TDD Hum Noise Cancellation Using DSP Correlation

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Solution Overview

Problem

Audio systems in mobile devices face challenges in handling time division duplex (TDD) hum noise due to non-linearities in audio circuitry, which affects audio quality and is exacerbated by the complexity of supporting various audio sources and sampling rates.

Innovation Solution

A method and system for TDD hum noise cancellation using a digital signal processing (DSP) algorithm that correlates the received audio signal with a TDD envelope signal, adjusts the amplitude and delay of a feedback signal, and cancels the noise using a least mean square (LMS) filter, either within a chip or with external components like capacitors and inductors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If audio circuitry is used for TDD operations in mobile devices, then audio processing capability is provided, but TDD hum noise is generated due to non-linearities

Engineering Contradiction:

Improveaudio processing capabilityVSAvoidTDD hum noise

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies noise cancellation technology that uses the harmful TDD hum noise signal itself as a reference to generate an anti-noise signal. The noise signal is captured through the microphone, processed to create a cancellation signal, and fed back through the speaker to destructively interfere with and eliminate the harmful hum noise, effectively converting the harmful factor into a beneficial noise cancellation mechanism.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The system implements feedback by capturing the TDD hum noise through the microphone, processing it through signal generation circuitry, and feeding the processed noise signal back through the speaker to cancel the original noise. This closed-loop feedback mechanism continuously monitors and adjusts to eliminate the harmful noise while maintaining audio processing capabilities.

Inventive Principle:

Principle #23Feedback

2Adaptability or versatility

If multiple audio sources and sampling rates are supported, then adaptability is improved, but device complexity increases

Engineering Contradiction:

Improvesupport for diverse audio sourcesVSAvoidprocessing circuitry complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent implements a universal audio processing system where a single set of processing circuitry can handle multiple audio sources and sampling rates. The noise cancellation mechanism is designed to work across different audio configurations, allowing the same circuitry to process various audio types (polyphonic ringers, voice, music) and sampling rates without requiring separate dedicated circuits for each type, thereby reducing overall device complexity while maintaining adaptability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS8369252B2Method and system for time division duplex hum noise cancellation

Publication Date: 2013.02.05 AVAGO TECHNOLOGIES INTERNATIONAL SALES PTE LTD

AI summary

Methods and systems for TDD hum noise cancellation are disclosed and may include correlating a received audio signal to a time division duplexed (TDD) envelope signal, controlling a feedback signal based on the correlating, and cancelling a TDD noise signal via the feedback signal. The amplitude and delay of the feedback signal may be configured for controlling. A least mean square (LMS) filter may be utilized for the correlating and may include a finite impulse response filter. The TDD envelope signal may be generated on the chip or may be received from a source external to the chip. The feedback signal may be added to the received audio signal for the cancelling.