Self-calibrating large baseline interferometer formed from two aircraft
a self-calibration, interferometer technology, applied in the direction of direction finders, instruments, measurement devices, etc., can solve the problems of limited accuracy of open loop approach and limited open loop method, and achieve the effect of rapid and accurate location
Active Publication Date: 2008-10-07
THE UNITED STATES OF AMERICA AS REPRESETNED BY THE SEC OF THE AIR FORCE
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Benefits of technology
The present invention provides a method to accurately locate a ground-based emitter using two aircraft to form a large baseline interferometer. The interferometer allows for various configurations for geo-location of ground-based emitters and cancels out two radio frequency signals through an iteratively adjusting variable delay line. The invention also provides a time based moving platform locating system providing angle and range information relative to a distant moving target through use of received radio frequency signals. The invention can be used for the location of a moving emitter, such as an airborne radar, using multiple interferometers each formed from two aircraft. The technical effects of the invention include rapid, accurate location of a stationary ground emitter, self-calibration notwithstanding the presence of environmental-sourced and other inaccuracy influences, and angle and range information relative to a distant moving target.
Problems solved by technology
The accuracy of this open loop approach is also limited by the sample times of a sampling clock and the linearity of the pulse leading edge.
The open loop method is also limited by the differences in the path lengths from the antenna to the measurement receiver.
Method used
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[0028]Traditionally interferometers operate by way of measuring signal phase characteristics. In large baseline interferometers, however, phase measurement provides ambiguous results because of the cyclic or periodic nature of the signal phase data. Time difference of arrival measurements are, however, not of this ambiguous nature since they are not cyclic or periodic in character. The time difference of arrival measurement arrangement is therefore the theoretical basis for the present invention as is disclosed in the paragraphs following.
[0029]Traditionally large baseline interferometers (LBI) are located on one aircraft. This limits the LBI length to the physical size of the aircraft. Examples are the side of the aircraft, the wing tips of the aircraft, or the nose to wing tip of the aircraft. U.S. Pat. No. 6,255,992 taught how to extend the LBI by using a tethered antenna and also taught how to calibrate the LBI to improve accuracy. (This calibration scheme can also be applied to...
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A method to passively locate an emitter using two aircraft to form a large baseline interferometer. The basic two element (two aircraft or helicopters) large baseline interferometer includes self-calibration and allows for various configurations for geo-location of ground-based emitters. The two aircraft large baseline interferometer can measure phase difference of arrival (PDOA) to very precisely locate the emitter in angle. Moving emitters can also be located and tracked using the method of the invention with greater accuracy than can be achieved from a single platform.
Description
RIGHTS OF THE GOVERNMENT[0001]The invention described herein may be manufactured and used by or for the Government of the United States for all governmental purposes without the payment of any royalty.CROSS-REFERENCE TO RELATED PATENTS[0002]The present document is somewhat related to my issued U.S. Patents “SELF-CALIBRATING LARGE BASELINE INTERFEROMETER FOR VERY PRECISE EMITTER LOCATION USING TIME DIFFERENCE OF ARRIVAL” and “TIME DIFFERENCE OF ARRIVAL RATE”, U.S. Pat. No. 6,255,992, issued Jul. 3, 2001; and “MOVING EMITTER PASSIVE LOCATION FROM MOVING PLATFORM”, U.S. Pat. No. 6,577,272, issued Jun. 10, 2003, and both commonly assigned to The United States of America as represented by the Secretary of the Air Force. The contents of these, my somewhat related issued patents, are hereby incorporated by reference.BACKGROUND OF THE INVENTION[0003]This invention relates to the field of remote energy-emitting source location through passive received signal processing.[0004]Although radio l...
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IPC IPC(8): G01S5/02
CPCG01S3/46G01S5/12G01S5/02216
Inventor MADDEN, THOMAS L.
Owner THE UNITED STATES OF AMERICA AS REPRESETNED BY THE SEC OF THE AIR FORCE