ground-based fmcw radar measurements: a summary of the nasa clpx data h.p. marshall institute of...
DESCRIPTION
Br ief FMCW Theory II Linear frequency chirp transmitted (T) Received signal (R) “mixed” with transmitted wave before signal acquisition Recorded signal contains the sum and difference frequencies from T + R Frequency differences from reflectors linearly related to the distance to targetTRANSCRIPT
Ground-Based FMCW radar measurements: a summary of the NASA CLPX data
H.P. Marshall Institute of Arctic and Alpine Research, Univ. of ColoradoGary Koh, Cold Regions Research and Engineering Lab, New HampshireRick Forster, Department of Geography, University of Utah
Brief FMCW Theory I
+ =
Brief FMCW Theory II
• Linear frequency chirp transmitted (T)
• Received signal (R) “mixed” with transmitted wave before signal acquisition
• Recorded signal contains the sum and difference frequencies from T + R
• Frequency differences from reflectors linearly related to the distance to target
cd
vd
BT
dFTsw
plw
222
Windowed FFT, zero-padded, normalized by DC-coupling, power from
surface calibration
Filter instrumentation-related signals
• Locations where mean of signal > 5x mean deviation found
• Mean trace at these depths subtracted from scan
Depth Calibration
• Metal reflectors placed at known depths
• Accurate depth scale, will also be used to calculate attenuation
Michigan Ridge, North Park, Feb 21,2003
Berthud Pass, February 22, 2003
Relationship of FMCW signal manual measurements
Density profile vs radar
In-situ Dielectric Properties
In-situ Dielectric Properties II
LSOS Feb 19, 2002, C-Band: 2-6 GHz
DRY SNOWPACK
LSOS Feb 19, 2002, X-Band: 8-12 GHz
DRY SNOWPACK
LSOS Feb 19, 2002, Ku-Band: 14-18 GHz
DRY SNOWPACK
LSOS March 26, 2002, C-Band: 2-6 GHz
WET SNOWPACK
LSOS March 26, 2002, X-Band: 8-12 GHz
WET SNOWPACK
LSOS March 26, 2002, Ku-Band: 14-18 GHz
WET SNOWPACK
Effect of incidence angle
oc
rc
r
c
oeff P
PRR
4
Effect of incidence angle II
Conclusions • FMCW signal strongly related to
in-situ dielectric measurements• Resolution highest at Ku-Band,
but little penetration if wet• Incidence angle measurements
indicate surface scattering dominates below ~15 deg and volume scattering above 30
• Preliminary comparison with FMCW measurements at more narrow bandwidths encouraging
Acknowledgements
NASA Earth System Science Fellowship
CRREL
Kelly Elder, Don Cline
Nate Mullheren