-mode digital-to-analog converter configured to receive the filtered quantized signal and convert the filtered quantized signal into an equivalent current-mode analog audio signal.