Radar Sea Clutter Filtering via Scan-to-Scan Correlation
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Solution Overview
Problem
Existing methods are ineffective in filtering sea spikes from radar signals, which are indistinguishable from target signals due to their short duration and repetitive nature, leading to a high false alarm rate in marine environments, especially in rough sea conditions.
Innovation Solution
A method utilizing scan-to-scan correlation of radar information, estimating radial speed by quantizing the radar area into elementary cells, calculating phase differences, and correlating plots across scans to differentiate between target and sea clutter, employing a coherent radar system with a signal processor and memory-based correlation to refine the filtering process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional Doppler filtering is used to process radar signals, then target detection is enabled, but sea spikes cannot be distinguished from targets leading to high false alarm rates
Solution Approach 1:
The patent segments the radar signal processing into multiple independent analysis dimensions: amplitude characteristics, phase characteristics, and temporal patterns across consecutive scans. By dividing the detection problem into these separate segments, the system can evaluate each dimension independently and combine results to distinguish targets from sea spikes, thereby reducing false alarms while maintaining detection accuracy.
Solution Approach 2:
The patent transitions from conventional single-dimension amplitude-based detection to multi-dimensional analysis by incorporating phase information and temporal correlation across multiple scans. This dimensional expansion allows the system to differentiate between targets and sea spikes that appear similar in amplitude alone, resolving the contradiction between detection reliability and false alarm reduction.
2Reliability
If correlation windows are enlarged to capture potential target movements, then target tracking is improved, but the probability of including sea spikes in the windows increases reducing filtering effectiveness
Solution Approach 1:
The patent implements dynamic correlation window adjustment where the window parameters (size, position, shape) are adapted based on the specific characteristics of each detected plot and its temporal evolution. Rather than using fixed large windows that inevitably capture sea spikes, the system dynamically optimizes window parameters to tightly bound actual targets while excluding random sea clutter, thus maintaining tracking accuracy while improving filtering precision.
Solution Approach 2:
The patent changes multiple parameters simultaneously to optimize the balance between tracking and filtering: correlation threshold levels, window size parameters, scan interval selections, and amplitude/phase deviation tolerances. By adjusting these parameters based on sea state conditions and target characteristics, the system achieves both reliable tracking and precise clutter rejection without the trade-off present in fixed-parameter approaches.
3Object-generated harmful factors
If phase difference calculation is performed for all radar cells to estimate radial speed, then sea spike filtering is improved, but computational complexity increases
Solution Approach 1:
The patent segments the computational workload by first performing coarse filtering on all radar cells using simpler metrics (amplitude thresholds, basic consistency checks), then applying computationally intensive phase difference calculations only to cells that pass the initial screening and show potential target or sea spike characteristics. This segmented approach maintains sea spike detection accuracy while significantly reducing overall computational complexity compared to processing all cells uniformly.
Solution Approach 2:
The patent applies the principle of partial action by performing detailed phase-based analysis on only a subset of radar cells that are most likely to contain targets or sea spikes, rather than exhaustively processing every cell. This selective application of complex processing achieves sufficient sea spike detection accuracy while avoiding the excessive computational burden of universal detailed analysis.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Significantly reduces the probability of false alarms by creating smaller, more accurate correlation windows based on radial speed estimation, effectively distinguishing targets from sea spikes, even in high sea state conditions, while maintaining target detection accuracy.
Implementation Method 1
calculating the phase differences between echoes from subsequent sweeps and estimating the radial speed of the echoes from the phase differences
Data Source
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AI summary
The present disclosure concerns a method for the post-processing of the radar data, that uses the information of the Doppler speed as obtained by the coherent processing of the input data, to reduce the clutter due to waterbodies, in particular the sea clutter. The present disclosure further concerns a coherent radar provided with means suitable to implement the invention method.