Radar Cross-Range Resolution via Window Function Processing
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Solution Overview
Problem
Airborne radar systems face challenges in achieving effective cross-range resolution due to limited antenna aperture, leading to image smearing, especially when the aircraft is traveling in the direction of the antenna's main beam, and existing techniques like Doppler frequency gradient and monopulse radar are either ineffective or costly and complex.
Innovation Solution
A method and apparatus that enhance radar image resolution in the cross-range direction by scanning the antenna in multiple azimuth directions, processing reflected signals, and using a window function to calculate product functions and estimate target locations, resulting in improved map image resolution without dependence on the velocity vector direction and with reduced complexity compared to monopulse methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Doppler frequency gradient technique is used to enhance cross-range resolution, then image resolution is improved, but the technique becomes ineffective when the antenna points in the direction of the velocity vector
Solution Approach 1:
The patent changes the parameter used for resolution enhancement from Doppler frequency gradient to monopulse radar processing. This parameter change enables the system to achieve cross-range resolution improvement independently of the velocity vector direction, resolving the contradiction between resolution improvement and directional effectiveness.
2Adaptability or versatility
If monopulse radar technique is used to provide cross-range enhancement independent of direction, then adaptability is improved, but the system complexity and cost increase significantly
Solution Approach 1:
The patent uses a simplified processing approach that copies and processes the received radar signals through window function multiplication and azimuth bin offset calculation, rather than implementing the full complex monopulse radar system. This copying approach achieves similar cross-range enhancement with reduced system complexity.
3Measurement precision
If the antenna aperture area is increased to reduce beam width and improve resolution, then cross-range resolution is improved, but the physical size and weight of the radar system increase
Solution Approach 1:
The patent replaces the mechanical approach of increasing antenna aperture with signal processing techniques. By using window function multiplication and azimuth bin offset calculation in the signal processing domain, the system achieves improved cross-range resolution without physically enlarging the antenna aperture, thereby avoiding the associated weight increase.
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 provides enhanced radar image resolution independently of the aircraft's velocity direction and offers cost savings over monopulse techniques, effectively improving the identification of ground features and reducing image smearing.
Implementation Method 1
Airborne radar is used in aircraft navigation to generate a radar map of the ground in the vicinity of the aircraft
Implementation Method 2
One commonly used technique uses the gradient in Doppler frequency across the antenna's main beam to sharpen the image
Data Source
AI summary
Methods and apparatus for enhancing the resolution of a radar image in the cross-range direction. An example method includes receiving a plurality of received power samples in the cross-range dimension as the radar antenna scans and calculating a window function from the antenna beam response pattern. Then for each of a plurality of positions of the window function along the azimuth axis, multiplying the received response pattern by the window function at that position, yielding a product function for each position. Finally, the method includes calculating an estimated azimuth bin offset, resulting estimated target location, and a reflected power value corresponding to the integral of the product function from the product function of each position. A reconstructed azimuth bin array developed from the estimated target locations and reflected power values is substituted for the original received cross-range received power values, yielding a resolution-enhanced map image.