Monopulse Bearing Correction for Radar Aperture Deviations
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Solution Overview
Problem
Radar systems with electronically controllable group antennas face significant bearing errors due to deviations from ideal aperture occupancy, particularly symmetry errors caused by failed or missing antenna elements, which affect the accuracy of monopulse bearing measurements.
Innovation Solution
A modified generalized monopulse approach is implemented, using a linear equation system to correct monopulse bearing values by accounting for known deviations in aperture occupancy and errors, with the application of arctan functions to accurately determine displacement corrections, and utilizing actual amplitude weightings and element positions to adapt monopulse calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional monopulse bearing measurement is used with ideal aperture occupancy, then bearing accuracy is high, but bearing errors increase significantly when aperture occupancy deviates from ideal due to failed or missing antenna elements
Solution Approach 1:
The patent pre-calculates correction terms C and μx,y based on the actual (possibly non-ideal) aperture occupancy before bearing measurement. By determining these correction parameters in advance using the known element positions and amplitude weightings, the system prepares compensation values that will be applied during monopulse calculation to counteract the effects of failed or missing antenna elements, thereby maintaining bearing accuracy despite aperture occupancy deviations
Solution Approach 2:
The patent introduces a feedback mechanism where the actual aperture occupancy information (including knowledge of failed or missing elements) is fed into the monopulse calculation process. The correction terms are derived from the actual antenna element status and fed back to adjust the bearing measurement, creating a closed-loop system that compensates for aperture occupancy deviations and maintains measurement precision
2Ease of manufacture
If analog beam formation with identical amplitude occupancy is used for sum and difference diagrams, then the system is simple to implement, but it cannot compensate for aperture occupancy deviations and symmetry errors
Solution Approach 1:
The patent applies different amplitude weightings to individual antenna elements based on their specific positions and status in the aperture. Instead of using identical amplitude occupancy for all elements, the system assigns local quality parameters (amplitude weightings) that account for each element's contribution, allowing compensation for failed or missing elements while maintaining overall system functionality and bearing measurement accuracy
3Measurement precision
If the aperture is divided symmetrically for monopulse calculation, then the monopulse characteristic is well-defined in the main lobe region, but symmetry errors from failed elements cause bearing errors that extend beyond the main lobe
Solution Approach 1:
The patent intentionally introduces asymmetry into the monopulse calculation by using different amplitude weightings for elements in the sum and difference channel calculations. Instead of requiring symmetric aperture division with identical weighting, the system allows asymmetric weighting that compensates for the asymmetry caused by failed or missing elements, thereby eliminating bearing errors that would otherwise result from symmetry deviations
Data Source
AI summary
A method for direction finding by means of monopulse formation in a radar system with electronically controlled group antenna and analog beam shaping of sum and difference channels, a self-test of the antenna being carried out to identify failed receiving elements, and the result of the self-test going directly into the monopulse formation and the test thereby being error corrected. The result of the self-test is converted into correction values that, independently of the antenna viewing direction, are combined with those from the sum channel signal and the difference channel signals of the antenna.