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@ARTICLE{Jadoon:15382,
      author       = {Jadoon, K.Z. and Lambot, S. and Slob, E.C. and Vereecken,
                      H.},
      title        = {{A}nalysis of {H}orn {A}ntenna {T}ransfer {F}unctions and
                      {P}hase-{C}enter {P}osition for {M}odeling {O}ff-{G}round
                      {GPR}},
      journal      = {IEEE transactions on geoscience and remote sensing},
      volume       = {49},
      issn         = {0196-2892},
      address      = {New York, NY},
      publisher    = {IEEE},
      reportid     = {PreJuSER-15382},
      pages        = {1649 - 1662},
      year         = {2011},
      note         = {This work was supported by the Forschungszentrum Julich
                      GmbH (Germany), the Universite Catholique de Louvain and
                      Fonds de la Recherche Scientifique (Belgium), Delft
                      University of Technology (The Netherlands), and DIGISOIL
                      project financed by the European Commission under the
                      Seventh Framework Program for Research and Technological
                      Development, Area "Environment," Activity 6.3 "Environmental
                      Technologies."},
      abstract     = {The antenna of a zero-offset off-ground ground-penetrating
                      radar can be accurately modeled using a linear system of
                      frequency-dependent complex scalar transfer functions under
                      the assumption that the electric field measured by the
                      antenna locally tends to a plane wave. First, we analyze to
                      which extent this hypothesis holds as a function of the
                      antenna height above a multilayered medium. Second, we
                      compare different methods to estimate the antenna phase
                      center, namely, 1) extrapolation of peak-to-peak reflection
                      values in the time domain and 2) frequency-domain
                      full-waveform inversion assuming both frequency-independent
                      and -dependent phase centers. For that purpose, we performed
                      radar measurements at different heights above a perfect
                      electrical conductor. Two different horn antennas operating,
                      respectively, in the frequency ranges 0.2-2.0 and 0.8-2.6
                      GHz were used and compared. In the limits of the antenna
                      geometry, we observed that antenna modeling results were not
                      significantly affected by the position of the phase center.
                      This implies that the transfer function model inherently
                      accounts for the phase-center positions. The results also
                      showed that the antenna transfer function model is valid
                      only when the antenna is not too close to the reflector,
                      namely, the threshold above which it holds corresponds to
                      the antenna size. The effect of the frequency dependence of
                      the phase-center position was further tested for a
                      two-layered sandy soil subject to different water contents.
                      The results showed that the proposed antenna model avoids
                      the need for phase-center determination for proximal soil
                      characterization.},
      keywords     = {J (WoSType)},
      cin          = {IBG-3},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IBG-3-20101118},
      pnm          = {Terrestrische Umwelt},
      pid          = {G:(DE-Juel1)FUEK407},
      shelfmark    = {Geochemistry $\&$ Geophysics / Engineering, Electrical $\&$
                      Electronic / Remote Sensing},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000289906200014},
      doi          = {10.1109/TGRS.2010.2089691},
      url          = {https://juser.fz-juelich.de/record/15382},
}