Airborne Radar Antenna Pointing Optimization
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Solution Overview
Problem
Airborne radars operating at high altitudes face challenges in maintaining continuous coverage of a ground area without discontinuity in detection, as existing methods fail to accurately account for radar range limitations and beam aperture variations, leading to underestimated or overestimated swath widths and non-contiguous sub-swaths.
Innovation Solution
A method that calculates the antenna elevation and pointing distances to optimize sub-swath coverage by using a criterion that accounts for atmospheric losses, antenna gains, and radar waveforms, ensuring continuous detection with minimal overlap between pointing operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a purely geometrical approach using the 3 dB aperture is used to calculate sub-swath positions, then the calculation is simple, but the estimation of the actually usable swath is falsified and continuity of detection cannot be ensured
Solution Approach 1:
The patent changes the parameter used for swath calculation from a fixed geometrical 3 dB aperture to a dynamic effective aperture that varies with distance. The effective aperture is calculated based on the radar range equation, taking into account atmospheric losses, antenna gains, and minimum detectable signal levels at different distances, thereby accurately reflecting the actually usable swath width at each range
2Ease of operation
If the beam aperture width at 3 dB is used at short distances, then the calculation is straightforward, but the swath width is underestimated
Solution Approach 1:
The patent applies dynamics by making the effective aperture a dynamic parameter that changes with distance from the radar. Instead of using a fixed 3 dB beam width, the effective aperture is continuously adjusted based on the radar range equation, atmospheric conditions, and target detectability requirements at each specific distance, ensuring accurate swath width estimation across the entire range
3Area of stationary object
If multiple pointing operations are performed to cover the area of interest, then the coverage is improved, but the number of operations increases and overlap becomes excessive
Solution Approach 1:
The patent applies preliminary action by pre-calculating the effective aperture and usable swath width at each distance using the radar range equation before performing pointing operations. This allows the system to determine the optimal number and positioning of pointing operations in advance, ensuring continuous coverage with minimal overlap by knowing exactly how far each pointing operation will effectively cover
4Device complexity
If the geometrical criterion is used to estimate swath width, then the method is simple to implement, but the limit of the radar range is not taken into account and the swath is overestimated at great distances
Solution Approach 1:
The patent applies feedback by using the radar range equation to continuously evaluate the actual detectability of targets at different distances. The effective aperture is adjusted based on feedback from atmospheric loss models, antenna gain patterns, and minimum detectable signal levels, ensuring that the estimated swath width accurately reflects the radar's actual capability at each range, preventing overestimation at great distances
Data Source
AI summary
A method for optimizing the elevational pointing of an antenna of an airborne radar system at an altitude h includes an antenna and processing and calculation means, the method comprising: a. selecting an area of interest b. calculating atmospheric losses Lref at a reference altitude href at the reference range Dref and calculating a reference criterion Kref=−40 log10 (Dref); c. for each possible elevational pointing distance of the antenna Dpt from the area of interest, calculating the antenna elevation S that makes it possible to target the distance Dpt via the centre of the antenna; d. for each distance D from the region of interest, calculating the angle θ at which the antenna observes the point of the ground at the distance D and calculating a criterion; 1. K(D)=Ge(θ)+Gr(θ)−40 log10 D+Lref(href,Dref)−Latmo(h,D) 2. where Ge(θ),Gr(θ) are respectively the gains of the antenna that are normalized at emission and at reception; e. calculating all of the distances D that, for this pointing distance Dpt, satisfy the relationship K(D)>Kref so as to obtain the start and the end of the sub-swath actually able to be used by the radar system; and calculating the actually usable sub-swaths that are to be juxtaposed (A, B, C) in order to cover the whole of the area of interest without discontinuities.