Communications: directive radio wave systems and devices (e.g. – Synthetic aperture radar
Reexamination Certificate
1998-12-09
2001-03-20
Gregory, Bernarr E. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Synthetic aperture radar
C342S02600R, C342S104000, C342S106000, C342S190000, C342S191000, C342S192000, C342S195000, C342S196000
Reexamination Certificate
active
06204800
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention is directed to a method for monitoring the earth's surface using synthetic aparture radar.
Monitoring of the surface of the earth is required for many applications. A moving aircraft, e.g. an airplane or a dirigible or a satellite, may be used, if the monitoring for the most part must be independent of the influence of weather conditions, e.g. clouds and/or fog, it makes sense to provide an aircraft with a radar sensor having a viewing direction toward the earth's surface. In the event that high spatial resolution must be achieved during the monitoring, it makes sense to use a radar sensor with a synthetic aperture. This radar sensor is operated, for example, in the so-called SAR mode or the DBS mode (operating mode). This type of radar monitoring requires that the flight parameters in particular are always known, e.g. flight elevation, flight path, and flight speed of the aircraft. Only if these are known can radar images, recorded successively in time with the synthetic aperture method, be evaluated with predetermined accuracy, without the occurrence of errors and/or interferences such as fuzzy images. The aforementioned flight parameters can be determined, for example, with an INS (inertial navigation system).
Such a method has the disadvantage of being technically involved and not cost-effective because an autonomous device, the INS device, must be used to determine the parameters, required in particular for SAR radar images.
SUMMARY OF THE INVENTION
It is thus the object of the invention to specify a method of the type discussed above, which permits in a cost-effective manner an automatic focusing of radar images, generated with the aid of a radar sensor with a synthetic aperture.
This object is solved with a monitoring system which is characterized in that the transmitting/receiving antenna of the radar sensor is designed such that in the region to be monitored, an illuminated spot for the antenna is generated, which is adapted to a specifiable spatial resolution; a radar image is generated from the received radar signals through superimposing Fourier spectra, which have been processed block-by-block with respect to the range and/or the Doppler signal. By correlating such Fourier spectra, which succeed each other in time, in the azimuth and elevation dimensions, it is possible to determine the parameters acceleration on the line of sight (B
los
), as well as ambiguity errors on the line of sight (M
los
). The remaining speed on the line of sight (R
los
) is determined within an ambiguity range by estimating the echo center of gravity of the Doppler signal within the Fourier spectra. A definite speed is determined on the line of sight (V
los
) in accordance with the following formula:
(
V
los
)=(
M
los
)·&lgr;
B
m
/2
+R
los
,
wherein
·=multiplication operator
&lgr;=radar wave length; and
B
m
=measuring band width of the radar sensor in Doppler.
The parameters phase correction range (
&phgr;
r
) and phase correction Doppler (
&phgr;
d
), which are necessary to focus the radar images, are determined from the acceleration on the line of sight (B
los
) and the speed on the line of sight (V
los
).
BRIEF DESCRIPTION OF THE DRAWINGS
REFERENCES:
patent: 4924229 (1990-05-01), Eichel et al.
patent: 5172118 (1992-12-01), Peregrim et al.
patent: 5172119 (1992-12-01), Young et al.
patent: 5172120 (1992-12-01), Slawsby et al.
patent: 5173703 (1992-12-01), Mangiapane et al.
patent: 5185608 (1993-02-01), Pozgay
patent: 5969662 (1999-10-01), Hellsten
patent: 4311754C1 (1994-06-01), None
patent: 4427657A1 (1996-02-01), None
patent: 0449303A2 (1991-10-01), None
Daimler-Benz Aerospace AG
Gregory Bernarr E.
Spencer George H.
Venable
Wood Allen
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