Asynchronous Sample Rate Conversion With Adjacent-Sample Interpolation
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Solution Overview
Problem
Conventional asynchronous sampling rate converters require high-speed processing and suffer from significant calculation time and waveform distortion when converting sampling frequencies, particularly when up-sampling to the least common multiple and down-sampling, leading to amplitude reduction and potential distortion in digital signal conversion.
Innovation Solution
An asynchronous sampling frequency conversion device that calculates output sampling data using input sampling data from timings immediately before and after the desired sampling timing, based on the ratio of input and output sampling frequencies, reducing the need for extensive interpolation coefficient calculations and minimizing waveform distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional asynchronous sampling rate converter performs up-sampling to the least common multiple and then down-sampling, then sampling frequency conversion is achieved, but calculation time increases significantly and processing complexity increases
Solution Approach 1:
The patent segments the sampling frequency conversion process into direct interpolation between adjacent input samples based on timing ratios, eliminating the need for complete up-sampling to least common multiple followed by down-sampling. This segmentation approach processes only the necessary intermediate samples rather than all intermediate steps.
Solution Approach 2:
The patent applies partial action by performing only the necessary interpolation to generate output samples at the target sampling rate, rather than performing the complete up-sampling to least common multiple and subsequent down-sampling. This reduces the total number of processing operations while achieving the same frequency conversion goal.
2Device complexity
If conventional asynchronous sampling rate converter uses linear interpolation, then calculation complexity is reduced, but waveform distortion increases and amplitude accuracy decreases
Solution Approach 1:
The patent changes the interpolation parameter from fixed linear interpolation to time-ratio-based interpolation coefficients. The interpolation coefficient is calculated based on the actual time ratio between input and output sampling timings, allowing the interpolation to adapt to different frequency ratios and maintain waveform accuracy while keeping calculation complexity low.
3Reliability
If LPF with high-speed responsiveness is used in conventional asynchronous sampling converter, then high-frequency component filtering is improved, but processing performance requirements increase
Solution Approach 1:
The patent extracts and removes the need for high-speed responsive LPF by performing anti-aliasing filtering during the interpolation process itself. The filtering function is integrated into the sample value calculation rather than being a separate high-speed processing stage, thereby maintaining filtering reliability while reducing processing performance requirements.
Data Source
AI summary
An asynchronous sampling frequency conversion device includes: a storage unit configured to store input digital signals; a data specifying unit configured to specify first data and second data based on a ratio of a sampling frequency of the input digital signal to a sampling frequency of an output digital signal, the first data being sampled at a sampling timing immediately before an ith (where i is a natural number) sampling timing of the output digital signal among the input digital signals stored in the storage unit, the second data being sampled at the sampling timing immediately after the ith sampling timing of the output digital signal; and an output data value calculator configured to calculate a value of ith data of the output digital signal based on the first data and the second data specified by the data specifying unit and the ratio.