Adaptive Doppler Filter Weights for Pulsed Interference
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Solution Overview
Problem
Radar systems face challenges in mitigating pulsed interference, which can lead to missed target detection and degraded detection performance due to noise levels rising above real target signal levels, especially in scenarios with multiple mobile radars or frequency congestion, where simple excision of pulsed interference can significantly degrade clutter cancellation mechanisms.
Innovation Solution
A range-gated Doppler radar system that calculates a vector of weights using a reduced overall covariance matrix and a reduced progressive phasor vector, formed by deleting rows and columns corresponding to corrupted pulses, to mitigate pulsed interference, allowing for effective ground clutter cancellation while maintaining detection performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If pulsed interference is excised from the data to prevent propagation in the frequency domain, then the interference effect is mitigated, but the clutter cancellation mechanism is significantly degraded
Solution Approach 1:
The patent introduces prediction techniques as an intermediary mechanism to generate replacement values for excised pulse returns. These predicted values serve as mediators that allow the clutter cancellation mechanism to continue functioning by providing plausible substitute data that maintains the statistical properties of the original signal, thus preventing the degradation of clutter cancellation performance while still removing the harmful interference.
Solution Approach 2:
The patent changes the parameters of the data processing system by dynamically adjusting the excision and replacement strategy based on interference detection. When pulsed interference is detected, the system modifies the covariance matrix and signal processing parameters to account for the missing data points, transforming the problem from one of data loss to one of adaptive parameter adjustment that maintains overall system performance.
2Object-generated harmful factors
If prediction techniques are used to replace missing pulse data, then some reduction of clutter return is achieved, but residual clutter remains unacceptable
Solution Approach 1:
The patent implements feedback mechanisms where the results of prediction and replacement are evaluated against actual signal characteristics. The system uses the detected interference patterns and predicted replacement values to continuously refine the clutter cancellation process, adjusting weights and parameters based on the residual error between predicted and actual signals, thereby progressively reducing residual clutter to acceptable levels.
3Object-affected harmful factors
If radar synchronization is used to eliminate pulsed interference, then interference is effectively removed, but the approach is incompatible with radar search mode and infeasible for mobile radars
Solution Approach 1:
The patent extracts the interference mitigation function from the radar synchronization mechanism, creating an independent signal processing step that operates on individual radar returns. By removing the dependency on synchronized operation between multiple radars and implementing interference detection and replacement within each radar's own signal processing chain, the solution becomes compatible with search modes and mobile operations while maintaining effectiveness against pulsed interference.
Data Source
AI summary
A range-gated Doppler radar configured to mitigate the effects of pulsed interference. A Doppler filter is constructed using a vector of weights, the vector of weights being calculated as the matrix product of (i) the inverse of an reduced overall covariance matrix and (ii) a reduced progressive phasor vector. The reduced overall covariance matrix is formed by deleting from an overall covariance matrix rows and columns corresponding to pulses corrupted by pulsed interference. The reduced progressive phasor vector is formed by deleting from a progressive phasor vector elements corresponding to pulses corrupted by pulsed interference. The elements of the progressive phasor vector have constant modulus and the phase of the elements changes linearly within the vector. The overall covariance matrix is a weighted sum of an identity matrix and several specific covariance matrices, that may represent distributed clutter with positive velocity, distributed clutter with negative velocity, and ground clutter.