CFAR Radar Control Using Segmented Annuli for Sea Clutter
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Solution Overview
Problem
Existing radar systems face challenges in accurately controlling false alarms in sea clutter due to variations in wind and ocean currents, which affect clutter characteristics and require a balance between sample size and area to estimate false alarm rates effectively.
Innovation Solution
A two-threshold detection process is implemented in the radar apparatus, with the first threshold set to achieve a measurable false alarm rate using a variable factor α1, and a second threshold using α2 derived from a look-up table based on radar parameters and clutter models, allowing for rapid adaptation to changing conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If samples are taken from a large area to estimate false alarm rate, then the false alarm rate measurement is more accurate, but local control of the threshold multiplier is lost
Solution Approach 1:
The monitoring area is divided into multiple annuli (concentric rings) centered on the radar. Each annulus independently estimates false alarm rates and controls its own threshold multiplier, enabling both local adaptation and sufficient sample size for accurate measurement.
2Adaptability or versatility
If samples are taken from a small area to enable local control, then local control of threshold multiplier is achieved, but false alarm rate estimation becomes inaccurate
Solution Approach 1:
The radar surveillance area is segmented into multiple annuli with increasing radial distances. Each annulus is large enough to provide sufficient samples for accurate false alarm rate estimation, yet distinct enough to allow local control of threshold multipliers adapted to specific clutter conditions in each region.
3Adaptability or versatility
If the number of CFAR annuli is increased to accommodate range variations, then adaptability to different clutter conditions is improved, but the false alarm rate measurement accuracy is reduced
Solution Approach 1:
Multiple annuli are created to cover different radar ranges, with each annulus optimized to contain sufficient samples for accurate measurement. The segmentation allows the system to adapt to range-dependent clutter variations while maintaining measurement accuracy within each annulus.
Solution Approach 2:
The problem is solved by introducing a radial dimension with multiple annuli at different distances from the radar. Each annulus operates independently with its own false alarm rate measurement and threshold control, allowing adaptation across the range dimension without sacrificing measurement precision in any individual annulus.
Data Source
Figure 1~2
AI summary
A method of analysing return signals of successive range cells in a scene using constant false alarm rate adaptive control comprising, for each successive range cell in turn: processing mathematically the return signal averaged over a predetermined number of cells near that cell, a first variable factor and the return signal for that cell, to derive a first result; adapting the first variable depending upon that first result; deriving a second variable factor in accordance with a predetermined relationship between the first and second factors; processing mathematically the second factor, the second averaged return signal and the return signal for the said cell, to derive a second result; and using the second result as an indication of the presence of an object of interest in the scene.