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ECCM (Electronic Counter-Countermeasure) Effectiveness of a Low Sidelobe Antenna for SAR (Synthetic Aperture Radar) Ground Mapping.

N8718730

Publication Date	1986
Personal Author	Boesswetter, C.
Page Count	1
Abstract	Airborne synthetic aperture radar (SAR) reconnaissance systems in the strip mapping mode are susceptible to jamming. The main electronic counter measure (ECM) threat is commonly understood to be the ground based sidelobe jammer which includes a sensitive intercept receiver and a tracking capability to adapt the jamming power in angle, frequency and bandwidth to the SAR system. The most important of several necessary electronic counter-countermeasure (ECCM) techniques is commonly considered to be a low sidelobe SAR antenna which also improves MTI performance. To characterize the ECCM and cost effectiveness of such an expensive antenna some measures are needed. There are two separate phases: intercept and jamming. Accordingly, two gains are defined: intercept gain and jamming gain. Both are based on the evaluation of the signal-to- (jammer plus clutter plus noise) ratio in the processed SAR image for the configuration airborne sensor-ground based jammer. Both gains descibe the benefits of a low side lobe antenna in terms of jam-free flight distance (intercept) and target contrast enhancement (jamming). It is shown that in the most interesting case of heavy jamming both intercept and jamming phases are discribed by the same set of equations if normalized to the pointing direction R sub 0 of the antenna. It follows that the intercept ratio on the ground equals the reciprocal of the target contrast in the processed SAR image. To discuss both the intercept and jamming gain performance of a given SAR antenna 3-dimensional relief plots and 2-dimensional contour plots are used. They allow the definition of both gains directly. For the parameters of a given SAR reconnaissance system the plots are calculated in an area of 120 nmi x 180 nmi (azimuth x range). By replacing the existing antenna with uniform weighting with an antenna with 25 dB lower sidelobe level the ECCM effectiveness in terms of intercept gain and jamming gain is shown. Since the equations are normalized to the pointing direction of the sensor antenna the results are given in relative terms. By including actual jammer parameters the ECCM effectiveness may also be given in absolute terms.
Keywords	Radar antennas Radar maps Sidelobes Aerial reconnaissance Airborne surveillance radar Electronic countermeasures Imaging radar Mapping Synthetic aperture radar Clutter Jamming Signal to noise ratios Foreign technology
Source Agency	NASA Foreign Exchange Program
NTIS Subject Category	63H - Radiofrequency Detection 49A - Antennas 63B - Electromagnetic & Acoustic Countermeasures
Corporate Authors	Deutsche Forschungs- und Versuchsanstalt fuer Luft- und Raumfahrt e.V., Oberpfaffenhofen (Germany, F.R.).; National Aeronautics and Space Administration, Washington, DC.
Supplemental Notes	In AGARD Multifunction Radio for Airborne Applications 1 p.
Document Type	Analytic Daughter
Title Note	Abstract Only.
NTIS Issue Number	198713

ECCM (Electronic Counter-Countermeasure) Effectiveness of a Low Sidelobe Antenna for SAR (Synthetic Aperture Radar) Ground Mapping.

ECCM (Electronic Counter-Countermeasure) Effectiveness of a Low Sidelobe Antenna for SAR (Synthetic Aperture Radar) Ground Mapping.
N8718730

Publication Date	1986
Personal Author	Boesswetter, C.
Page Count	1
Abstract	Airborne synthetic aperture radar (SAR) reconnaissance systems in the strip mapping mode are susceptible to jamming. The main electronic counter measure (ECM) threat is commonly understood to be the ground based sidelobe jammer which includes a sensitive intercept receiver and a tracking capability to adapt the jamming power in angle, frequency and bandwidth to the SAR system. The most important of several necessary electronic counter-countermeasure (ECCM) techniques is commonly considered to be a low sidelobe SAR antenna which also improves MTI performance. To characterize the ECCM and cost effectiveness of such an expensive antenna some measures are needed. There are two separate phases: intercept and jamming. Accordingly, two gains are defined: intercept gain and jamming gain. Both are based on the evaluation of the signal-to- (jammer plus clutter plus noise) ratio in the processed SAR image for the configuration airborne sensor-ground based jammer. Both gains descibe the benefits of a low side lobe antenna in terms of jam-free flight distance (intercept) and target contrast enhancement (jamming). It is shown that in the most interesting case of heavy jamming both intercept and jamming phases are discribed by the same set of equations if normalized to the pointing direction R sub 0 of the antenna. It follows that the intercept ratio on the ground equals the reciprocal of the target contrast in the processed SAR image. To discuss both the intercept and jamming gain performance of a given SAR antenna 3-dimensional relief plots and 2-dimensional contour plots are used. They allow the definition of both gains directly. For the parameters of a given SAR reconnaissance system the plots are calculated in an area of 120 nmi x 180 nmi (azimuth x range). By replacing the existing antenna with uniform weighting with an antenna with 25 dB lower sidelobe level the ECCM effectiveness in terms of intercept gain and jamming gain is shown. Since the equations are normalized to the pointing direction of the sensor antenna the results are given in relative terms. By including actual jammer parameters the ECCM effectiveness may also be given in absolute terms.
Keywords	Radar antennas Radar maps Sidelobes Aerial reconnaissance Airborne surveillance radar Electronic countermeasures Imaging radar Mapping Synthetic aperture radar Clutter Jamming Signal to noise ratios Foreign technology
Source Agency	NASA Foreign Exchange Program
NTIS Subject Category	63H - Radiofrequency Detection 49A - Antennas 63B - Electromagnetic & Acoustic Countermeasures
Corporate Authors	Deutsche Forschungs- und Versuchsanstalt fuer Luft- und Raumfahrt e.V., Oberpfaffenhofen (Germany, F.R.).; National Aeronautics and Space Administration, Washington, DC.
Supplemental Notes	In AGARD Multifunction Radio for Airborne Applications 1 p.
Document Type	Analytic Daughter
Title Note	Abstract Only.
NTIS Issue Number	198713