Radar Sea Spike Filtering via Doppler Speed Estimation
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Solution Overview
Problem
Existing radar technologies are ineffective in filtering sea spikes, which are short-duration, repetitive echoes that resemble target signals, especially in high-resolution X-band radar systems, leading to false alarms and inability to distinguish between target and clutter signals.
Innovation Solution
A method that estimates the absolute radial speed of radar echoes by calculating phase differences between subsequent sweeps using a coherent radar system, subdividing the radar area into elementary cells, and averaging the radial speeds to filter out sea spikes effectively, while reducing computational load by performing calculations post-data extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional Doppler filtering is used, then target detection is enabled, but sea spikes cannot be distinguished from targets leading to false alarms
Solution Approach 1:
The invention changes the parameter used for target-clutter discrimination from amplitude characteristics to absolute radial speed. By calculating phase differences between subsequent sweeps and converting them to radial speeds, the system creates a new discrimination parameter that effectively separates sea spikes (with typical speeds of a few m/s) from true targets (with higher speeds), thereby reducing false alarms while maintaining detection accuracy
Solution Approach 2:
The invention replaces the conventional amplitude-based detection mechanism with a phase-difference-based speed estimation mechanism. Instead of relying on signal amplitude characteristics that cannot distinguish sea spikes from targets, the system uses coherent phase measurement and Doppler speed calculation to create a more reliable discrimination method
2Measurement precision
If correlation windows are made larger to improve target tracking, then tracking accuracy improves, but the probability of including sea spikes in the windows increases
Solution Approach 1:
The invention makes the correlation window dynamic by adjusting its size based on the estimated radial speed of the target. Faster targets receive larger correlation windows while slower targets (including sea spikes) receive smaller windows. This dynamic adaptation allows the system to maintain high tracking accuracy for true targets while minimizing the inclusion of sea spikes in the correlation windows
3Measurement precision
If phase difference calculation is performed for all range cells, then complete speed estimation is achieved, but computational load increases
Solution Approach 1:
The invention segments the radar processing into two stages: first, plots are extracted from detected echoes in the usual way; second, phase difference calculation and speed estimation are performed only for the extracted plots rather than for all range cells. This segmentation reduces the computational load significantly while maintaining complete speed estimation for all relevant targets
Solution Approach 2:
The invention applies partial action by performing the computationally intensive phase difference calculation only on the subset of range cells that contain extracted plots, rather than on all range cells. This partial processing approach achieves the necessary speed estimation accuracy for target discrimination while avoiding the excessive computational burden of processing all range cells
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
The method significantly reduces false alarms by an order of magnitude and improves target detection accuracy by creating smaller correlation windows based on accurate radial speed estimation, effectively filtering sea spikes without compromising target detection.
Implementation Method 1
Method for determining an estimate of the radial speed of radar echoes by using the Doppler information
Implementation Method 2
calculating the phase differences between subsequent sweeps
Implementation Method 3
transmits a signal and listens to return echoes
Implementation Method 4
the reflection of the electromagnetic Energy upon natural elements (mountains, precipitations, etc.) or artificial (buildings, architectural structures, etc.)
Data Source
Figure 1~2
Figure 3~4(b)
Figure 5
AI summary
The present disclosure concerns a method of post-processing of the radar data that uses the information of the Doppler speed obtained by the coherent processing of the input data, in order to calculate the radial speeds of the detected objects, in particular close to waterbodies. The present disclosure further concerns a coherent radar provided with means suitable to implement the method of the present disclosure.