Electronically Scanned Antenna Subarrays for Hybrid Clutter Suppression
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Solution Overview
Problem
Airborne radars face challenges in detecting moving targets and mapping runway environments due to high sidelobe levels in electronically scanned array antennas (ESA), leading to false or missed detections, and existing Doppler-based clutter rejection techniques are inadequate for removing all clutter.
Innovation Solution
Divide the ESA into subarrays to produce sum and difference beam power profiles, compare these profiles to accentuate signal power disparities, and apply a threshold to isolate targets of interest, using time multiplexed scans and adaptive subarray configurations to enhance clutter suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electronically scanned array antennas (ESA) are used for airborne radar, then detection capability is improved, but high sidelobe levels cause false or missed detections
Solution Approach 1:
The ESA antenna is divided into multiple subarrays, each capable of independent beamforming. This segmentation allows the system to create multiple beams (sum beam, difference beams) simultaneously, enabling discrimination between clutter and targets through comparative analysis of power profiles across different subarray configurations
Solution Approach 2:
The patent employs difference beamforming by inverting the phase relationships between subarrays. By comparing the sum beam (all subarrays in phase) with difference beams (subarrays with inverted phases), the system exploits the fact that clutter returns will have consistent phase relationships while targets will show phase variations, thereby suppressing sidelobe clutter
2Object-affected harmful factors
If Doppler based clutter rejection techniques are used, then some clutter is removed, but subtle changes in far-field beam parameters prevent complete clutter removal
Solution Approach 1:
The patent changes the spatial parameters of beamforming by adjusting subarray phase relationships to create multiple beam patterns (sum and difference beams). This allows the system to detect targets based on power profile discrepancies between beams, complementing Doppler techniques and addressing their limitation with far-field beam parameter changes
Solution Approach 2:
The patent introduces an intermediary processing stage that compares power profiles between sum and difference beams. This intermediary comparison mechanism identifies targets that Doppler alone might miss by detecting power disparities that arise from the spatial filtering characteristics of the subarray configurations
Data Source
AI summary
A system and method for distinguishing targets of interest from main lobe clutter and sidelobe clutter includes an ESA or AESA divided into subarrays. A sum beam power profile is produced via one or more scans of the subarrays, and a difference beam power profile is produced via calculations involving the subarrays. A comparison of the sum beam power profile and the difference beam power profile accentuates signal power disparities between targets of interest and clutter. A threshold is then applied to isolate targets of interest. Different difference beam power profiles may be used for elevation comparisons and azimuth comparisons. Alternatively, subarrays may be selected such that the same difference beam power profile may be used for both elevation and azimuth. Scans may be time multiplexed such that data from different scans may be used to produce the sum beam power profile, the difference beam power profile, or both.