Echo Prevention Circuit Dynamic Gain Adjustment
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Solution Overview
Problem
Existing echo prevention circuits in communication devices, such as mobile phones, face challenges in accurately canceling echo due to the vulnerability of impulse responses to circuit noises and background noises, leading to inaccurate filter coefficient settings and ineffective echo cancellation.
Innovation Solution
An echo prevention circuit with a digital signal processor (DSP) that adjusts gain levels before and after acquiring impulse responses to ensure accurate impulse response acquisition, using a subtracting circuit and amplification circuits to generate and amplify signals effectively, allowing for precise filter coefficient setting and echo cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a small impulse is used to acquire impulse responses, then the vulnerability to circuit noises and background noises is reduced, but the impulse responses become vulnerable to circuit noises and background noises making accurate acquisition difficult
Solution Approach 1:
The patent changes the gain parameter of the amplification circuit dynamically. During impulse response acquisition, the gain is set to a first gain value that prevents overflow in the AD converter while maintaining sufficient signal level. This parameter adjustment resolves the contradiction by allowing accurate impulse response acquisition without being overwhelmed by noises.
Solution Approach 2:
The amplification circuit's gain is made dynamic rather than fixed. The system switches between a first gain during impulse response acquisition and a second gain during normal operation. This dynamic adjustment allows the system to adapt to different operational requirements, achieving both accurate measurement and effective echo cancellation.
2Object-affected harmful factors
If the impulse is increased to reduce vulnerability to circuit noises and background noises, then the impulse responses will overflow in the AD converter
Solution Approach 1:
The patent adjusts the gain parameter of the amplification circuit to an optimal first gain value during impulse response acquisition. This parameter change ensures that the impulse signal is strong enough to overcome circuit noises and background noises, yet not so strong as to cause overflow in the AD converter, thus resolving the contradiction.
3Ease of operation
If the weak signal from the earphone microphone is amplified by about 50 dB, then the signal can be output effectively, but the impulse generated during impulse response acquisition is also amplified making accurate acquisition difficult
Solution Approach 1:
The amplification circuit's gain is made dynamic with two distinct states: a first gain during impulse response acquisition and a second gain (approximately 50 dB) during normal signal output. This dynamic switching resolves the contradiction by providing high amplification when needed for effective output while using lower amplification during accurate measurement phases.
Solution Approach 2:
The system performs impulse response acquisition before normal operation with high amplification. By acquiring impulse responses when the amplification is at the first gain level (before switching to the second gain), the system ensures accurate measurement of the acoustic path characteristics without the interference of excessive amplification.
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 solution enables highly accurate impulse response acquisition and effective echo cancellation by adjusting gain levels, improving the accuracy of filter coefficients and reducing the impact of circuit noises and background interference.
Implementation Method 1
a first DA converter that converts the second digital signal into a first analog signal and outputs the first analog signal; a second DA converter that converts the third digital signal into a second analog signal and outputs the second analog signal
Implementation Method 2
an amplification circuit that amplifies the signal output from the subtracting circuit and outputs the amplified signal
Implementation Method 3
an AD converter that converts the signal output from the amplification circuit into a digital signal and outputs the digital signal
Implementation Method 4
a subtracting circuit that outputs a fourth analog signal acquired by subtracting the second analog signal from a signal generated by combining the first analog signal and the third analog signal
Data Source
AI summary
An echo prevention circuit includes a filter that receives a first digital signal and outputs second and third digital signals; first and second DA converter that convert the second and third digital signals into first and second analog signals respectively; a circuit to subtract the second analog signal from a signal generated by combining the first analog signal and a third analog signal, a circuit to amplify the signal from the subtracting circuit; an AD converter that converts the amplified signal into a digital signal; a responsive signal acquiring unit to acquire a first response signal from the input of the first DA converter to the output of the AD converter and to acquire a second response signal from the input of the second DA converter to the output of the AD converter; and a unit to set filter coefficients based on the first and second response signals.