Monopulse Antenna Mainlobe Detection and Phase Alignment
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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 the high gain of sidelobes and poor signal-to-noise ratio performance, especially at large target ranges.
Innovation Solution
Implementing a mainlobe detection process that includes initial power-level tests during open loop scanning and track-lock tests during closed loop scanning to ensure the object is within the mainlobe, followed by magnitude-only tracking and phase tracking to correct phase alignment errors, using a monopulse detector assembly to generate ratios and steer the antenna accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the monopulse antenna system uses sidelobe signals for tracking, then the detection range is extended, but the signal-to-noise ratio performance deteriorates leading to link drops
Solution Approach 1:
The patent segments the detection process into distinct phases: open-loop scanning to identify potential targets in sidelobes, mainlobe verification to confirm legitimate targets, and closed-loop tracking for confirmed targets. This segmentation allows the system to extend detection range using sidelobes while maintaining reliability by verifying targets are in the mainlobe before engaging tracking.
Solution Approach 2:
The patent performs preliminary mainlobe verification through open-loop scanning and signal characteristic analysis before committing to closed-loop tracking. This preliminary action ensures that targets are genuinely in the mainlobe rather than sidelobes, preventing poor SNR performance while still allowing extended detection capability.
2Area of stationary object
If the antenna system tracks objects in sidelobes, then the field of view coverage is improved, but tracking stability deteriorates due to marginal signal-to-noise ratio
Solution Approach 1:
The patent introduces an intermediary verification process (open-loop scanning and mainlobe confirmation) between target detection and stable tracking. This intermediary step acts as a gatekeeper, ensuring only targets genuinely in the mainlobe proceed to closed-loop tracking, thereby maintaining tracking stability while preserving wide field of view coverage.
Solution Approach 2:
The patent employs feedback mechanisms where the system continuously monitors signal characteristics during open-loop scanning and uses this information to verify mainlobe presence before transitioning to closed-loop tracking. This feedback ensures tracking stability by preventing engagement with sidelobe targets, while still allowing comprehensive field of view monitoring.
3Loss of information
If the system uses modem lock signal as tracking indicator, then the tracking status can be monitored, but false positive tracking confirmation occurs when object is in sidelobe
Solution Approach 1:
The patent makes the tracking status indication dynamic by introducing a two-stage process: initial detection in open-loop mode with provisional tracking status, followed by mainlobe verification to confirm legitimate tracking. This dynamic approach allows the system to monitor tracking status accurately while avoiding false positives from sidelobe targets.
Solution Approach 2:
The patent performs preliminary mainlobe verification before confirming tracking status. By checking signal characteristics and verifying mainlobe presence through open-loop scanning before transitioning to closed-loop tracking, the system prevents false positive tracking confirmation while still providing effective tracking status monitoring.
4Measurement precision
If GPS and navigation data backbone is used for coarse tracking, then the initial pointing accuracy is improved, but the system complexity increases due to physical orientation requirements
Solution Approach 1:
The patent enables the monopulse antenna system to self-correct its pointing accuracy through automatic mainlobe verification and phase alignment procedures. By using the verification process to detect and correct pointing errors, the system achieves high initial pointing accuracy without requiring complex external GPS and navigation data backbones or tedious manual physical orientation.
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.