Acoustic Signal Bandwidth Extension via Frequency Shifting
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Solution Overview
Problem
Conventional telephone connections have limited bandwidth, leading to reduced speech quality due to missing high and low frequency components, and existing bandwidth extension methods introduce significant signal delay and artifacts.
Innovation Solution
A method that shifts the received acoustic signal at upper frequencies to create an upper extension signal, reducing signal processing delay by avoiding block-based processing, and optionally adds a lower extension signal using non-linear characteristics to enhance speech quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If block-based processing is used to generate bandwidth extension signals, then the extension signal can be generated with proper spectral characteristics, but significant signal delay is introduced
Solution Approach 1:
The patent segments the bandwidth extension task into two parts: using block-based processing only for generating the base extension signal from the narrowband signal, then using continuous time-domain filtering for the final signal combination. This segmentation allows the delay-critical path to use efficient filtering while the computationally-intensive spectral analysis is confined to block processing.
Solution Approach 2:
The patent performs preliminary block-based processing to generate the base extension signal and its filter coefficients in advance, then uses these pre-computed values in continuous real-time filtering. This preliminary action separates the heavy computation from the time-critical signal combination, reducing overall delay.
2Manufacturing precision
If broadband codecs are used to increase bandwidth, then speech quality improves, but new standards and complex coding/decoding methods are required at both transmitter and receiver
Solution Approach 1:
The patent extracts only the essential spectral envelope information from the narrowband signal using block-based analysis, then uses this extracted information to generate the extension signal. This extraction approach avoids the need for complete broadband coding while still achieving bandwidth extension, significantly reducing device complexity.
Solution Approach 2:
The patent introduces a time-domain filter as an intermediary between the narrowband signal and the extension signal. This filter mediates the combination of signals while maintaining spectral accuracy, avoiding the need for complex broadband codec implementations at both ends of the communication channel.
3Adaptability or versatility
If bandwidth extension is performed only on the receiver side, then existing telephone connections can be used without modification, but the system must work with severely bandwidth-limited input signals
Solution Approach 1:
Instead of trying to preserve and transmit all frequency components (the conventional approach), the patent inverts the problem by generating the missing high-frequency components from the available low-frequency components through spectral analysis and time-domain filtering. This inversion allows recovery of information that was never transmitted.
Solution Approach 2:
The patent replaces the mechanical/transmission-based approach of sending all frequency components through the channel with a signal processing approach that reconstructs missing components at the receiver. This substitution uses computational methods to compensate for the physical limitations of the transmission medium.
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 method effectively extends the bandwidth of acoustic signals with reduced delay and improved speech quality by shifting the signal and adding missing frequency components, while minimizing artifacts and maintaining compatibility with existing telephone connections.
Implementation Method 1
shifting the received acoustic signal at least above a predetermined lower frequency value and/or below a predetermined upper frequency value by a predetermined shifting frequency value to obtain the shifted signal
Data Source
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AI summary
The invention is directed to a method and an apparatus for providing an acoustic signal with extended bandwidth comprising providing an upper extension signal for extending a received acoustic signal at upper frequencies, wherein providing the upper extension signal comprises shifting the received acoustic signal at least above a predetermined lower frequency value and/or below a predetermined upper frequency value by a predetermined shifting frequency value to obtain a shifted signal.