Noise Cancellation Signal Polarity Selection for Phase-Correct Output

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Solution Overview

Problem

Conventional active noise control systems face issues with signal inversion, leading to constructive interference due to multiple amplification stages, which prevents effective noise cancellation.

Innovation Solution

A signal processing apparatus incorporating an inverting circuit and a selecting circuit to determine the polarity of the noise cancellation signal, ensuring it is either inverted or non-inverted to achieve destructive interference, along with a filtering circuit to generate the appropriate noise cancellation signal.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If multiple amplifying stages are used to process the analog noise cancellation signal, then signal gain is improved, but the signal polarity is inverted multiple times causing constructive interference with noise

Engineering Contradiction:

Improvesignal gainVSAvoidnoise cancellation effectiveness

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent applies inversion by introducing a polarity selection mechanism that can deliberately invert the noise cancellation signal when needed. The inverting circuit and selecting circuit work together to ensure the output signal has the correct polarity for destructive interference, effectively using inversion as a controlled solution to the polarity problem caused by multiple amplification stages.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the polarity parameter of the noise cancellation signal dynamically. By using the selecting circuit to choose between inverted and non-inverted signals based on the number of amplification stages, the system adapts the signal polarity parameter to maintain destructive interference effectiveness regardless of the amplification path taken.

Inventive Principle:

Principle #35Parameter changes

2Power

If the analog noise cancellation signal is processed through multiple amplifying stages, then signal strength is increased, but phase relationship with noise is disrupted leading to constructive interference

Engineering Contradiction:

Improvesignal strengthVSAvoidphase control

Core Design Contradiction:

PowerVSEase of operation

Solution Approach 1:

The patent implements a feedback mechanism where the system monitors the amplification path taken by the noise cancellation signal and uses this information to control the polarity selection. The selecting circuit receives feedback about the signal processing path and automatically adjusts the polarity to ensure correct phase relationship with the noise, making phase control automatic and reliable.

Inventive Principle:

Principle #23Feedback

3Device complexity

If conventional circuit architecture is used without polarity selection, then device complexity is reduced, but noise cancellation function fails due to uncontrollable signal inversion

Engineering Contradiction:

Improvecircuit architectureVSAvoidnoise cancellation function

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent makes the noise cancellation system universal by designing it to work reliably regardless of the amplification path configuration. The polarity selection mechanism allows the same circuit architecture to adapt to different signal processing scenarios, whether the signal passes through one or multiple amplification stages, ensuring consistent noise cancellation performance across different operating conditions.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The apparatus effectively provides noise cancellation by ensuring the noise cancellation signal is in the proper phase, preventing constructive interference and enhancing noise reduction.

Implementation Method 1

The inverting circuit is employed for inverting a first signal to generate an inverted first signal

Methodology Applied

Scientific EffectSignal inversion:

Implementation Method 2

The selecting circuit is coupled to the inverting circuit, and employed for selecting one of the first signal and the inverted first signal as an output signal

Methodology Applied

Scientific EffectSignal selection:

Implementation Method 3

By superposition of the sound wave, the noise source and the anti-noise destructively interfere with each other, thereby eliminating the noise

Methodology Applied

Scientific EffectDestructive interference: Interference

Data Source

PatentUS9161127B2Signal processing apparatus

Publication Date: 2015.10.13 REALTEK SEMICON CORP

AI summary

A signal processing apparatus for generating a noise cancellation signal in accordance with a noise signal includes an inverting circuit and a selecting circuit. The inverting circuit is employed for inverting a first signal to generate an inverted first signal. The selecting circuit is coupled to the inverting circuit, and employed for selecting one of the first signal and the inverted first signal as an output signal.