FFT Bin Shifting for Narrowband Interference Removal
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Solution Overview
Problem
Existing methods for removing narrowband interference from wideband communications signals, such as adaptive filtering and frequency domain nulling, often corrupt the desired signal, especially in high bit-rate and dense constellation scenarios, and fail when the interfering signal has similar energy to the communications signal.
Innovation Solution
The system employs a Fast Fourier Transform (FFT) to shift the interfering signal onto a nearest bin frequency, allowing for its removal by zeroing a single bin in the frequency domain, thereby minimizing distortion to the desired signal, and uses overlapping FFT blocks to improve performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If adaptive filtering is used to suppress narrowband interference, then narrowband signal suppression is improved, but desired signal corruption increases in high bit-rate and dense constellation scenarios
Solution Approach 1:
The patent segments the frequency spectrum into discrete bins using FFT, allowing selective processing of individual frequency components. By dividing the spectrum into N bins, the system can target and remove interference in specific bins without affecting other frequency regions, thus suppressing narrowband interference while preserving desired signal components in adjacent bins.
Solution Approach 2:
The patent applies local quality by performing frequency shifting and bin nulling only in the specific frequency regions where interference is detected, rather than applying uniform filtering across the entire spectrum. This localized approach ensures that interference removal is concentrated where needed while minimizing impact on the overall desired signal.
2Object-affected harmful factors
If frequency domain nulling is used to remove narrowband signals, then interference removal is achieved, but desired signal corruption increases especially in high bit-rate waveforms
Solution Approach 1:
The patent applies preliminary action by performing frequency shifting of the received signal before executing the FFT transform. This pre-shifting operation aligns the interfering signal components with specific FFT bins, ensuring that subsequent bin nulling operations will effectively remove the interference. This preliminary alignment step is crucial for achieving precise interference removal while minimizing desired signal corruption.
Solution Approach 2:
The patent utilizes parameter changes by dynamically adjusting the frequency shift amount based on the detected interferer frequency. The system calculates the optimal shift to align the interferer with the nearest bin center, and this parameter adjustment enables adaptive interference removal that maintains signal integrity across varying operational conditions.
3Device complexity
If conventional FFT-based methods are used without frequency shifting, then computational simplicity is maintained, but interference spreads across multiple bins reducing removal effectiveness
Solution Approach 1:
The patent applies preliminary action by performing frequency shifting of the received signal before executing the FFT transform. This pre-shifting operation aligns the interfering signal components with specific FFT bins, ensuring that subsequent bin nulling operations will effectively remove the interference. This preliminary alignment step is crucial for achieving precise interference removal while minimizing desired signal corruption.
Solution Approach 2:
The patent utilizes parameter changes by dynamically adjusting the frequency shift amount based on the detected interferer frequency. The system calculates the optimal shift to align the interferer with the nearest bin center, and this parameter adjustment enables adaptive interference removal that maintains signal integrity across varying operational conditions.
Data Source
AI summary
In accordance with the present invention, the system and method removes interfering signals from a communications signal and includes a Fast Fourier Transform (FFT) circuit for taking the FFT of a received signal and segmenting the signal into segments. A frequency shifting circuit can shift each segment in frequency to place an interfering signal within a single FFT band to be later substantially nulled. An inverse FFT circuit can place the segments of signals back within the time domain.