Download Performance Enhanced High Speed UWB  GPR System  for Buried Rebar Detection Tian Xia, Anbu Venkatachalam, Yu Zhang Dylan Burns, Dryver Huston

Performance Enhanced High Speed UWB GPR System for Buried Rebar Detection
Tian Xia, Anbu Venkatachalam, Yu Zhang
Dylan Burns, Dryver Huston
School of Engineering
University of Vermont
March 19, 2013
• Motivation
• UWB GPR Hardware Improvement
• Test Setup
• Radar Data Processing Improvement
• Conclusion
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Design Objectives: To improve performance of an air‐launched GPR developed for bridge deck, roadway and railroad subsurface structure characterizations.
 Hardware:
A new pulsar circuit to improve signal dynamic range
 Signal processing:
‐ Time and frequency characterizations of GPR signals;
‐ Adaptive magnitude scaling;
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 Different subsurface medias different dielectric constants
 different EM waves strength and travel velocity;  The reflected EM signals can thus be used to characterize subsurface conditions.
condition. 6
Hardware: ‐High voltage low ringing pulse generator; ‐High fidelity UWB antennas;
‐Real time high speed data acquisition unit; ‐Adaptive FPGA controller; Software: ‐
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High throughput data acquisition and transmission;
Multithread parallel signal processing;
Radar signal characterization algorithms;
Graphic user interface. 7
500 ps ~ 1.2 ns Gaussian pulse; 20 V‐Vpp; Pulse amplitude/ringing > 20 dB
Gaussian pulse upon ‐12 dB attenuation
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‐ Real time high speed data acquisition: 8Gsps, 10‐bit; ‐ Quad‐core processor for multi‐thread parallel data acquisition and transmission ;
‐ High pulse repetition frequency (up to 30 KHz) to achieve fine spatial resolution. 9
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 Feature characterizations ‐ STFT and noise filtering  Vibration effect correction
 Systematic noise reduction
 Radio frequency interference reduction
 Adaptive magnitude scaling Fourier transform has been widely used for signal spectrum analysis. Main limitation: the signal time information is lost in transforming to frequency domain. GPR operation involves subsurface features inspection which change with time leading to non‐stationary reflection signals being collected.
Short Time Fourier Transform (STFT) implements local Fourier Transform on data that are divided into smaller windows
 time and frequency characterizations with both time and frequency information are maintained. 12
Applying Short Time Fourier Transform to perform time and frequency characterizations
Rebar reflection signal: located at ~ 20 ns, spectrum ~2 GHz; The major noise signals spectrum >2 GHz or < 0.5 GHz
 determine bandpass filter specifications 13
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Average calculation + Average subtraction + Bandpass filtering
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 The new HW and SW designs improve GPR performance: High voltage pulse  high dynamic range
STFT and adaptive scaling  enhanced signal features
 The laboratory tests show encouraging results. Future work
 To conduct field test for further design improvements;  Radar data processing automation.
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