Sensor Buoy RF Range Limiting for LPI Signal Detection
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Solution Overview
Problem
Existing maritime domain awareness systems struggle to detect low power or difficult-to-detect transmissions from vessels, such as class-B AIS signals and VHF transmitters, due to limited range and interference, especially in areas not covered by satellite collectors.
Innovation Solution
A sensor buoy equipped with an electrically small antenna, IFM receiver, PDW generator, processor, magnetometer, and transmitter, configured to float on water and limit RF range to 15 kilometers, enabling detection and geolocation of low probability of intercept (LPI) emitters and other hard-to-detect signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a large antenna is used to detect signals from distant vessels, then the detection range is extended, but the ability to resolve and accurately detect low power signals from specific emitters is degraded due to interference from other emitters
Solution Approach 1:
The patent applies local quality by using an electrically small antenna with a deliberately limited RF range of view (no more than fifteen kilometers). This localized reception capability allows the buoy to focus on detecting low power signals from specific emitters within its limited range without being overwhelmed by interference from distant emitters, thereby improving signal resolution accuracy while maintaining extended detection capability through multiple buoys in the maritime domain.
2Object-affected harmful factors
If the RF range of view is limited to fifteen kilometers, then interference from distant emitters is reduced, but the overall coverage area is decreased
Solution Approach 1:
The patent applies segmentation by deploying multiple sensor buoys throughout the maritime domain, each with a limited RF range of view of no more than fifteen kilometers. This segmented approach allows each buoy to independently detect low power signals within its local area without interference, while the collective network of buoys provides comprehensive coverage of the entire maritime domain, effectively resolving the contradiction between reduced interference and maintained coverage.
3Measurement precision
If an electrically small antenna is used to limit RF range, then low power signal detection is improved, but the antenna gain and sensitivity are reduced
Solution Approach 1:
The patent applies the intermediary principle by using the electrically small antenna as a mediator that deliberately limits the RF range of view to no more than fifteen kilometers. This limited-range antenna acts as an intermediary that filters out distant emitters and focuses reception on nearby low power signals, enabling accurate detection of LPI emitters while the buoy's processing systems compensate for reduced antenna gain through signal processing techniques.
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
The sensor buoy provides accurate, low-power detection and geolocation of LPI emitters within a limited area, reducing interference and enhancing maritime domain awareness by transmitting data via satellite when conditions are optimal, thus improving detection capabilities in challenging environments.
Implementation Method 1
mounting an electrically small antenna to the buoy casing in a position so as to provide a limited RF reception range of no more than fifteen kilometers. Another step provides for receiving RF signals from an emitter with the antenna.
Implementation Method 2
a buoy casing configured to float on a body of water
Implementation Method 3
The magnetometer is communicatively coupled to the processor
Data Source
AI summary
A sensor buoy comprising: a buoy casing configured to float on a body of water; an antenna mounted to the buoy casing so as to limit an RF range of view to no more than fifteen kilometers; an instantaneous frequency measurement (IFM) receiver mounted to the buoy casing and communicatively coupled to the antenna; a pulse descriptor word (PDW) generator mounted to the buoy casing and configured to receive an output from the IFM receiver; a processor configured to receive PDWs generated by the PDW generator and to calculate a corresponding pulse repetition interval (PRI); a magnetometer communicatively coupled to the processor; a scheduler communicatively coupled to the processor and configured to control when the sensor buoy transmits information; and a transmitter communicatively coupled to the scheduler and configured to format data from the processor into a correct format and packet structure for transmission.