US 6,700,527 B1 · Coherent two-dimensional image formation by passive synthetic aperture collection and processing of multi-frequency radio signals scattered by cultural features of terrestrial region

Abstract

An imaging system uses wideband ‘RF daylight’ created by plural narrowband RF illumination sources, to passively generate spectrally different sets of RF scattering coefficients for multiple points within a prescribed three-dimensional volume being illuminated by the narrowband RF transmitters. To correct for the lack of mutual coherence among different RF illumination sources, the respective sets of scattering coefficient data are applied to a cultural feature extraction operator, to locate one or more strong cultural features spatially common to multiple images. For spatial points along the extracted cultural feature theoretical scattering coefficients are calculated. Differences between phase values of these calculated scattering coefficients and those of the collected and processed scattering energy are used to modify the measured scattering coefficient values for all spatial points in the illuminated region. This allows the scattering coefficients of that narrowband frequency set to be coherently combined with those of another spectrally different narrowband set of scattering coefficients whose phase components have been similarly corrected, based upon the same extracted cultural feature.

Claims24

Dependent claims

A method of generating an image of a terrestrial region upon which electromagnetic energy from respectively different narrowband energy sources is incident comprising the steps of:

(a) passively collecting electromagnetic energy emitted by said respectively different narrowband energy sources by way of at least one first energy collector;
(b) passively collecting, by at least one second energy collector moving independently and arbitrarily with respect to said respectively different narrowband energy sources among a plurality of distributed energy collection locations, electromagnetic energy emitted by said electromagnetic energy sources and scattered by features of said terrestrial region of interest;
(c) processing a reference signal representative of electromagnetic energy collected in step (a), in accordance with information representative of the collection geometry of said at least one first energy collector and the geolocations of said electromagnetic energy sources, so as to derive a time- and location-corrected reference signal;
(d) correlating the time- and location-corrected reference signal derived in step (c) with image signals representative of electromagnetic energy collected by said at least one moving second energy collector in step (b), so as to derive amplitude and phase values of scattering components for each of said narrowband sources for plural locations of said terrestrial region as received by said at least one moving second energy collector as a function of spatial position;
and
(e) processing scattering components derived in step (d) for each of said respectively different narrowband sources to produce said multidimensional image of said terrestrial region of interest.

3 more elements

A system for deriving image information representative of cultural features of a terrestrial region illuminated by spectrally different RF transmitters comprising:

a reference signal collection subsystem which is operative to collect non-scattered RF energy emitted by said spectrally different RF transmitters illuminating said terrestrial region;
a dynamic scattered image energy subsystem which is operative to travel past said terrestrial region, moving arbitrarily and independently with respect to said spectrally different RF transmitters and collect RF energy scattered from points of cultural features within said terrestrial region;
and
a collected signal processing subsystem, which is operative to process information representative of said non-scattered RF energy as collected by said reference signal collection subsystem, to derive coherent reference signals corresponding to those transmitted by said RF transmitter illuminating said terrestrial region, time- and location-corrected as necessary to points within said terrestrial region, and to correlate said coherent reference signals with a scattered RF energy signals representative of electromagnetic energy collected by said dynamic scattered image energy subsystem, time- and location-corrected as necessary to said points within said terrestrial region, so as to derive respective sets of amplitude and phase values of scattering components for said points of said terrestrial region, and is operative to process respective sets of scattering components derived for each of said respectively different narrowband sources to coherently combinable sets of scattering coefficients.

1 more element

A method for passively deriving image information representative of cultural features of a region illuminated by a plurality of spectrally different narrowband RF transmitters comprising the steps of:

(a) providing coherent reference signals representative of RF energy emitted by said spectrally different RF transmitters illuminating said terrestrial region;
(b) collecting, from at least one energy collector moving arbitrarily and independently of said plurality of spatially different narrowband RF transmitters along a prescribed portion of a travel path offset from said terrestrial region, RF energy scattered, as a result of illumination by RF energy emitted by said spectrally different RF transmitters, from points that are capable of defining cultural features within said terrestrial region;
(c) correlating said coherent reference signal, time- and location-corrected as necessary to said points of said terrestrial region, with scattered RF energy signals associated with said spectrally different transmitters and representative of electromagnetic energy collected by said dynamic scattered image energy subsystem, time- and location-corrected as necessary to said points of said terrestrial region, so as to derive respective sets of scattering components for said spectrally different narrowband sources for said points of said terrestrial region;
and
(d) performing phase coherence processing of said scattering, components for each of said spectrally different narrowband RF sources so as to produce a composite set of scattering components for said terrestrial region from which a multidimensional image may be generated.

2 more elements

A method of generating an image of a terrestrial region comprising the steps of:

(a) passively collecting non-scattered electromagnetic energy, emitted by respectively different narrowband electromagnetic energy transmitters illuminating said terrestrial region, at a first, passive, electromagnetic energy collector that is exclusive of any electromagnetic energy transmission element employed by said respectively different narrowband electromagnetic energy transmitters to transmit narrowband electromagnetic energy;
(b) passively collecting, by a second passive electromagnetic energy collector, electromagnetic energy emitted by said narrowband electromagnetic energy transmitters and scattered by features of said terrestrial region of interest, said second passive electromagnetic energy collector moving independently and arbitrarily with respect to said respectively different narrowband electromagnetic energy transmitters illuminating said terrestrial region among a plurality of distributed energy collection locations and being exclusive of any electromagnetic energy transmission element employed by any of said respectively different narrowband electromagnetic energy transmitters;
(c) processing a reference signal representative of electromagnetic energy collected in step (a), in accordance with information representative of the collection geometry of said first energy collection element and geolocations of said electromagnetic energy transmitters, so as to derive a time- and location-corrected reference signal;
(d) correlating said time- and location-corrected reference signal derived in step (c) with image signals representative of electromagnetic energy collected by said moving second energy collector in step (b), so as to derive amplitude and phase values of scattering components for each of said narrowband electromagnetic energy transmitters for plural locations of said terrestrial region as received by said moving second energy collector as a function of spatial position;
and
(e) processing scattering components derived in step (d) for each of said respectively different narrowband electromagnetic energy transmitters to produce said multidimensional image of said terrestrial region of interest.

3 more elements

Dependencies are inferred from the claim text.

Coherent two-dimensional image formation by passive synthetic aperture collection and processing of multi-frequency radio signals scattered by cultural features of terrestrial region

Life of this patent

Coherent two-dimensional image formation by passive synthetic aperture collection and processing of multi-frequency radio signals scattered by cultural features of terrestrial region

Life of this patent

Abstract

Claims24