Polar Interference Cancellation for Constant-Envelope Signal Overlap
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Solution Overview
Problem
Existing methods for reducing constant envelope interference signals are complex, require customization for specific signals, and are inefficient in handling high power interference overlapping with low power desired signals, especially in crowded radio spectra.
Innovation Solution
A system and method that processes time-domain signals in rectangular coordinates, converting them to polar coordinates to estimate and subtract the interference magnitude, thereby reducing the interference power without requiring detailed knowledge of the signals, using simpler hardware and fewer processing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If maximum likelihood sequence estimation (MLSE) is used to reduce constant envelope interference, then interference reduction effectiveness is improved, but device complexity and customization requirements increase
Solution Approach 1:
The patent uses a simplified copy of the interference signal model rather than full MLSE. Instead of implementing the complete maximum likelihood sequence estimation algorithm, the invention creates a practical approximation that copies the essential interference cancellation functionality while using standard signal processing operations that are already available in typical receivers, eliminating the need for specialized MLSE hardware
Solution Approach 2:
The invention develops a universal interference reduction method that works across different signal types and scenarios without requiring customization. The approach uses general-purpose signal processing operations (FFT, magnitude calculation, phase preservation) that can handle various constant envelope interference situations, making the system adaptable to multiple applications without hardware changes
2Reliability
If adaptive filter is used to cancel interference, then interference cancellation capability is improved, but convergence time and signal recovery limitations increase
Solution Approach 1:
The patent performs preliminary transformation of the received signal into polar coordinates before interference cancellation. By converting to polar coordinates and calculating magnitudes in advance, the system prepares the signal in a form that enables immediate interference estimation and subtraction, eliminating the need for adaptive convergence time and providing instant interference cancellation capability
Solution Approach 2:
The invention replaces the adaptive filter mechanism with a direct mathematical transformation approach. Instead of using an adaptive filter that requires iterative adjustment and convergence, the patent substitutes a deterministic process involving polar coordinate transformation, magnitude calculation, and direct subtraction, which eliminates the mechanical adaptive adjustment process and its associated convergence time
3Loss of time
If FFT-based interference excision is used, then convergence time requirements are reduced, but computational complexity increases
Solution Approach 1:
The patent extracts only the essential components needed for interference cancellation from the full FFT-based approach. Instead of implementing complete spectral analysis and excision, the invention extracts just the magnitude information from polar coordinates, subtracts the interference magnitude, and reconstructs the signal, taking out only the necessary operations while eliminating computationally intensive steps
4Reliability
If successive interference cancellation or joint demodulators are used, then interference mitigation capability is improved, but signal type requirements and algorithm updates increase
Solution Approach 1:
The patent uses a simplified copying approach where the interference signal is estimated and subtracted without requiring demodulation or detailed knowledge of the interference signal type. The method copies the essential interference cancellation function while avoiding the complexity of signal-specific demodulators, making it universally applicable to different signal types
Solution Approach 2:
The invention creates a universal interference reduction system that works with various signal types without requiring specific demodulators or algorithm updates. The polar coordinate transformation and magnitude-based cancellation approach is signal-type agnostic, providing multi-functional capability that handles different modulation schemes and signal formats with the same core algorithm
Data Source
AI summary
Systems and methods are provided for processing a time-domain signal in rectangular coordinates. The signal can include a low power desired signal and a high power, approximately constant envelope interference signal that spectrally overlaps the desired signal. A rectangular to polar converter can obtain magnitude and phase of the time-domain signal in polar coordinates. An interference estimator can estimate a magnitude of the interference signal based on the magnitude of the time-domain signal in polar coordinates. A subtractor can obtain a difference magnitude in polar coordinates based on the magnitude of the time-domain signal and the estimated magnitude of the interference signal in polar coordinates. A polar to rectangular converter can obtain the desired signal with reduced power of the interference signal based on the difference magnitude and phase of the time-domain signal in polar coordinates.