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US-12627329-B2 - Low probability of intercept signal interceptor buoy

US12627329B2US 12627329 B2US12627329 B2US 12627329B2US-12627329-B2

Abstract

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.

Inventors

  • Gregory Knowles Fleizach
  • Barry R. Hunt
  • Doug Kenneth Herbers

Assignees

  • THE UNITED STATES OF AMERICA, AS REPRESENTED BY THE SECRETARY OF THE NAVY

Dates

Publication Date
20260512
Application Date
20240227

Claims (20)

  1. 1 . A sensor buoy comprising: a buoy casing configured to float on a body of water; an antenna that is electrically small and 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.
  2. 2 . The sensor buoy of claim 1 , wherein the antenna comprises N receive antennas with approximately 360°/N horizontal beamwidths positioned to function as sector antennas.
  3. 3 . The sensor buoy of claim 2 , wherein the buoy casing is an untethered drifting buoy.
  4. 4 . The sensor buoy of claim 2 , wherein the buoy casing is a station-keeping buoy.
  5. 5 . The sensor buoy of claim 2 , wherein the receive antennas are mounted on the buoy casing above a surface of the body of water but no greater than 0.25 meters above the surface so as to limit the senor buoy's radar horizon, with respect to a distant emitter ten meters above the surface, to no more than fifteen kilometers.
  6. 6 . The sensor buoy of claim 5 , wherein the transmitter is capable of transmitting packets to an Earth satellite.
  7. 7 . The sensor buoy of claim 6 , wherein the processor is further configured to calculate the PRI based on a measured time between time of arrivals for adjacent pulses at a same frequency.
  8. 8 . A method for increasing maritime domain awareness comprising: providing a buoy casing configured to float on a body of water, wherein the buoy casing is equipped with a global positioning system (GPS) tracker and a magnetometer, both of which being communicatively coupled to a processor which is mounted to the buoy casing; 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, wherein the antenna is horizontally polarized; receiving RF signals from an emitter with the antenna; determining characteristics of the RF signals with the processor, wherein the determining characteristics of the RF signals further comprises: measuring a frequency of each of the RF signals with an instantaneous frequency measurement (IFM) receiver; feeding an output of the IFM receiver to a pulse descriptor word (PDW) generator to generate PDWs corresponding to the RF signals; establishing a rough geolocation the size of the limited reception range of the emitter based on detection of the RF signal alone; and transmitting the RF signal characteristics and the corresponding rough geolocation of the emitter via satellite to a remote user.
  9. 9 . The method of claim 8 , wherein the step of determining characteristics of the RF signals further comprises: measuring a time between time of arrivals (TOAs) for adjacent RF signal pulses having the same frequency.
  10. 10 . The method of claim 9 , wherein the antenna comprises N receive antennas having 360°/N horizontal beamwidths.
  11. 11 . The method of claim 10 , further comprising establishing with the processor a better geolocation of the emitter based on an angle-of-arrival (AOA) of the RF signals and a radar horizon of the N receive antennas.
  12. 12 . The method of claim 11 , wherein the step of determining characteristics of the RF signals further comprises determining a scan rate from azimuth-rotating radars on the emitter by monitoring fluctuating RF signal power levels received by the N receive antennas.
  13. 13 . The method of claim 12 , further comprising using a scheduler communicatively coupled to the processor to control when the transmitting step is performed such that transmissions are sent according to a schedule.
  14. 14 . The method of claim 13 , wherein the schedule limits transmissions to once a day.
  15. 15 . The method of claim 8 , wherein the antenna is a whip antenna capable of receiving very high frequency (VHF) signals, and further comprising performing the transmitting step immediately upon receiving a channel sixteen VHF signal.
  16. 16 . The method of claim 8 , wherein the RF signal is a class-B automatic identification system (AIS) signal.
  17. 17 . The method of claim 8 , wherein the buoy casing is configured to be a station-keeping buoy and is positioned in an ocean at an edge of a sensitive area.
  18. 18 . The method of claim 8 , wherein the antenna is mounted to the buoy casing at approximately 0.25 meters above a surface of the body of water.
  19. 19 . The method of claim 8 , wherein the RF signal is a Wi-Fi signal from another vessel.
  20. 20 . The method of claim 8 , wherein the antenna comprises a whip antenna and N receive antennas having 360°/N horizontal beamwidths.

