FSK Interferer Removal via Spectral Peak Subtraction
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Solution Overview
Problem
Frequency shift keying (FSK) waveforms suffer from reduced signal-to-noise plus interference ratio (SINR) due to the absence of interferer protection, leading to a reduced transmission range in the presence of interferers.
Innovation Solution
A system and method that utilize a processor to perform window operations, fast Fourier transforms, interferer detection threshold calculations, peak identification, and inverse transforms to remove interferer signals from FSK waveforms, thereby enhancing the signal quality and transmission range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If FSK waveform is used for unencrypted radio transmission, then simplicity and ease of operation are improved, but signal-to-noise plus interference ratio (SINR) deteriorates in the presence of interferers
Solution Approach 1:
The patent extracts and removes interferer signals from the received FSK signal by identifying spectral peaks that correspond to interferers and subtracting them from the frequency domain representation of the signal. This separation of the desired FSK signal from interfering signals improves the SINR while maintaining the simplicity of FSK transmission.
Solution Approach 2:
The patent introduces an intermediary processing system that includes a fast Fourier transform (FFT) to convert the time-domain signal to frequency domain, identify interferers, and an inverse FFT to convert back to time domain. This intermediary processing chain protects the simple FSK transmission from interferers without changing the fundamental FSK modulation scheme.
2Reliability
If interferer protection is added to FSK waveform, then signal-to-noise plus interference ratio (SINR) is improved, but device complexity increases
Solution Approach 1:
The patent segments the interferer removal process into distinct operational steps: performing FFT on the received signal, identifying spectral peaks that exceed a threshold as interferers, and subtracting only those identified interferer components from the frequency domain signal. This segmented approach processes only the necessary portions of the signal rather than applying complex processing to the entire signal chain.
Solution Approach 2:
The patent changes the parameter representation of the signal from time domain to frequency domain using FFT, which enables easy identification and removal of interferers as discrete spectral peaks. After interferer removal, the signal is transformed back to time domain using inverse FFT. This parameter transformation simplifies the interferer removal operation compared to time-domain processing.
3Reliability
If spectral peaks are removed from frequency domain signal, then interferer signals are eliminated and signal quality is improved, but spectral leakage may occur
Solution Approach 1:
The patent applies partial action by removing only the specific spectral peaks that correspond to interferers, rather than applying broad spectral filtering that would remove desired signal components. The interferer detection threshold is set to identify only significant interferer peaks, leaving the rest of the spectrum intact and minimizing spectral leakage effects on the desired FSK signal.
Data Source
AI summary
A system may include a receiver, an input digitized data buffer, and a processor. The input digitized data buffer may be configured to accumulate samples of a time domain signal, s(t), from the receiver. The processor may be configured to: remove a confirmed peak from a frequency domain signal, S(f), to produce a corrected frequency domain signal, S′(f); perform an inverse fast Fourier transform to transform the corrected frequency domain signal, S′(f), to a corrected time domain signal, s′(t); perform an inverse window operation on the corrected time domain signal, s′(t), to recover original signal magnitudes; and output digitized data of the corrected time domain signal, s′(t), for signal processing.