VHF/UHF Radar Signatures of Foliage-Obscured Threat Military Vehicles A. J. Gatesman, M. Testorf, C. Beaudoin, M. Fiddy, R. Giles, J. Waldman Submillimeter-Wave Technology Laboratory University of Massachusetts Lowell K. Ding, J. Poirier Air Force Research Laboratory Hanscom Air Force Base, MA 01730 W. Nixon U.S. Army National Ground Intelligence Center Charlottesville, VA 22902 STL website: http://stl.uml.edu/stlweb/index.html 1
Physical Scale Modeling Radar Measurements 35 feet 35 feet 1 foot 1 foot 200 MHz - 400 MHz 200 MHz - 400 MHz 7 GHz - 14 GHz 7 GHz - 14 GHz Radar wavelength: 1 m Scaled radar wavelength: 1 inch (X-band) Advantages of Scale Modeling Radar Measurements: : Advantages of Scale Modeling Radar Measurements - Rapidly generate calibrated signature libraries - Rapidly generate calibrated signature libraries - Controlled, covert environment - Controlled, covert environment - Models built from intelligence data - Models built from intelligence data - Rough ground planes, clutter, trees - Rough ground planes, clutter, trees 2
Microwave Radar Range scaled target & scene computer control/ microwave antenna system transceiver anechoic chamber lo target support translation/ rotation hardware • Based on HP vector network analyzer • 8.2 - 12.4 GHz models 234 - 354 MHz at 1/35 th scale • Automated calibration and target positioning hardware 3
1/35 th Scale Vehicles, Terrain, Trees 4
Signature Validation with 1/16 th Scale Slicy 5
VHF TRCS of Slicy Compared with CARLOS at 285.7 MHz and 15° elevation VV data HH data 30 30.00 HH data VV carlos HH Carlos VV data (wide gate) 20 20.00 TRCS (dBsm) TRCS (dBsm) 10 10.00 0 0.00 -10 -10.00 -20 -20.00 0 45 90 135 180 225 270 315 360 0 45 90 135 180 225 270 315 360 aspect (degrees) aspect (degrees) 6
M-1 Tank in Tree Clutter Scene • Scene incorporates dielectrically scaled wood and soil • Models coated with 4000-Å-thick sputtered Cu film 7
VHF/UHF RCS of Slicy, M-47, M-1, and Trees at 45° elevation Median RCS in dBsm free-space on ground plane w/o trees on ground plane w/ 8 trees 15.5 VV 16.3 VV 19.4 VV Slicy 15.1 HH 15.6 HH 19.9 HH 8.8 VV 8.8 VV 18.4 VV M-47 7.7 HH 11.4 HH 18.6 HH 10.2 VV 10.0 VV 18.4 VV M1 10.0 HH 12.5 HH 18.8 HH - - 17.7 VV Trees on ground plane - - 18.4 HH 8
Materials Issues •VHF/UHF dielectric constant of wood ranges from ε = 13 + i 3 to 68 + i 20 Scale model wood (aluminum-loaded epoxy): ε = 69 + i 10 •VHF/UHF dielectric constant of soil ranges from ε = 3 + i 0.5 to 24 + i 5 Scale model soil (carbon-loaded polyurethane): ε = 14.7 + i 1.1 Reflectivity of Scaled Model Soil Reflectivity of 1/35th Scale M-1 Coating 1 V-pol 1. 0000 H-pol 0. 9998 0.75 R ≈ 99.97% 0. 9996 R ª 46% 0.5 0. 9994 R ≈ 99.93% 0. 9992 0.25 R ª 21% 0. 9990 0 4000 8000 12000 16000 20000 24000 0 0 15 30 45 60 75 90 Thickness (Å) Elevation angle • 4000 Å sputtered Cu coating on M-1 model • Brewster angle of soil = 15° elev. • Skin depth of Cu film at 10 GHz = 8000 Å 9
VHF/UHF TRCS of M-1 Tank Free-space On smooth ground plane 10
VHF/UHF TRCS of M-1 Tank On ground plane with trees Trees only 11
VV-pol VHF/UHF ISAR Imagery of an M-1 Tank Range res. = 1.3 m, Cross range res. = 0.9 m, 90° aspect VV VV 50. 00 50. 00 100 100 90 90 44. 45 44. 45 80 80 40. 00 40. 00 70 70 34. 67 34. 67 60 60 30. 00 30. 00 50 50 40 40 30 30 20 20 10 10 f r ee space on gr ound pl ane 0 0 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 VV VV 50. 00 50. 00 100 100 90 90 44. 45 44. 45 80 80 40. 00 40. 00 70 70 34. 67 34. 67 60 60 30. 00 30. 00 50 50 40 40 30 30 20 20 10 10 on gr ound pl ane w i th tr ees tr ees onl y 0 0 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 12
HH-pol VHF/UHF ISAR Imagery of an M-1 Tank Range res. = 1.3 m, Cross range res. = 0.9 m, 90° aspect HH HH 50. 00 50. 00 100 100 90 90 44. 45 44. 45 80 80 40. 00 40. 00 70 70 34. 67 34. 67 60 60 30. 00 30. 00 50 50 40 40 30 30 20 20 10 10 f r ee space on gr ound pl ane 0 0 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 HH HH 50. 00 50. 00 100 100 90 90 44. 45 44. 45 80 80 40. 00 40. 00 70 70 34. 67 34. 67 60 60 30. 00 30. 00 50 50 40 40 30 30 20 20 10 10 on gr ound pl ane w i th tr ees tr ees onl y 0 0 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 13
Program Accomplishments • Established Radar Range to Acquire Calibrated VHF/UHF Signatures of Vehicles • Demonstrated Signature Validation with Method of Moments Code (CARLOS) • Developed Signal Processing Techniques for FOPEN ISAR Imaging • Developed Dielectrically Scaled Materials to Model Various Types of Soil & Wood • Fabricated Ground Planes Modeling Smooth, Moist Soil Surface • Demonstrated Ability to Construct Scale Model Tree Structures 14
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