Antenna Boresight Estimation via Doppler Error Minimization
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Solution Overview
Problem
Existing radar systems face challenges in accurately correcting for antenna gimbal biases, which can lead to significant errors in target location measurements, especially for ground targets, due to the high costs and limitations of factory alignment and on-aircraft calibration methods.
Innovation Solution
A system and method that estimates the antenna boresight direction by minimizing Doppler errors using a processor that receives Doppler and line-of-sight measurements, allowing for real-time correction of gimbal biases during operation, rather than relying on expensive initial calibration methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If factory alignment or on-aircraft calibration is used to correct gimbal biases, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The system performs self-calibration by using its own radar imaging capability to detect and correct gimbal biases. The processor analyzes the radar image to automatically determine pointing biases without requiring external calibration equipment or facilities, allowing the system to calibrate itself during normal operation.
Solution Approach 2:
The invention creates a virtual calibration target by generating a radar image of the ground scene. Instead of requiring physical calibration targets in anechoic chambers, the system uses the radar image itself as a reference to determine and correct gimbal biases, replacing expensive physical calibration infrastructure with computational methods.
2Manufacturing precision
If factory alignment in anechoic chambers is performed, then manufacturing precision is improved, but ease of manufacture deteriorates
Solution Approach 1:
The invention replaces mechanical calibration systems (anechoic chambers, physical alignment equipment) with a computational approach. The processor uses radar signal processing and image analysis to determine and correct gimbal biases, substituting complex mechanical calibration infrastructure with software-based solutions that can be performed in field conditions.
Solution Approach 2:
The radar imaging system serves dual purposes: it performs its primary function of ground target imaging while simultaneously functioning as a calibration tool for detecting and correcting gimbal biases. This multi-functionality eliminates the need for separate calibration equipment and facilities, simplifying the manufacturing and deployment process.
3Measurement precision
If conventional calibration methods are used, then initial biases are removed, but vibration from transportation introduces additional mechanical biases
Solution Approach 1:
The system performs dynamic calibration during actual missile flight operations rather than static calibration before deployment. The processor continuously or periodically determines and corrects gimbal biases while the system is operating, allowing the calibration to account for vibrations and mechanical stresses that occur during transportation and flight, thereby maintaining accuracy under dynamic conditions.
Solution Approach 2:
The system performs calibration action preliminarily by determining and correcting gimbal biases before they significantly degrade measurement accuracy. The processor monitors and adjusts for biases in real-time during operation, preventing the accumulation of errors that would occur if calibration were only performed initially and then left unchanged despite ongoing vibrations.
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 provides a more accurate and cost-effective method for correcting antenna pointing biases, ensuring precise target location measurements and improving missile guidance accuracy without the need for expensive initial calibration.
Implementation Method 1
receiving a Doppler measurement and a line-of-sight direction measurement corresponding with the Doppler measurement
Data Source
AI summary
A system for estimating an antenna boresight direction. The novel system includes a first circuit for receiving a Doppler measurement and a line-of-sight direction measurement corresponding with the Doppler measurement, and a processor adapted to search for an estimated boresight direction that minimizes a Doppler error between the Doppler measurement and a calculated Doppler calculated from the estimated boresight direction and the line-of-sight direction measurement. The line-of-sight direction measurement is measured relative to the true antenna boresight, and the calculated Doppler is the Doppler calculated for a direction found by applying the line-of-sight direction measurement to the estimated boresight direction. In a preferred embodiment, the first circuit receives a Doppler measurement and a line-of-sight direction measurement from each of a plurality of pixels, and the processor searches for an estimated boresight direction that minimizes a sum of squares of Doppler errors for each of the pixels.