Adaptive Beam Control for Secondary Radar Interrogation
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Solution Overview
Problem
Secondary surveillance radars face challenges in efficiently detecting and tracking aircraft, particularly near targets with high movement windows and long-range targets, due to limited beam width and high sectoral workloads, leading to increased interrogation rates and reduced radar performance.
Innovation Solution
A secondary radar system with dynamically controlled beam width, using a combination of SUM, DIFF, and CONT channels to adjust beam width based on target movement and position, reducing unnecessary interrogations and improving detection precision by pre-locating targets at the edge of the main lobe and selectively re-interrogating them for precise positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a narrow beam with high gain is used to detect long-range targets, then detection range is improved, but the number of selective interrogations increases for near targets with high movement windows
Solution Approach 1:
The patent applies dynamic beam width adjustment by switching between narrow and wide beams based on target characteristics. For near targets with high movement windows, the system uses a wide beam to reduce the number of selective interrogations. For long-range targets, it switches to a narrow beam to maintain detection precision. This dynamic adaptation resolves the contradiction between detection precision and interrogation rate.
Solution Approach 2:
The system applies different beam characteristics to different spatial regions and target types. Near targets receive wide beam illumination with reduced interrogation rates, while long-range targets receive narrow beam illumination with higher precision. This localized quality adjustment allows the radar to optimize performance for each target category simultaneously.
2Productivity
If a narrow beam is used to reduce the number of selective interrogations, then productivity is improved, but detection precision for long-range targets deteriorates
Solution Approach 1:
The radar system dynamically switches between narrow and wide beams based on real-time target assessment. When processing near targets with large movement windows, it uses wide beams to improve efficiency. When processing long-range targets, it switches to narrow beams to maintain precision. This temporal dynamics allows the system to optimize for productivity or precision depending on the operational context.
3Productivity
If the beam width is increased to cover larger movement windows, then the number of selective interrogations is reduced, but detection precision for position measurement deteriorates
Solution Approach 1:
The patent segments the detection process into two distinct phases: a wide beam phase for initial target acquisition and movement window coverage, and a narrow beam phase for precise position measurement. This segmentation allows the system to first reduce the number of interrogations using a wide beam, then switch to a narrow beam to obtain precise position data, thereby resolving the contradiction between productivity and measurement precision.
Solution Approach 2:
The system performs preliminary target acquisition and movement window assessment using a wide beam before switching to a narrow beam for precise measurement. This preliminary action with the wide beam reduces the interrogation burden, while the subsequent narrow beam phase ensures accurate position measurement, thus resolving the contradiction through sequential processing.
4Adaptability or versatility
If the radar processes high sectoral workloads with multiple aircraft, then coverage is improved, but the time available for each target is reduced
Solution Approach 1:
The radar system dynamically adjusts beam width based on the number and distribution of targets in the sector. When high sectoral workload is detected with multiple aircraft, the system uses wider beams to cover larger angular sectors, thereby reducing the number of beam positions required and increasing illumination time per target. This dynamic adaptation resolves the contradiction between coverage and time allocation.
Solution Approach 2:
The system changes the beam width parameter adaptively based on sectoral workload conditions. For high workload scenarios with multiple aircraft, it increases beam width to reduce the total number of interrogations required across the sector, thereby preserving illumination time for each individual target. This parameter change allows the system to maintain both coverage and adequate time per target.
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
This approach reduces the number of selective interrogations, limits radar time loss, and enhances detection capabilities by dynamically adapting beam width to target characteristics, improving detection precision and reducing contamination from false targets.
Implementation Method 1
an antenna having a radiating pattern forming a sum channel, called SUM, a radiating pattern forming a difference channel called DIFF and a pattern forming a control channel called CONT, means for generating at least interrogation messages on the SUM channel and ISLS signals on the CONT channel, means for transmitting these messages via the SUM channel and via the CONT channel respectively
Implementation Method 2
means for receiving and processing the signals received via the SUM, DIFF and CONT channels, configured for detecting the replies of targets on the signals received via the SUM and/or DIFF channels
Data Source
AI summary
A radar includes an antenna having a radiating pattern forming a sum channel, a radiating pattern forming a difference channel and a pattern forming a control channel, and generates at least interrogation messages on the sum channel and interrogation messages on the control channel; transmits messages via the sum channel and via the control channel respectively, and receives and processes signals received via the sum, difference, and control channels, configured for detecting replies of targets on the signals received via the sum and difference channels and carrying out monopulse processing and RSLS processing on the replies. The transmission is configured such that, for each target, the width of the beam for transmitting interrogations and receiving mode S selective replies is controlled based on the movement window of the target and position of the axis of the antenna in the window, to provide detection of the target by reducing the number of selective interrogations by a selective sub-interrogation of the target while ensuring precise positioning in azimuth: by pre-locating the target at the edge of the main reception lobe of the antenna by deviation measurement between the signals received on the difference and sum channels; and by selectively re-interrogating the pre-located target in mode S by calculation of the roll-call signal nearest to the centre of the main lobe to ensure precision in azimuth, without any other unnecessary supplementary interrogation.