Description

FEDERALLY-SPONSORED RESEARCH AND DEVELOPMENT The United States Government has ownership rights in the invention claimed herein. Licensing and technical inquiries may be directed to the Office of Research and Technical Applications, Naval Information Warfare Center Pacific, Code 72110, San Diego, CA, 92152; voice (619) 553-5118; NIWC_Pacific_T2@us.navy.mil. Reference Navy Case Number 210997. BACKGROUND OF THE INVENTION Maritime domain awareness (MDA) is the effective understanding of anything associated with the maritime domain that could impact the security, safety, economy, or environment. Transmissions from a given vessel, such as automatic identification system (AIS) signals, may be used to identify the given vessel's location, among other data to improve MDA. However, some transmissions are low power or otherwise difficult to detect. There is a need for a way to improve MDA. SUMMARY Disclosed herein is a sensor buoy comprising a buoy casing, an antenna, an instantaneous frequency measurement (IFM) receiver, a pulse descriptor word (PDW) generator, a processor, a magnetometer, a scheduler, and a transmitter. The buoy casing is configured to float on a body of water. The antenna is electrically small and mounted to the buoy casing so as to limit a radio frequency (RF) range of view to no more than fifteen kilometers. The IFM receiver is mounted to the buoy casing and communicatively coupled to the antenna. The PDW generator is mounted to the buoy casing and configured to receive an output from the IFM receiver. The processor is configured to receive PDWs generated by the PDW generator and to calculate a corresponding pulse repetition interval (PRI). The magnetometer is communicatively coupled to the processor. The scheduler is communicatively coupled to the processor and configured to control when the sensor buoy transmits information. The transmitter is communicatively coupled to the scheduler and configured to format data from the processor into a correct format and packet structure for transmission. Also disclosed herein is a method for increasing maritime domain awareness comprising the following steps. The first step involves providing a buoy casing configured to float on a body of water. The buoy casing is equipped with a global positioning system (GPS) tracker and a magnetometer, both of which are communicatively coupled to a processor which is mounted to the buoy casing. Another step provides for 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. Another step provides for determining characteristics of the RF signals with the processor. Another step provides for establishing a rough geolocation the size of the limited reception range of the emitter based on detection of the RF signal alone. Another step provides for transmitting the RF signal characteristics and the corresponding rough geolocation of the emitter via satellite to a remote user. BRIEF DESCRIPTION OF THE DRAWINGS Throughout the several views, like elements are referenced using like references. The elements in the figures are not drawn to scale and some dimensions are exaggerated for clarity. FIG. 1A is a perspective-view illustration of an embodiment of a sensor buoy. FIG. 1B is a side-view illustration of a sensor buoy and a vessel on a water surface. FIG. 2 is a block diagram of an embodiment of a sensor buoy. FIG. 3 is a side-view illustration of an embodiment of a sensor buoy. FIG. 4 is a flowchart. FIG. 5 is a perspective-view illustration of an embodiment of a sensor buoy. DETAILED DESCRIPTION OF EMBODIMENTS The disclosed buoy and methods below may be described generally, as well as in terms of specific examples and/or specific embodiments. For instances where references are made to detailed examples and/or embodiments, it should be appreciated that any of the underlying principles described are not to be limited to a single embodiment, but may be expanded for use with any of the other methods and systems described herein as will be understood by one of ordinary skill in the art unless otherwise stated specifically. FIG. 1A is a perspective-view illustration of an embodiment of a sensor buoy 10 that comprises, consists of, or consists essentially of a buoy casing 12, an electrically small antenna 14, an IFM receiver 16, a PDW generator 18, a processor 20, a magnetometer 22, a scheduler 24, and a transmitter 26. The buoy casing 12 is configured to float on a surface 28 of a body of water. FIG. 1B is a side-view illustration of the sensor buoy 10 on the water surface 28. In this embodiment of the sensor buoy 10, the antenna 14 comprises four receive antennas that have approximately 90° horizontal beamwidths and are mounted to the buoy casing 12 so as to provide a limited RF range of view of no more than fifteen kilometers. The antenna 14 may be hori