Signal Digitization Using Dual Sampling to Remove Harmonic Aliasing
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Solution Overview
Problem
Existing digitization methods of high-frequency analog signals are limited by harmonic aliasing, which restricts instantaneous dynamics to 30 or 40 dB, impacting the quality of digitized signals, especially at frequencies above 10 GHz.
Innovation Solution
The method involves performing at least two digitizations of signals at different sampling frequencies, allowing for the discrimination and elimination of harmonics by retaining only frequency components common to both provisional digitizations, thereby improving instantaneous dynamics and reducing harmonic impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If single-digitization at high sampling frequency is used, then bandwidth coverage is improved, but instantaneous dynamics deteriorates due to harmonic aliasing
Solution Approach 1:
The patent divides the digitization process into multiple separate digitizations performed at different sampling frequencies. Instead of using a single high-frequency digitization that causes harmonic aliasing, the method segments the measurement into several lower-frequency digitizations, each producing fewer spurious lines, and then combines the results to achieve both wide bandwidth coverage and high instantaneous dynamics.
Solution Approach 2:
The patent introduces an intermediary processing step that combines multiple provisional digitizations obtained at different sampling frequencies. This intermediary combination process allows the system to eliminate harmonic aliasing artifacts while preserving the wide bandwidth coverage, effectively mediating between the conflicting requirements of speed and measurement precision.
2Measurement precision
If multiple digitizations at different sampling frequencies are performed, then instantaneous dynamics is improved by eliminating harmonic aliasing, but measurement time increases
Solution Approach 1:
The patent performs preliminary digitizations at different sampling frequencies to obtain provisional results that contain information about the signal spectrum. By preparing these multiple digitizations in advance and then combining them through a systematic process, the method achieves high instantaneous dynamics without requiring excessive measurement time, as the combination process efficiently reuses the collected data.
Solution Approach 2:
The patent changes the sampling frequency parameter across multiple digitizations rather than using a fixed high sampling frequency. By varying this parameter, the system captures the same signal information under different sampling conditions, allowing harmonic aliasing to be eliminated through comparison while keeping the total measurement time reasonable through efficient data combination.
3Speed
If higher sampling frequency is used, then frequency band coverage is extended, but harmonic folding into the band increases
Solution Approach 1:
The patent extracts and eliminates the harmful harmonic components by performing multiple digitizations at different sampling frequencies and comparing the results. Frequencies that appear as spurious lines in only one of the digitizations are identified and removed, effectively taking out the harmonic folding artifacts while preserving the legitimate signal components that appear consistently across multiple digitizations.
Solution Approach 2:
The patent converts the harmful effect of harmonic aliasing into a beneficial identification mechanism. By deliberately performing digitizations at different sampling frequencies where harmonics fold into different positions, the method creates a pattern that allows easy identification and elimination of harmonic artifacts. The harm of harmonic folding is transformed into a useful signature that marks spurious lines for removal.
Data Source
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AI summary
The invention relates to a method (100) for digitizing signals within a frequency band, referred to as the useful band, comprising the following steps: - at least two digitizations (102, 104) of the signals in said useful band at different sampling frequencies to obtain two provisional digitizations for said useful band, and - obtaining (112) a final digitization for said useful band by eliminating, in one of said provisional digitizations, each frequency, or frequency line, that does not appear in the other of said provisional digitizations. It also relates to a computer program and a device implementing such a method.