Communications: directive radio wave systems and devices (e.g. – Directive – Beacon or receiver
Reexamination Certificate
2000-04-13
2001-07-03
Hellner, Mark (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Beacon or receiver
C342S442000
Reexamination Certificate
active
06255992
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the field of remote energy-emitting source location through passive received signal processing.
Although radio locating has been used since the early days of radio, current military apparatus with its limited output signal durations and the availability of computerized signal processing, faster analog to digital conversion apparatus and a need to accomplish rapid accurate signal locations from a moving vehicle provide opportunity for improvement in this art.
Present aircraft based radio frequency emitter locating methods for example require use of two platforms to obtain angle and range data relating to a radio frequency emitting energy source or one platform flying for some seconds to obtain a multiple line of bearings (i.e., multiple angles of arrivals). In both of these cases range is determined by an intersection on multiple line of bearings. In this invention precisely measured time difference of arrival and a single aircraft are used to determine line of bearing to an emitter and time difference of arrival rate at this aircraft is used to determine emitter range.
SUMMARY OF THE INVENTION
The present invention provides unambiguous locating of a distant source of radio frequency energy from a moving platform, such as an aircraft. The identified location may be relative to the search aircraft or may be a geolocation determined with respect to the earth. The distant emission source may be of a pulsed output nature, such as a radar apparatus, and the achieved location may be accomplished with as little as two successive emission pulses.
It is an object of the present invention, therefore, to provide rapid accurate location of a stationary ground emitter, such as a radar transmitter, from a moving platform.
It is another object of the invention to provide distant radar location in azimuth, elevation and range through concurrent use of two nominally orthogonal large baseline interferometers.
It is another object of the invention to provide a time based unambiguous locating system for a distant radio frequency energy source.
It is another object of the invention to provide location of a radar emission which may be random pulse to pulse frequency agile.
It is another object of the invention to provide a time based distant radio frequency source locating arrangement in which a calibration sub system maintains usable accuracy notwithstanding presence of environmental-sourced and other inaccuracy influences.
It is another object of the invention to provide a time based distant radio frequency source locating arrangement employing a recalibration-correctable locating algorithm.
It is another object of the invention to provide a distant radio frequency source locating arrangement embodied in a moving platform, such as an aircraft, and employing platform-peripheral signal collection.
It is another object of the invention to provide a distant radio frequency source locating arrangement capable of enhanced location accuracy through use of an input antenna separation-enhancing trailing antenna member.
It is another object of the invention to provide a distant radio frequency source locating arrangement supported by a propagation time-based mathematical algorithm.
It is another object of the invention to provide a distant radio frequency source locating arrangement supported by a propagation time delay-based array of mathematical equations.
It is another object of the invention to provide a time difference of arrival emission source locating arrangement disposable in either of the azimuth or elevation planes, a locating arrangement usable in replication to determine both azimuth and elevation locations of a distant radio frequency source.
It is another object of the invention to provide both relative and absolute or geo location of a remote radio frequency emission source.
It is another object of the invention to provide rapid location of a remote radio frequency emission source, that is location within the time of a second or less.
It is another object of the invention to provide a long baseline interferometer and moving platform digital apparatus for distant emission source location.
It is another object of the invention to provide an airborne distant emission source location arrangement in which known aircraft velocity and long baseline interferometer-determined angle of arrival information are used to determine emitter location.
Additional objects and features of the invention will be understood from the following description and claims and the accompanying drawings.
These and other objects of the invention are achieved by an airborne long baseline interferometer radio frequency signal emitter source locating apparatus comprising the combination of:
a signal emitter search aircraft containing first and second radio frequency receivers and input and output signal conveying members connected therewith;
said first and second radio frequency receivers being disposed in receipt of signals from said radio frequency signal emitter source by way of first and second antenna members disposed in physically separated portions of said aircraft and said signal conveying members;
time difference of arrival signal processing apparatus received in said aircraft in communication with output signals of said first and second radio frequency receivers, said apparatus being responsive to ranges of arrival time difference and arrival time difference rate occurring in signals from said radio frequency signal emitter source output by said first and second radio frequency receivers;
selectively operable signal propagation time delay calibration apparatus electively connectable with said signal conveying members in paths interconnecting said first and second antennas with said time difference of arrival signal processing apparatus and generating picosecond-resolved measurement data representing environment-induced changes in signal propagation delay attending signal propagation in said signal conveying members.
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Hellner Mark
Hollins Gerald B.
Kundert Thomas L.
The United States of America as represented by the Secretary of
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