Conversion Circuit Intermodulation Correction for Oversampled Signals
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Solution Overview
Problem
Existing conversion circuits in aircraft reception chains face challenges in achieving high dynamic performance and wideband processing due to contradictory constraints of speed/bandwidth and dynamic range, leading to intermodulation faults that are difficult to correct using traditional methods, especially when dealing with oversampled narrowband signals.
Innovation Solution
A method involving a programmable logic circuit, such as an FPGA, generates a complex correction function by calculating polynomial functions of the digital output signal, applying filters, and using Hilbert filtering to reduce intermodulation faults without generating unwanted harmonic distortion, allowing for efficient processing of high carrier and high sampling frequency signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the operating frequency is set to high ratios of the sampling frequency (e.g., f0 = fECH/5, f0 = fECH/8, f0 = 3*fECH/8), then the harmful harmonics are folded around frequencies that can be filtered, but intermodulation phenomena still create interference in the band that is not filtered
Solution Approach 1:
The patent converts the harmful intermodulation distortion into a correctable form by exploiting the property that intermodulation products appear as spectral components at specific frequencies. By using a spectral domain correction method with polynomial functions, the patent transforms the harmful intermodulation effect into a measurable and correctable spectral feature, thereby converting harm into benefit.
Solution Approach 2:
The patent introduces a spectral domain intermediary (polynomial correction function) that mediates between the raw signal containing intermodulation distortion and the corrected signal. This intermediary operates in the frequency domain to separate and correct intermodulation products without directly altering the time-domain signal, thus resolving the contradiction between filtering harmonics and eliminating intermodulation interference.
2Measurement precision
If traditional correction methods are used for intermodulation faults, then some correction can be achieved, but they are ineffective for oversampled narrowband signals and generate unwanted harmonic distortion
Solution Approach 1:
The patent transitions from time-domain correction methods to spectral-domain correction methods. By transforming the correction operation into the frequency domain using spectral analysis and polynomial functions, the patent achieves precise correction of intermodulation faults in oversampled narrowband signals while avoiding the generation of unwanted harmonic distortion that plagues traditional time-domain methods.
Solution Approach 2:
The patent changes the operational parameters of the correction method by working in the spectral domain rather than the time domain. This parameter change allows the use of polynomial functions applied to spectral components, which provides precise control over the correction process and eliminates the generation of unwanted harmonic distortion while maintaining high correction accuracy.
Data Source
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AI summary
The invention relates to a method for correcting intermodulation errors caused by a conversion circuit (14) for converting an analog input signal to a digital output signal, wherein the method comprises the steps of: - providing the digital output signal, - generating a correction function, said correction function being a complex function of the digital output signal, and - correcting the digital output signal using the correction function, to produce a corrected digital output signal.