Resampling Detection Using FIR Filters for Phase Mismatch
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Solution Overview
Problem
Conventional resampling apparatuses cannot detect whether a digital signal has been resampled when the sample phases are not matched before and after the resampling process, leading to signal deterioration upon repeated downsampling and upsampling.
Innovation Solution
A resampling detection apparatus using FIR digital filters to determine if an input signal has been resampled by establishing specific conditions based on filter coefficients and boundary values, allowing for detection even when phases are not aligned, and restoring original data to suppress frequency characteristic deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional resampling apparatus is used for repeated downsampling and upsampling, then the resampling process can be performed, but the frequency characteristic of the signal deteriorates due to repeated filtering
Solution Approach 1:
The invention performs preliminary detection to identify whether the input signal has already been resampled by comparing sample phases. This preliminary action prevents unnecessary filtering operations, thereby avoiding frequency characteristic deterioration while maintaining resampling functionality.
Solution Approach 2:
Instead of applying filtering unconditionally, the invention inverts the conventional approach by detecting resampled signals and skipping the filtering process. This inversion prevents the harmful effect of repeated filtering while still enabling resampling operations.
2Reliability
If phase-matched resampling is used, then frequency characteristic can be maintained, but the method cannot be applied when sample phases are not matched before and after resampling
Solution Approach 1:
The invention changes the detection parameter from requiring phase matching to detecting phase relationships between consecutive samples. By monitoring whether the phase difference between samples remains consistent, the system can identify resampled signals regardless of absolute phase alignment, thereby maintaining frequency characteristics while adapting to phase mismatches.
3Adaptability or versatility
If resampling detection is performed without phase matching consideration, then adaptability to phase mismatches is improved, but detection accuracy decreases
Solution Approach 1:
The invention applies local quality analysis by examining the phase relationship between specific consecutive samples rather than requiring global phase matching. This localized approach maintains detection accuracy by focusing on the characteristic phase shift introduced by resampling, while being adaptable to overall phase mismatches in the signal.
Data Source
Figure 1A~1B
Figure 2A~3
Figure 4A~4B
AI summary
A resampling detection apparatus for receiving a plurality of input signals composing a digital signal, and detecting whether the digital signal is a resampled signal, includes an estimation section (303, 304) that estimates a signal before resampling for the digital signal from one or more input signals, and a detecting section (306) detects whether the digital signal is a resampled signal, using the estimated signal and one or more input signals.