Single-Sideband RF Sampling to Prevent Spectrum Overlap
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Solution Overview
Problem
Conventional bandpass sampling methods face challenges with frequency overlap during down-conversion of multiple RF signals, requiring high sampling frequencies that increase the processing burden and cost of ADCs and digital signal processing.
Innovation Solution
The method involves converting RF bandpass signals into single-sideband signals using a Hilbert transformer before bandpass sampling, allowing for lower sampling frequencies and reducing the risk of spectrum overlap by removing either the upper or lower sideband spectrum, thereby determining a common effective sampling frequency domain and minimizing the sampling frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional bandpass sampling is used to down-convert multiple RF signals, then frequency down-conversion is achieved, but spectrum overlap occurs and high sampling frequencies are required
Solution Approach 1:
The patent segments the double-sideband RF signal into two separate single-sideband signals by removing either the upper or lower sideband spectrum. This segmentation prevents spectrum overlap during down-conversion, as each single-sideband signal occupies a distinct frequency range, eliminating the need for high sampling frequencies to avoid aliasing between overlapping spectra.
Solution Approach 2:
The patent applies asymmetry by converting symmetric double-sideband signals into asymmetric single-sideband signals. By retaining only one sideband (either upper or lower) and eliminating the other, the signal becomes asymmetric in the frequency domain, which prevents the spectral symmetry that causes overlap during bandpass sampling and down-conversion of multiple RF signals.
2Reliability
If high sampling frequencies are used for bandpass sampling of multiple RF signals, then spectrum overlap is avoided, but ADC performance requirements and processing costs increase
Solution Approach 1:
The patent performs preliminary action by converting RF bandpass signals into single-sideband signals before bandpass sampling. This pre-processing step removes one sideband spectrum in advance, ensuring that subsequent sampling operates on non-overlapping spectral content. As a result, lower sampling frequencies satisfy the Nyquist criterion, reducing ADC performance requirements and associated costs.
3Ease of operation
If double-sideband RF signals are sampled directly, then sampling process is simple, but spectrum overlap occurs during down-conversion
Solution Approach 1:
The patent extracts and removes one sideband spectrum from the double-sideband RF signal, keeping only the necessary single sideband for information transmission. This extraction eliminates the redundant sideband that would cause spectrum overlap during down-conversion, preventing information loss while maintaining sampling process efficiency.
Data Source
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AI summary
The present invention provides a method of bandpass sampling which particularly includes the single-sideband signal conversion procedure prior to the sampling process in the purpose of lowering the required sampling frequency. Conversion of the bandpass RF signal into a single-sideband spectrum signal which has the spectrum components only in either the positive or the negative frequency domain is accomplished by bandpass-filtering, or more effectively by using a Hilbert transformer. This invention includes a method of finding the minimum sampling frequency for simultaneous frequency down-conversion of multiple RF bandpass signals. It is expected from this invention that the components additionally required in the RF receiver due to the proposed bandpass sampling method is the bandpass filters or the Hilbert transformer for single-sideband conversion, but the benefits from this invention could be the reduced ADC speed performance and the subsequent digital processing load in the receiver system because of the reduced data rates.