Monopulse Antenna Phase Alignment Error Correction
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Solution Overview
Problem
Monopulse antenna systems often incorrectly assume an object is within the mainlobe when it is actually in a sidelobe, leading to tracking issues due to high sidelobe gains and poor signal-to-noise ratio performance, especially at large target ranges.
Innovation Solution
Implementing a mainlobe detection process that transitions from open-loop scanning to closed-loop scanning using power-level and track-lock tests, followed by hybrid tracking that combines magnitude-only and phase tracking to ensure accurate alignment and correct phase errors, thereby ensuring the object is within the mainlobe for tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If open-loop GPS tracking is used to initially point the antenna in the general direction of the object, then the system can establish coarse tracking, but the antenna may incorrectly assume it is pointing directly at the object when it is actually within a sidelobe
Solution Approach 1:
The patent performs preliminary mainlobe detection tests (power-level test and track-lock test) before establishing closed-loop tracking. This preliminary action ensures the object is within the mainlobe before committing to tracking, preventing the antenna from incorrectly tracking objects in sidelobes while maintaining the ease of open-loop initial acquisition
2Productivity
If the system relies on modem lock signal as an indicator of tracking, then the system can establish tracking indication, but the modem lock can be established even when the object is positioned within the antenna's sidelobe due to adequate SNR
Solution Approach 1:
The patent introduces mainlobe detection feedback through power-level testing and track-lock testing that continuously verify the object remains within the mainlobe. This feedback mechanism distinguishes between legitimate mainlobe tracking and false sidelobe lock, ensuring reliable mainlobe tracking while maintaining efficient tracking indication
3Productivity
If phase tracking is performed without correcting phase-alignment errors, then the system can perform tracking operations, but phase errors between the monopulse antenna system and the comparator network cause incorrect tracking
Solution Approach 1:
The patent performs preliminary phase alignment correction by detecting and correcting phase-alignment errors between the monopulse antenna system and the comparator network before initiating phase tracking. This preliminary correction ensures accurate phase relationships, enabling precise tracking operations without the detrimental effects of phase errors
Data Source
AI summary
A mainlobe detection process can include a number of tests that are performed to define when the monopulse antenna system will transition from open loop scanning to closed loop scanning and then to tracking. A hybrid tracking technique is also provided which adaptively discovers and corrects for phase alignment error. Magnitude-only tracking can be performed initially to locate the nulls in the azimuth and elevation ratios and to identify the magnitudes of these ratios at these nulls. Phase tracking can be then performed. During phase tracking, phase corrections can be repeatedly applied to the azimuth and elevation difference channels to correct any phase error that may exist. During this process, the magnitudes of the ratios can be used to determine how the phase corrections should be adjusted. Once the hybrid tracking process is complete, the monopulse antenna system is properly phase-aligned and phase tracking will be correctly employed.