Method and apparatus for simultaneous multi-mode processing performing target detection and tracking using along track interferometry (ATI) and space-time adaptive processing (STAP)

#This invention relates to improved methods for target detection and tracking using radar data from platforms capable of performing simultaneous synthetic aperture radar (SAR), along-track interferometry (ATI) and beamforming.

#Remote sensing radar has been under development for the past several decades. It has provided a means for long-range continuous all-weather day/night observational capabilities that were not previously available. We now have the ability to perform long-distance ranging, observe large-scale weather patterns, construct digital elevation maps, measure significant changes in the earth's surface, map mineral distributions, detect moving targets and even construct images using measured radar echoes and sophisticated modern processing.

#Space Time Adaptive Processing (STAP) is a well-known method used to process spatio-temporal data to detect moving targets by employing a whitening operation followed by matched filtering in the spatio-temporal domian (J. Ward, Space-time adaptive processing for airborne radar. MIT Lincoln Laboratory, Technical Report 1015, December 1994; J. R. Guerci, Space-Time Adaptive Processing for Radar. Artech House; S. U. Pillai, K. Y. Li, and B. Himed, Space Based Radar: Theory & Applications. McGraw Hill Professional, December 2007.). SAR imaging was invented in the 1950s and has since been under continuous development. It is capable of imaging large swathes of terrain and all manners of objects visible to instruments operating in the RF spectrum. Moving target indication (MTI) such as air MTI (AMTI) and ground MTI (GMTI) are heavily used in both the military and civilian sectors for monitoring air and ground traffic. MTI radars are widely used for discrete surveillance and monitoring of sensitive areas. ATI is a well-known technique based on SAR images obtained from two phase centers separated by some distance in the along-track dimension (P. A. Rosen, Principles and Theory of Radar Interferometry, Tutorial for IGARSS, JPL Sep. 19, 2004). The advantage provided by ATI over SAR imaging alone is that by correlating the images from two different phase centers, the clutter scene (stationary background) is cancelled out and only moving targets are emphasized. ATI along with STAP has been used for estimating the velocities of both endoclutter and exoclutter targets. Slow-moving targets that are within the Doppler ridge generated by the platform are referred to as being in endoclutter while targets that are external to the Doppler ridge are referred to as being in exoclutter. ATI has an advantage over STAP when estimating the velocity of targets in endoclutter whereas STAP is more efficient at detecting targets in exoclutter.

#FIG. 1 shows a block diagram of an onboard apparatus and a ground station in accordance with an embodiment of the present invention, wherein the onboard apparatus may be located in a handheld device, which may communicate with the ground station;

#FIG. 2 illustrates measurement geometry for strip map-mode SAR/GMTI with a flight path of an aircraft vehicle to the left, and an observation scene with a target to the right;

#FIG. 3 illustrates a SAR/GMTI platform on an aircraft vehicle moving along a straight flight path, wherein the SAR/GMTI platform performs velocity estimation of a single moving target at two locations using STAP;

#FIG. 1 shows a block diagram of an apparatus 100 in accordance with an embodiment of the present invention and of a ground station 160 to which the apparatus 100 communicates. The apparatus 100 includes a computer memory 120, a computer processor 110, a transmitter/receiver 130, a computer interactive device 140, a computer display 150. The transmitter/receiver 130 may include a transmitter, a first receiver device, and a second receiver device, and any further number of receiver devices. Each receiver device of the transmitter/receiver 130 may be spaced apart from every other receiver device of the transmitter/receiver 130. The apparatus 100 may communicate with the ground station 160 through a data link in order to relay the data measured by the transmitter/receiver 130 or data processed by the on-board processor 110. The data link may be implemented by a transmitter/receiver such as 130 or by another transmitter/receiver of by some other mechanism such as a tactical data link system. The computer memory 120, the transmitter/receiver 130, the computer interactive device 140, the computer display 150 and the ground station 160 may communicate with and may be connected by communications links to the computer processor 110, such as by hardwired, wireless, optical, and/or any other communications links. The apparatus 100 may be part of or may be installed on any computer, such as a personal computer, a handheld portable computer device, such as a tablet computer, laptop computer, or portable smart phone.

#The transmitter/receiver 130 may be a radar or transmitter/receiver or a plurality of radio frequency transmitter/receivers.

#FIG. 2 illustrates a diagram 200. The diagram 200 shows an aircraft, airborne vehicle, or airplane 203, at a plurality of different locations to depict the flight of the airplane 203. The airplane 203 is shown at locations 203a, 203b, 203c, and 203d in FIG. 2, at four different instances of time as the airplane 203 flies along a path L1. The airplane 203 files through a space, area, time window or aperture, or subaperture 215 which may be a SAR/ATI/STAP subaperture.