Traditional impulse Ground Penetrating Radar (GPR) systems use time-domain measurements of the reflected waves within the investigated objects. A Stepped Frequency Continuous Wave (SFCW) system collects data in the frequency domain and converts the data to time-domain data through computer processing. Until recently, the time-consuming calculations associated with the real-time inverse Fourier transforms in SFCW systems limited its application. Thanks to faster processing capabilities available nowadays, this limitation no longer applies to GPR. The experimental work on representative concrete structures presented in this paper shows a systematic comparison of a new SFCW GPR system with traditional impulse radar systems. The results illustrate that SFCW technology combines the highest resolution in the detection of shallow targets, with a very broad detection range. At the same time, the system is very fast, both in terms of data display as well as data sharing. Therefore, we are concluding that experts, civil engineers and contractors will be able to rely on a higher probability of detection and higher productivity using just one SFCW test system in the future. Proceq GPR Live by Proceq is the world's first and only handheld portable Ground Penetrating Radar for concrete scanning and imaging applications that utilizes Stepped-Frequency Continuous-Wave radar technology and a user-friendly, gesture-based touch interface on Apple iPad, as well as secure cloud-based features enabling collaboration from anywhere, anytime. It provides unparalleled penetration depth (up to 70 cm of dry concrete) and data and image clarity thanks to its ultrawideband radar subsystem. Find out more at http://bit.ly/ProceqGPRLive

1. Looking into concrete – multiple frequency
usage in radar products to detect structural
parameters and defects faster and more
accurately
15th Asia-Pacific Conference for Non-Destructive Testing (APCNDT2017)
Singapore, November 15, 2017
G. Tronca, S. Lehner, L. Raj, I. Tsalicoglou, J. Meier*, R. Mennicke
Proceq SA and Proceq Asia Pte Ltd.
© Proceq 2017 1

2. 1
Overview
Traditional Ground Penetrating Radar (“GPR”)
Stepped-frequency continuous-wave ("SFCW") GPR
Experimental setup and validation
Observations and conclusions
© Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 2
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3
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3. 1
Overview
Traditional Ground Penetrating Radar (“GPR”)
Stepped-frequency continuous-wave ("SFCW") GPR
Experimental setup and validation
Observations and conclusions
© Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 3
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3
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4. © Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 4
As-built
verification
Integrity
assessment
Hit prevention
(e.g. coring)
Ground Penetrating Radar (GPR) is used for the
reliable detection of targets
• Targets: features, flaws
• In structural concrete:
 Metallic reinforcements
 Post-tensioning ducts
 Plastic pipes
 Air voids
 Object boundaries

5. © Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 5
GPR detects discontinuities of dielectric
properties caused by the targets
• At boundaries of
discontinuities:
 Partial transmission
 Partial reflection
• Round-trip travel time of
the wave / reflection
Depth
Time
“hyperbola”
“Time of flight method”

6. Non-migrated view Migrated view
© Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 6
Estimated locations and depths of targets are
represented in a B-scan

7. © Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 7
• Adverse signal effects:
 Attenuation
 Scattering
 Loss
• …depend on:
 Antenna frequency
 Concrete properties
Traditional impulse GPR devices broadcast
electromagnetic pulses at one central frequency
Antenna
frequency
Adverse signal
effects
Penetration
depth
Sensitivity to
discontinuities
Resolution

8. © Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 8
Better data can be gathered from deeper within
the inspected objects
Structural concrete
applications:
• f = 1.0 … 2.6 GHz
• Max. depth ≈ 0.5 m
Detectable objectssmall large
Ultra wideband technology
Penetrationdepth
070cm
2.6 GHz 2.0 GHz 1.6 GHz 1.0 GHz
Frequency

9. 1
Overview
Traditional Ground Penetrating Radar (“GPR”)
Stepped-frequency continuous-wave ("SFCW") GPR
Experimental setup and validation
Observations and conclusions
© Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 9
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3
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10. © Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 10
Stepped frequency
Proceq’s stepped-frequency continuous wave
(SFCW) resolves the traditional trade-off
• Multiple frequency steps
• Ultra-wideband range of
modulated frequencies
 Design: 0.2 … 4.0 GHz
 Net: 0.9 … 3.5 GHz
Continuous wave
Proceq’s electronics design
optimizations
• Continuous broadcasting
of electromagnetic waves
• Data gathering in
the frequency domain
• Faster real-time inverse
Fourier transforms
• Maximum signal
acquisition time > 2x
• High signal-to-noise ratio

11. © Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 11
With SFCW, better data can be gathered from
deeper within the inspected objects
“Looking into
concrete”
with a single
SFCW GPR
device
Detectable objectssmall large
Ultra wideband technology
Penetrationdepth
070cm
2.6 GHz 2.0 GHz 1.6 GHz 1.0 GHz
Frequency
4.0 GHz 0.2 GHz
Combine all
frequency responses

12. • Ultrawideband
SFCW antenna
• Optimized
electronics design
• Ergonomic handheld
scanning cart
• iOS tablet
• Data-processing
algorithms
• User-friendly app
© Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 12
Proceq GPR Live is the world’s first SFCW GPR
system for structural concrete applications
ShareShare
Collaboration
Webtool
SEGY
JPEG

13. 1
Overview
Traditional Ground Penetrating Radar (“GPR”)
Stepped-frequency continuous-wave ("SFCW") GPR
Experimental setup and validation
Observations and conclusions
© Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 13
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3
4

14. © Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 14
Validation of SFCW GPR involved systematic
testing with a clear process
Concrete block design GPR scanning
Data export
(if available)
Data post-
processing
SEGY

15. © Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 15
Four different concrete blocks were designed to
represent realistic configurations
1 2
3 4

16. © Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 16
Hilti PS-1000
GSSI StructureScan
Mini XT
Proceq GPR Live
GPR technology Pulsed Pulsed SFCW
Nominal frequency 2.0 GHz 2.7 GHz 0.2 … 4.0 GHz
Acquisition time 6 ns 9 ns 20 ns
Raw data export  ✓ ✓
Data post-processing Hilti PROFIS Detection GPR-SLICE GPR-SLICE
The two traditional GPR devices are currently
seen as state-of-the-art

17. © Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 17
Case 1
• Five Ø 16 mm rebars
• Flat back wall at 60 cm
1

18. © Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 18
Case 1
Hilti PS-1000
All rebars detected; however, the back wall is out of range.
1

19. © Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 19
Case 1
GSSI StructureScan Mini XT
All rebars detected; however, the back wall is out of range.
1

20. © Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 20
Case 1
Proceq GPR Live
All rebars and the back wall detected.
1

21. © Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 21
Case 2
• No rebars
• Void 150 mm × 70 mm
• V-shaped back wall
2

22. © Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 22
Case 2
Hilti PS-1000
Void detected with spurious noise; back wall undetected.
2

23. © Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 23
Case 2
GSSI StructureScan Mini XT
Void detected, but most of the back wall remains out of range.
2

24. © Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 24
Case 2
Proceq GPR Live
All targets detected without any spurious noise.
2

25. © Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 25
Case 3
• Ø 16 mm rebar mesh
120 mm × 120 mm
• Void 150 mm × 70 mm
• V-shaped back wall
3

26. © Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 26
Case 3
Hilti PS-1000
Only the shallow rebar mesh was detected.
3

27. © Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 27
Case 3
GSSI StructureScan Mini XT
Beyond the rebar mesh, inexistent targets were falsely detected.
3

28. © Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 28
Case 3
Proceq GPR Live
All targets detected unambiguously.
3

29. © Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 29
Case 4
• Two mats of reinforcement
Ø 12 mm rebar mesh
150 mm × 150 mm
• Void Ø 120 mm
• PT duct
• Flat back wall at 50 cm
4

30. © Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 30
Case 4
Hilti PS-1000
Fails to reach the back wall and its rebar mesh, and to detect the void.
4

31. © Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 31
Case 4
GSSI StructureScan Mini XT
Covers a larger depth than the Hilti PS-1000, but ultimately with similar results.
4

32. © Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 32
Case 4
Proceq GPR Live
All targets detected, including the deep rebar mesh and the back wall.
4

33. © Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 33
Case 4 (extended)
Proceq GPR Live
First layer rebar
Duct
Defect
Back wall
Second layer rebar
Hidden area

34. 1
Overview
Traditional Ground Penetrating Radar (“GPR”)
Stepped-frequency continuous-wave ("SFCW") GPR
Experimental setup and validation
Observations and conclusions
© Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 34
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3
4

35. © Proceq 2017 Looking into concrete – stepped-frequency continuous-wave (SFCW) ground-penetrating radar (GPR) 35
Detection Traditional GPR devices SFCW GPR (Proceq GPR Live)
Penetration
depth
Shallow targets ✓ ✓
Deeper targets  ✓
Resolution,
accuracy, and
clarity
Weak reflectors  ✓
Spurious noise ✓ 
False positives ✓ 
SFCW GPR represents a major breakthrough in structural concrete inspection.
SFCW technology has proven to effectively
resolve the traditional GPR trade-off