Echo Cancellation FIR Coefficient Setting With Adaptive Impulse Level
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Solution Overview
Problem
Existing echo prevention circuits in communicating devices, such as mobile phones, face challenges in canceling echoes with high precision due to the difficulty in determining the proper magnitude of the impulse required for accurate impulse response acquisition, which is affected by variations in earphone microphone impedance, speaker sensitivity, and circuit components.
Innovation Solution
A filter coefficient setting apparatus and method that adjusts the magnitude of the impulse signal to acquire proper impulse responses, allowing for precise setting of FIR filter coefficients in an echo preventing circuit, ensuring effective echo cancellation by combining signals from both paths of the differential amplifying circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a predetermined magnitude impulse is generated for impulse response acquisition, then the impulse response can be obtained, but the precision of impulse response measurement is degraded when the magnitude is too small or overflow occurs when too large
Solution Approach 1:
The patent applies dynamics by making the impulse magnitude adjustable rather than fixed. The impulse generating unit can change the magnitude of the impulse signal based on feedback from the impulse response magnitude detection, allowing the system to adapt to different device configurations and achieve optimal measurement precision without overflow or noise degradation.
Solution Approach 2:
The patent implements feedback by detecting the magnitude of the acquired impulse response and using this information to adjust the impulse magnitude for subsequent acquisitions. This closed-loop approach ensures that the impulse magnitude is optimized for each specific device configuration, resolving the contradiction between measurement precision and acquisition reliability.
2Measurement precision
If the impulse magnitude is increased to improve signal level, then the impulse response magnitude increases, but the impulse response overflows in the AD converter
Solution Approach 1:
The patent applies preliminary anti-action by preemptively adjusting the impulse magnitude to prevent overflow before it occurs. The system detects the impulse response magnitude and uses this information to set an appropriate impulse magnitude that raises the signal level sufficiently for accurate measurement while staying below the overflow threshold of the AD converter.
Solution Approach 2:
The patent makes the impulse magnitude dynamic rather than static. The impulse generating unit adjusts the magnitude based on feedback from impulse response detection, allowing the system to optimize the signal level for each device configuration without causing overflow, thus resolving the contradiction between improving signal level and preventing overflow.
3Object-generated harmful factors
If the impulse magnitude is decreased to prevent overflow, then the impulse response overflow is avoided, but the signal level becomes too small and precision is degraded by background noises
Solution Approach 1:
The patent implements feedback by detecting the magnitude of the impulse response and using this information to adjust the impulse magnitude for subsequent acquisitions. This ensures that the impulse magnitude is sufficient to produce a high-level impulse response that exceeds background noise, while the preliminary anti-action prevents overflow by not making the impulse too strong.
Solution Approach 2:
The patent makes the impulse magnitude dynamic, adjusting it based on feedback from impulse response detection. This allows the system to optimize the signal level for each device configuration, ensuring it is high enough for accurate measurement but not so high as to cause overflow, thus resolving the contradiction between preventing overflow and maintaining precision.
4Ease of manufacture
If the filter coefficients are set based on impulse response with improper magnitude, then the filter coefficients can be obtained, but the echoes cannot be canceled effectively
Solution Approach 1:
The patent implements feedback by detecting the magnitude of the impulse response and using this information to adjust the impulse magnitude before setting the filter coefficients. This ensures that the impulse response has proper magnitude for accurate filter coefficient calculation, which in turn ensures effective echo cancellation, resolving the contradiction between ease of manufacture and reliability.
Solution Approach 2:
The patent applies preliminary action by adjusting the impulse magnitude before acquiring the impulse response used for filter coefficient setting. This preliminary adjustment ensures that the impulse response has the proper magnitude for accurate filter coefficient calculation, preventing the need for rework and ensuring effective echo cancellation from the start.
Data Source
AI summary
Echo preventing circuit includes first and second FIR filters. The outputs of the first and second FIR filters are converted into first and second analog signals. An input/output terminal outputs the first analog signal or receives a third analog signal. An AD converter converts an analog signal obtained by subtracting the second analog signal from a signal formed by combining the first analog signal and the third analog signal. A response signal acquiring unit acquires a first response signal from an output of the first FIR filter to an output of the AD converter. A filter coefficient setting unit sets the filter coefficients of the second FIR filter based on the first response signal and sets the filter coefficients of the first FIR filter based on second response signal of a section from and output of the second FIR filter to an output of the AD converter.