ANC Signal Timing Layout for Predictable Low-Latency Cancellation
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Solution Overview
Problem
Active Noise Cancellation (ANC) systems face challenges in achieving low end-to-end system latency due to environmental and processing delays, which limit their ability to effectively cancel noise, especially higher frequency components, and traditional methods to reduce latency increase power consumption and complexity.
Innovation Solution
The system controls latency by using an ADC to oversample noise signals, a digital transport layer to organize and process data within a predictable sample period, and a digital signal processor to generate noise cancellation signals with a predictable delay, which is accounted for by the signal processing algorithm, incorporating a sequencing processor and optional power control for ADCs to reduce latency and power usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the sample rate is increased to reduce processing latency, then the latency is lowered, but power consumption and system complexity increase
Solution Approach 1:
The patent segments the noise cancellation processing into multiple independent filter banks, each handling specific frequency ranges. This allows parallel processing of different frequency components, reducing overall processing latency without requiring a uniformly high sample rate across all frequencies, thereby lowering power consumption.
Solution Approach 2:
The patent applies partial action by using different sample rates for different filter banks based on their specific requirements. High-frequency components that require lower latency are processed at higher sample rates, while low-frequency components can be processed at lower sample rates, optimizing the balance between latency and power consumption.
2Loss of time
If the sample rate is increased to reduce processing latency, then the latency is lowered, but system complexity and computational requirements increase
Solution Approach 1:
The patent divides the complex noise cancellation task into multiple simpler filter banks operating at different sample rates. Each filter bank processes a specific frequency range with appropriate computational complexity, avoiding the need for a single high-complexity system operating at uniformly high sample rates.
Solution Approach 2:
The patent changes the sample rate parameter dynamically across different filter banks and processing stages. By adapting the sample rate to the specific requirements of each frequency component, the system reduces overall computational complexity while maintaining necessary latency performance.
3Productivity
If down sampling is used to reduce processing requirements, then the MIPS required is lowered, but group delay is added to the circuit
Solution Approach 1:
The patent segments the signal processing into multiple filter banks that perform downsampling at different stages. By distributing the downsampling operations across parallel filter banks rather than applying a single aggressive downsampling stage, the system reduces overall group delay while maintaining processing throughput.
Solution Approach 2:
The patent performs preliminary filtering and preprocessing operations before downsampling to preserve critical signal information. This preliminary action reduces the need for aggressive downsampling that would introduce excessive group delay, allowing for more gradual rate transitions.
Data Source
AI summary
Active Noise Cancellation (ANC) systems and methods that reduce latency to improve performance. In certain embodiments the systems sample a noise signal using a sample period to create a stream of digital signal data that is representative of the noise signal. A data transport layer carries the digital signal data to a signal processor. The transport layer temporally organizes the digital signal data to place the digital signal data within an initial phase of a sample period. The remaining phase of the sample period is set to a duration that allows the signal processor to process the digital signal data carried in the initial phase and to output the processed data during the same sample period. In this way, the processing of data occurs within one sample period and the latency is reduced and predictable.