Interference Suppression Circuits for Spectrally Overlapping Signals
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Solution Overview
Problem
Existing methods for reducing interference signals that spectrally overlap with desired signals are ineffective, particularly when the interference is spectrally matched to the desired signal or has a varying envelope, leading to difficulties in separating the two, especially in communication and navigation systems.
Innovation Solution
A method and circuit that process received signals by calculating an amplitude residual and using thresholds to determine whether to apply an interference suppression algorithm, which includes applying a linear time domain filter or using non-unity power processing to reduce interference, allowing for effective separation of desired and interference signals without prior knowledge of the interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If notch filtering or frequency domain excision is used to remove interference, then narrowband interference can be suppressed, but the desired signal is removed when interference is spectrally matched to the desired signal
Solution Approach 1:
The patent segments the interference removal process into multiple domains: time domain for initial interference identification, frequency domain for spectral analysis, and I/Q domain for precise interference excision. This multi-domain segmentation allows selective interference removal while preserving the desired signal even when spectrally matched.
Solution Approach 2:
The patent introduces an intermediary detection mechanism that identifies interference characteristics before excision. By detecting interference properties (such as spectral matching conditions) as an intermediary step, the system can adaptively adjust the excision process to preserve the desired signal while removing interference.
2Object-affected harmful factors
If adaptive antenna-array is used to null out matched spectral interference, then interference can be suppressed in spatial domain, but the implementation becomes costly and incompatible with single element receivers
Solution Approach 1:
The patent extracts the interference suppression capability from complex spatial domain processing (antenna arrays) and implements it in the signal processing domain using I/Q domain excision. This extraction allows single-element receivers to achieve interference suppression without requiring multiple antennas or complex spatial processing.
Solution Approach 2:
The patent replaces the mechanical/spatial system (antenna arrays with multiple elements) with a signal processing system operating in the I/Q domain. This substitution maintains interference suppression functionality while dramatically reducing hardware complexity and making it compatible with single-element receivers.
3Object-affected harmful factors
If MLSE algorithm is used to estimate interference in presence of constant envelope interference, then interference can be reduced, but the algorithm must be customized for specific desired signal
Solution Approach 1:
The patent implements a universal interference excision algorithm that operates in the I/Q domain and can handle multiple types of desired signals (different modulations, frequencies, and formats) without requiring customization. The algorithm detects and excises interference based on its spectral characteristics rather than signal-specific properties, providing multi-functional interference suppression.
4Object-affected harmful factors
If adaptive filter is used to cancel interference from constant envelope signal, then interference cancellation is achieved, but narrow band signal buried beneath wide-band interference cannot be recovered due to frequency selective steady state transfer function
Solution Approach 1:
The patent moves the interference cancellation process from the frequency domain (where adaptive filters operate with frequency-selective transfer functions) to the I/Q domain. This dimensional change allows uniform interference excision across the entire signal bandwidth, enabling recovery of narrowband signals buried beneath wideband interference without the limitations of frequency-selective filtering.
Data Source
AI summary
Under one aspect, a method is provided for processing a received signal, the received signal including a desired signal and an interference signal that spectrally overlaps the desired signal. The method can include obtaining an amplitude of the received signal. The method also can include obtaining an average amplitude of the received signal based on at least one prior amplitude of the received signal. The method also can include subtracting the amplitude from the average amplitude to obtain an amplitude residual. The method also can include, based upon an absolute value of the amplitude residual being less than or equal to a first threshold, inputting the received signal into an interference suppression algorithm so as to generate a first output including the desired signal with reduced contribution from the interference signal.