Patent USH910H successfully refreshed from Google Patents.
USH910H
Expired / Lapsed
US
⏱️ 0.0 years remaining
Adaptive two dimensional shading for batch synthetic aperture radar using phased array antenna
Assignee: United States Department of the Air Force
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Filing: 1989-06-08
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Granted: 1991-04-02
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Expires: 2009-06-08
Abstract
Abstract A technique for correcting the non-uniform illumination and return echo strength from a mapped area resulting from antenna beam shape and range loss effects in a batch high resolution synthetic aperture radar. The technique involves changing the radar receiver gain in a precisely defined compensating manner and eliminates amplitude roll off at the edges of the display map so that equal target returns are displayed at equal amplitudes at any point of the map. The compensation arrangement requires minimal memory and computational overhead and thereby achieves minimal impact on frame time of the displayed map. The disclosure includes a computer simulation of the radar system performnce and comparison of the simulated before and after compensation radar maps.
Inventors
- 👤 Laurence J. Hindenach
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 17:04
CPC Classifications
G; G01; G01S; G01S13/00; G01S13/88; G01S13/89; G01S13/90; G01S13/904; G01S13/9047; G01S13/02; G01S2013/0236; G01S2013/0245
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
310 words
A method for amplitude equalizing the target return echo signals of a batch processed synthetic aperture pulsed doppler radar in accommodation of beam shape and target range perturbations of the return signal amplitudes over a target scene frame comprising the steps of: storing a target scene frame array of doppler frequency and range domain radar echo signal amplitudes data, said data being organized according to range cells dispersed across said target scene frame; selecting a predetermined number of points in the doppler frequency and range domain for performing antenna beam shape gain determinations; transforming the location of said gain determination points from the doppler frequency and range domain into points within the domain of an antenna face related coordinate system; performing antenna pattern gain determinations at each of said antenna coordinate domain points assuming a predetermined three dimensional beam shape; incorporating range attenuation effect correction into each of said antenna coordinate domain points gain determinations; determining the numeric coeffecients for a selected mathematically definable three dimensional gain surface extending in both the frequency and range directions, said gain surface being optimally conformed with said range attenuation effect correction inclusive antenna coordinate domain points; dividing said mathematically definable three dimensional gain surface into a predetermined number of range associated bands, each band including all of the frequency related gain surface values for a selected span of range values; ascertaining for the central most range values in each of said range bands, the numerical coefficients of a gain surface resident two-dimensional mathematical curve of gain versus frequency; computing from each of said two-dimensional mathematical curves the gain values at predetermined range cell locations disposed along each said curve; generating from said gain values a resolution cell dispersed array of inverse gain magnitude values; multiplying the amplitude values of said target frame range cell data by range cell respective inverse gain array values.
Claim 2
Independent Claim
310 words
A method for amplitude equalizing the target return echo signals of a batch processed synthetic aperture pulsed doppler radar in accommodation of beam shape and target range perturbations of the return signal amplitudes over a target scene frame comprising the steps of: storing a target scene frame array of doppler frequency and range domain radar echo signal amplitudes data, said data being organized according to range cells dispersed across said target scene frame; selecting a predetermined number of points in the doppler frequency and range domain for performing antenna beam shape gain determinations; transforming the location of said gain determination points from the doppler frequency and range domain into points within the domain of an antenna face related coordinate system; performing antenna pattern gain determinations at each of said antenna coordinate domain points assuming a predetermined three dimensional beam shape; incorporating range attenuation effect correction into each of said antenna coordinate domain points gain determinations; determining the numeric coeffecients for a selected mathematically definable three dimensional gain surface extending in both the frequency and range directions, said gain surface being optimally conformed with said range attenuation effect correction inclusive antenna coordinate domain points; dividing said mathematically definable three dimensional gain surface into a predetermined number of range associated bands, each band including all of the frequency related gain surface values for a selected span of range values; ascertaining for the central most range values in each of said range bands, the numerical coefficients of a gain surface resident two-dimensional mathematical curve of gain versus frequency; computing from each of said two-dimensional mathematical curves the gain values at predetermined range cell locations disposed along each said curve; generating from said gain values a resolution cell dispersed array of inverse gain magnitude values; multiplying the amplitude values of said target frame range cell data by range cell respective inverse gain array values.
Claim 3
Dependent Claim
22 words
The method of claim 1 wherein said points in the domain of doppler frequency and doppler range are divided into N groups.
Claim 4
Dependent Claim
12 words
The method of claim 2 wherein N has a value of three.
Claim 5
Dependent Claim
18 words
The method of claim 1 wherein said antenna face related coordinate system is the direction cosine space domain.
Claim 6
Dependent Claim
13 words
The method of claim 1 wherein said beam shape is Gaussian in nature.
Claim 7
Dependent Claim
20 words
The method of claim 1 wherein said selected three-dimensional gain surface is parabolic in both the frequency and range directions.
Claim 8
Dependent Claim
19 words
The method of claim 6 wherein said optimally conformed gain surface is fitted by a least squares fitting method.
Claim 9
Dependent Claim
14 words
The method of claim 1 wherein said range associated bands are sixteen in number.
Claim 10
Dependent Claim
19 words
The method of claim 1 wherein said ascertaining step numerical coefficients computations are performed by a discrete double integrator.
Claim 11
Dependent Claim
31 words
The method of claim 1 wherein said discrete double integrator is operated from the center of said target scene once in each direction and generates symmetric errors at the scene edges.
Claim 12
Dependent Claim
21 words
The method of claim 1 wherein said inverse gain magnitude values are generated from a look up table array of values.
Claim 13
Dependent Claim
37 words
The method of claim 1 wherein said step of performing antenna pattern gain determinations includes mathematically estimating the gain for a sample point from the 3-decibel signal locus and the known geometric relationships in the radar beamshape.
Claim 14
Dependent Claim
25 words
The method of claim 1 wherein said target scene frame is resolved into a resolution cell grid of at least four hundred cells per side.
Claim 15
Dependent Claim
37 words
The method of claim 1 wherein said antenna pattern gain determination performance step includes selecting a sample set of cells and mathematically estimating the gain for each said sample cell using sample cell subset least squares fitting.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-04-01 | 1994-10-01 | 1995-04-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-04-01 | 1998-10-01 | 1999-04-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-04-01 | 2002-10-01 | 2003-04-02 | $7700.00 | Window Closed / Lapsed |