An Airborne Millimeter-Wave FM-CW Radar for Thickness Profiling of Freshwater Ice

• Main Author: Yankielun, Norbert E.
• Other Authors: THAYER SCHOOL OF ENGINEERING HANOVER NH
• Format: Text
• Language: English
• Published: 1992
• Subjects: Active & Passive Radar Detection & Equipment; *CONTINUOUS WAVE RADAR; TEST AND EVALUATION; VELOCITY; SIGNAL PROCESSING; FREQUENCY; OUTPUT; POWER LEVELS; MEASUREMENT; RATIOS; THICKNESS; VOLUME; SCATTERING; ACQUISITION; REAL TIME; SPECIFICATIONS; WATER; PROCESSING; RESOLUTION; BUBBLES; SHEETS; SIGNALS; SURVEYS; PULSES; ICE; HELICOPTERS; SNOW COVER; SNOW; TRAFFICABILITY; PONDS; SHORT PULSES; LAKES; ROUGHNESS; RIVERS; NOISE; LOSSES; RADIO EQUIPMENT; DATA ACQUISITION; SAFETY; BROADBAND; PROFILES; CORRELATION; BOUNDARIES; SURFACES; TIME; BOREHOLES; RADAR; MILLIMETER WAVES; PROTOTYPES; ACCURACY; RATES; SURFACE ROUGHNESS; FIELD TESTS; SIGNAL TO NOISE RATIO; STRUCTURES; Ice Sheet
• Online Access: http://www.dtic.mil/docs/citations/ADA259368; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA259368

The ability to profile rapidly and accurately the structure of freshwater ice down to a thickness of a few centimeters over large surfaces of frozen ponds, lakes and rivers has wide military, industrial, commercial and recreational application, including safety and trafficability surveys. A prototype broadband millimeter wave (26.5 to 40 GHz) Frequency Modulated- Continuous Wave (FM-CW) radar, employing real-time data acquisition and Digital Signal Processing (DSP) techniques, has been developed for continuously recording the thickness profile of freshwater ice. Thickness resolution is better than 3 cm +/-10%, which improves on short-pulse and FM-CW radars operating at frequencies less than 10 GHz. These other radars have a best reported thickness resolution of approximately 10 cm with a +/-10% accuracy; this is insufficient because a freshwater ice sheet as thin as 5 cm, floating on water, can be safely traversed by an individual of average weight. System specifications include a 15-dBm output RF (Radio Frequency) power level, a 0. 066-second sweep rate and less than a 50dB Signal-to-Noise Ratio (SNR). This radar was tested on the ground and from a helicopter at heights of up to 7 m above ice surfaces at speeds up to 40 km/hr. Pond and river ice sheets between 3 and 35 cm thick, with and without fresh snow cover, and with minimal surface roughness have been profiled. Results have shown direct correlation between radar and borehole thickness measurements. Losses from volume scattering by imbedded air bubbles did not significantly affect the system's capability to discern the air/ice and ice/water scattering boundaries. Field tests, Ice safety, Millimeter wave radar, Ice, Ice thickness profiling.