Industrial radar sensor arrays and their applications

1. Industrial radar sensor arrays and their applications October 04, 2011 P. Vainikainen, V. Mikhnev, Ye. Maksimovitch, M.-K. Olkkonen Aalto University School of Electrical Engineering SMARAD Dept. of Radio Science and Engineering P.O. Box 13000, FI-00076 AALTO Finland valeri.mikhnev@aalto.fi

2. Outline • Wideband technologies • UWB antennas and antenna arrays • Signal processing techniques • Experimental examples • Summary

3. Wideband technologies • Impulse technology • georadar • subsurface radar • level gauges • Frequency-swept sine-wave technology • moisture sensors • level gauges • thickness gauges • sensors for material characterization • anti-collision radar • M-sequence technology • attempts to combine advantages of the both technologies above • very high speed of data acquisition

4. Tapered-slot UWB antenna R-cards Antenna width 120 mm Antenna length 230 mm Substrate FR-4 R-cards 200 Ω/□ Elliptical form of flares Width of microstrip 1.8 mm stub length 10 mm Slotline width 0.5 mm stub length 13 mm The both stubs are circular 85º sectors.

5. Tapered-slot UWB antenna E-field E-plane Unloaded antenna Loaded antenna

6. Tapered-slot UWB antenna

7. transmitting antenna receiving antenna UWB antenna arrays Double-ladder Zigzag array array 3 cm direction of scan

8. V–V H–H H–V V–H UWB antenna arrays G. Alli et al, “Data processing for mine-detection polarimetric ground penetrating radar array,” in Proc. of the 10th Int. Conf. on Ground Penetrating Radar,2004, Delft, 4p.

9. Signal processing Evaluation and discrimination Time-frequency analysis Natural complex resonances Set of features Wigner-Ville transform Two subtasks of interest: Detection of reflecting targets by the sensor Evaluation of parameters of the target and its discrimination Signal component ...........................

10. Signal processingfor the case of GPR Extraction of amplitude vs time Intensity of pixel B-SCAN Color of pixel Extraction of phase vs time Removal of the phase due propagation

11. Phase profile retrieval • Determination of dominant peak by magnitude in every A-scan and its filtering by the one-dimensional Gaussian filter yielding partial range profile by amplitude. • Derivation of the phase profile corresponding to the peak using • where L is position of the peak. • Calculation of the residual of the signal after subtracting the filtered dominant peak. • Return to the step 1 until given number of peaks is reached or all peaks above given threshold are processed. • Summing up obtained profiles. Derivation of both amplitude and phase versus time.

12. Building GPR image Color map 90 180 0 270 B-scan in phase Image B-scan in amplitude Threshold Final image

13. Experimental results Network analyzer • Experimental setup: • Network analyzer Agilent E5071B • Frequency range 1.3 – 6.5 GHz • Tapered-slot antennas T-R antenna pair Metal rods In sand Conventional grayscale image Pure phase image Amplitude-phase image

14. Experimental results Metal rod (orthogonal polarization) Plastic pipe (parallel polarization) Void in sand PMN mine simulant in sand

15. Summary A modified UWB tapered-slot antenna exhibiting high wideband gain and low level of sidelobes has been developed. A novel microwave imaging method based on separate determination and representation of amplitude and phase profiles has been proposed. Subsurface objects can be detected by amplitude and discriminated by phase in a common color image. The retrieval of the phase profile can be applied to other tasks of microwave sensing. So, air gaps between shotcrete and rocks in tunnels can be detected and recognized by this method.