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Characterization of EM wave diffusion in urban area in X-band

Study the diffusion of electromagnetic waves in an urban environment using 3D models of cities. Focus on multiple reflections and diffractions caused by buildings and edges.

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Characterization of EM wave diffusion in urban area in X-band

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  1. Presentator:Ngoc Truong Minh NGUYEN DRE/L2S (Supélec) - 3 rue Joliot Curie, 91192 Gif-sur-Yvette L2E (UPMC) - 4 place Jussieu, 75006 Paris mail:nnguyen@lss.supelec.fr-tel:01.69.85.15.71 Characterization of the diffusion of electromagnetic waves by an urban environment in X-band VNTélécom'09

  2. z Transmitter Receiver θ θ’ R R’ y O φ φ’ x Context and objectives • Context • Remote sensing: is the measurement/acquisition of the information about an object or a phenomenon by the no contact measuring between an instrument (usually a RADAR) and the object. • Instrument de mesure • SAR (Synthetic Aperture Radar): bistatic (transmitter and receiver are different) can overcome the limitations of conventional monostatic radar (non-discrete, easily confused ...) for the natural scene imageries or targets detection. • - This justifies our study of the diffusion bistatic by an urban area. • Objectives • The aim of the thesis is to develop 3D models of cities to study the diffusion in X-band (8 - 12 GHz). • - It takes into account the multiple reflections caused by the soil and buildings and diffractions by the edges of buildings. VNTélécom'09

  3. Contents • Representation of urban areas • Rays-tracing and UTD • Results • Perspectives VNTélécom'09

  4. How to define an urban area ? • Representation of urban areas • Rays-tracing and UTD • Results • Perspectives VNTélécom'09

  5. z O y εb μb x Lx εr μr Ly Representation of urban areas • An urban area sizes Lx x Ly • buildings: a set of randomly distributed rectangular parallelepipeds in this zone • ground: a smooth dielectric surface (weak roughness compared to the used wavelength) • streets: distances between the buildings • Electromagnetic characteristics • street (index r): εr, μr = μo = 4π.10-7 H / m • buildings (index b): εb, μb = μo = 4π.10-7 H / m VNTélécom'09

  6. Find methods to use ? • Representation of urban areas • Rays-tracing and UTD • Results • Perspectives VNTélécom'09

  7. z LOR LOR (Limit Of Reflection field) Zone 2 incident field + diffracted field Zone 1 LOI LOI (Limit Of Incident field) ki f' incident field + reflected field + diffracted field Zone 3 y diffracted field O Lx Dihedral Ly x Face n Face O Rays-tracing and UTD Geometrical Optic mathematical discontinuities Uniform Theory of the Diffraction Geometrical Theory of the Diffraction VNTélécom'09

  8. Hmm… How about the results ? • Representation of urban areas • Rays-tracing and UTD • Results • Perspectives VNTélécom'09

  9. x xr Transmitter z y Receiver yr i r φr O y εbéton μo Lx φi εsol μo Ly x Results • Problem: Calculate the diffracted field by the reflection (one or multiple) on the soil or the buildings and/or the diffraction on the edges of the buildings. • Four buildings • heights H = [8 14 10 12] m • length L = [5 6 5 6] m • width W = [4 5 7 8] m • εbéton = 7.31-j*0.36 • εsol = 28.51-j*12.84 • Transmitter:i = 28°, φi = 70°, sizes x = 20m, y = 20m • Receiver:r = 30°, φr = 270°, sizes xr = 100m, yr = 100m • Two radars placed at the same height (100m) VNTélécom'09

  10. Results The direct diffraction rays Rayon incident The rays influenced by one diffraction and two reflections The rays influenced by one diffraction then a reflection on the soil VNTélécom'09

  11. Results • The incident electromagnetic waveplane at frequency 10 GHz and | Einc | = 1 V / m Polarisation HV Polarisation VV Max |EHv|² = 3.70 dBm Min |EHv|² = -116.30 dBm Max |EVv|² = 13.69 dBm Min |EVv|² = -106.31 dBm VNTélécom'09

  12. Results • The contribution comes mainly from the field due to multiple reflections, the contribution of diffracted rays is lower. Polarisation VH Polarisation HH Max |EHh|² =14.32 dBm Min |EHh|² = -105.68 dBm Max |EVh|² = 4.29 dBm Min |EVh|² = -118.60 dBm VNTélécom'09

  13. Perspectives • Representation of urban areas • Rays-tracing and UTD • Results • Perspectives VNTélécom'09

  14. Perspectives • To obtain an average value of the diffused field in a given direction, it should be calculated several possible configurations for the broadcast and then generate the average field. • The applications are: • Characterization of the diffracted field by arbitrary urban zones. • SAR imageries or targets detection in this environment. VNTélécom'09

  15. Bibliographies 1- S. Meric, G. Chassay, O. Bechu and T. Tenoux,’’Propagation prediction calculation used for SAR imaging Urban area’’, Electronics Letters, 34(11): 1147-1149, mai 1998 2- J.M. Berenyi Tajbakhsh, M.J. Kim and R.E. Burge,’’Images of urban areas by a synthetic aperture radar simulator’’, Conf. on SAR data processing for remote sensing, Rome, Italy, p.290-300, septembre 1974 3- R .J. Luebbers,’’Finite conductivity uniform GTD versus knife edge diffraction in prediction of propagation path loss’’, Antennas and Propagation, IEEE Transactions on [legacy, pre - 1988], p.70-76, janvier 1984 4- R.G. Kouyoumjian,’’A uniform geometrical theory of diffraction for an edge in a perfectly conducting surface’’, Proc. IEEE 62, p.1448-1461, novembre 1974 VNTélécom'09

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