1. University of Brasília Laboratory of Array Signal Processing 1 Improved Landing Radio Altimeter for Unmanned Aerial Vehicles based on an Antenna Array Ronaldo S. Ferreira Júnior, Marco A. M. Marinho, Kefei Liu, João Paulo C. Lustosa da Costa, Arthur V. Amaral, and Hing Cheung So University of Brasília (UnB) Department of Electrical Engineering (ENE) Laboratory of Array Signal Processing PO Box 4386 Zip Code 70.919-970, Brasília - DF

2. University of Brasília Laboratory of Array Signal Processing 2 Outline   Motivation   Traditional radio altimeter   Antenna array based radio altimeter   Simulation results   Conclusions

3. University of Brasília Laboratory of Array Signal Processing 3 Outline   Motivation   Traditional radio altimeter   Antenna array based radio altimeter   Simulation results   Conclusions

4. University of Brasília Laboratory of Array Signal Processing 4 Motivation (1)  Applications  Landing and approaching of Unmanned Aerial Vehicles  Detect dangerous obstacles  Manned operations where life can be put in risk  Drawback  Only the main power component reflected component Multipath components are not taken into account  Antenna array based Radio Altimeter  The multipath components are estimated.  The ground can be mapped.

5. University of Brasília Laboratory of Array Signal Processing 5 Motivation (2)   Example with 3 MPCs Which one is detected?

6. University of Brasília Laboratory of Array Signal Processing 6 Motivation (3)   By detecting only the red component:   A crash is prevented.   How to detect all multipath components?   By detecting the Direction of Arrival (DoA) and the Time Delay of Arrival (TDoA) of the MPCs

7. University of Brasília Laboratory of Array Signal Processing 7 Motivation (4)   Solution for Direction of Arrival (DOA) estimation   Another candidate solution: Rotating antenna   Advantage DOA detection according to the antenna position   Drawback: Heavy weighted, large sized and slow scanning   Proposed solution: Antenna arrays   Advantages: Compact, power saving and light weighted   Drawback: Complex software and complex hardware

8. University of Brasília Laboratory of Array Signal Processing 8 Outline   Motivation   Traditional radio altimeter   Antenna array based radio altimeter   Simulation results   Conclusions

9. University of Brasília Laboratory of Array Signal Processing 9 Traditional Radio Altimeter (1)   General information   Frequency Modulated–Continuous Wave (FM-CW) radio altimeter   Uses saw-tooth or triangle wave as the modulating signal   Altitude-to-frequency conversion the time-delayed wave mixed with the transmitted wave   Not possible to distinguish the MPCs

10. University of Brasília Laboratory of Array Signal Processing 10   Simplified block diagram of a traditional radio altimeter for UAVs Traditional Radio Altimeter (2)

11. University of Brasília Laboratory of Array Signal Processing 11 Outline   Motivation   Traditional radio altimeter   Antenna array based radio altimeter   Simulation results   Conclusions

12. University of Brasília Laboratory of Array Signal Processing 12   Simplified block diagram of an antenna array based radio altimeter Antenna Array based Radio Altimeter (1)

13. University of Brasília Laboratory of Array Signal Processing 13 Antenna Array based Radio Altimeter (2)   Candidate solutions for the signal processing block   MUSIC High-resolution  More computational effort    ESPRIT Closed-form solution  Worse resolution than MUSIC  Array with shift invariance structure 

14. University of Brasília Laboratory of Array Signal Processing 14 Antenna Array based Radio Altimeter (3) [1]: J. P. C. L. da Costa, A. Thakre, F. Roemer, and M. Haardt, “Comparison of model order selection techniques for high-resolution parameter estimation algorithms”, in. Proc. 54 th International Scientific Colloquium (IWK), Ilmenau, Germany, Sept. 2009. The model order d can be estimated based on [1]. We consider it as known.  Matrix data model

15. University of Brasília Laboratory of Array Signal Processing 15 Antenna Array based Radio Altimeter (4)   Selection matrices and   To estimate the spatial frequencies (ESPRIT)

16. University of Brasília Laboratory of Array Signal Processing   Estimation of Signal Parameters via Rotation Invariance Techniques ESPRIT 16   The steering matrix A and the first d eigenvectors U of the covariance matrix generate the same subspace   Note that U s is related to the low-rank approximation.   Spatial frequencies Antenna Array based Radio Altimeter (5)

17. University of Brasília Laboratory of Array Signal Processing 17 Outline   Motivation   Traditional radio altimeter   Antenna array based radio altimeter   Simulation results   Conclusions

18. University of Brasília Laboratory of Array Signal Processing 18 Simulation Results (1)

19. University of Brasília Laboratory of Array Signal Processing 19 Simulation Results (2)

20. University of Brasília Laboratory of Array Signal Processing 20 Simulation Results (3)

21. University of Brasília Laboratory of Array Signal Processing 21 Outline   Motivation   Traditional radio altimeter   Antenna array based radio altimeter   Simulation results   Conclusions

22. University of Brasília Laboratory of Array Signal Processing 22 Conclusions   The antenna array based radio altimeter   Ground mapping and imaging   Ground inclination and obstacle detection   Electronic receiving lobe sweep   Light weight and small sized compared to a mechanical scanning radar

23. University of Brasília Laboratory of Array Signal Processing 23 Thank you for your attention! Prof. Dr.-Ing. João Paulo C. Lustosa da Costa University of Brasília (UnB) Department of Electrical Engineering (ENE) Laboratory of Array Signal Processing PO Box 4386 Zip Code 70.919-970, Brasília – DF E-mail: joaopaulo.dacosta@ene.unb.br