Ponències/Comunicacions de congressos
http://hdl.handle.net/2117/654
2017-02-20T04:07:36ZAdvanced millimeter wave technology for mobile communications
http://hdl.handle.net/2117/100925
Advanced millimeter wave technology for mobile communications
Pradell i Cara, Lluís; Corbella Sanahuja, Ignasi; Comerón Tejero, Adolfo; Bará Temes, Francisco Javier; Artal, E.; Torres Torres, Francisco; Purroy, Francesc; Barlabe Dalmau, Antoni; Sales, V.
2017-02-13T13:49:08ZPradell i Cara, LluísCorbella Sanahuja, IgnasiComerón Tejero, AdolfoBará Temes, Francisco JavierArtal, E.Torres Torres, FranciscoPurroy, FrancescBarlabe Dalmau, AntoniSales, V.Development of self-calibration techniques for on-wafer and fixtured measurements: a novel approach
http://hdl.handle.net/2117/100692
Development of self-calibration techniques for on-wafer and fixtured measurements: a novel approach
Pradell i Cara, Lluís; Purroy Martín, Francesc; Cáceres, M.
Network Analyzer self-calibration techniques - TRL, LMR, TAR- are developed, implemented and compared in several transmission media. A novel LMR (Line-Match-Reflect) technique based on known LINE and REFLECT Standards, is proposed and compared to conventional LMR (based on known LINE and MATCH Standards) and other techniques (TRL, TAR). They are applied to on-wafer S-parameter measurement as well as to coaxial, waveguide and microstrip media. Experimental results up to 40 GHz are presented.
2017-02-08T14:37:53ZPradell i Cara, LluísPurroy Martín, FrancescCáceres, M.Network Analyzer self-calibration techniques - TRL, LMR, TAR- are developed, implemented and compared in several transmission media. A novel LMR (Line-Match-Reflect) technique based on known LINE and REFLECT Standards, is proposed and compared to conventional LMR (based on known LINE and MATCH Standards) and other techniques (TRL, TAR). They are applied to on-wafer S-parameter measurement as well as to coaxial, waveguide and microstrip media. Experimental results up to 40 GHz are presented.SMOS simplified iterative full-pol brightness temperature retrieval
http://hdl.handle.net/2117/100615
SMOS simplified iterative full-pol brightness temperature retrieval
Durán Martínez, Israel; Lin, Wu; Torres Torres, Francisco; Corbella Sanahuja, Ignasi; Duffo Ubeda, Núria; Martín Neira, Manuel
SMOS is the acronym for the Soil Moisture and Ocean Salinity mission by the European Space Agency (ESA) [1]. Its single payload, the Microwave Imaging Radiometer using Aperture Synthesis (MIRAS), was successfully launched in November 2009. Along more than six years of operation, SMOS calibration and imaging algorithms have undergone a continuous evolution to further improve the accuracy of the retrieved geophysical parameters for a variety of scientific applications related with soil moisture and ocean salinity [2]. This paper analyzes a simplified iterative image reconstruction method that exclusively takes into account the dominant terms in the full-polarimetric equation [3]. This simplified method, that reduces computation time up to 50% at the cost of small radiometric performance degradation, is useful to the L1 teams to fine tune the calibration of the instrument when processing a large amount of data is required.
2017-02-07T10:50:19ZDurán Martínez, IsraelLin, WuTorres Torres, FranciscoCorbella Sanahuja, IgnasiDuffo Ubeda, NúriaMartín Neira, ManuelSMOS is the acronym for the Soil Moisture and Ocean Salinity mission by the European Space Agency (ESA) [1]. Its single payload, the Microwave Imaging Radiometer using Aperture Synthesis (MIRAS), was successfully launched in November 2009. Along more than six years of operation, SMOS calibration and imaging algorithms have undergone a continuous evolution to further improve the accuracy of the retrieved geophysical parameters for a variety of scientific applications related with soil moisture and ocean salinity [2]. This paper analyzes a simplified iterative image reconstruction method that exclusively takes into account the dominant terms in the full-polarimetric equation [3]. This simplified method, that reduces computation time up to 50% at the cost of small radiometric performance degradation, is useful to the L1 teams to fine tune the calibration of the instrument when processing a large amount of data is required.Impact of amplitude calibration errors on SMOS global images
http://hdl.handle.net/2117/99432
Impact of amplitude calibration errors on SMOS global images
Durán Martínez, Israel; Corbella Sanahuja, Ignasi; Torres Torres, Francisco; Duffo Ubeda, Núria; Oliva, Roger; Martín Neira, Manuel
Some of the artifacts observed in SMOS brightness temperature images are originated in an inconsistency between correlation and antenna temperature calibration errors, which produces a multiplicative bias that scales with the scene mean antenna temperature. Its most important effect, although not the only one, is a land-to-sea contamination near coastal areas, which cannot be easily mitigated by post-processing correction techniques. A simplified end-to-end simulator allows introducing separate errors in both antenna temperature and correlation, thus
providing an important insight on this problem and helping understanding its origin. Results from simulations compare very well with actual results from measured data.
2017-01-17T11:15:35ZDurán Martínez, IsraelCorbella Sanahuja, IgnasiTorres Torres, FranciscoDuffo Ubeda, NúriaOliva, RogerMartín Neira, ManuelSome of the artifacts observed in SMOS brightness temperature images are originated in an inconsistency between correlation and antenna temperature calibration errors, which produces a multiplicative bias that scales with the scene mean antenna temperature. Its most important effect, although not the only one, is a land-to-sea contamination near coastal areas, which cannot be easily mitigated by post-processing correction techniques. A simplified end-to-end simulator allows introducing separate errors in both antenna temperature and correlation, thus
providing an important insight on this problem and helping understanding its origin. Results from simulations compare very well with actual results from measured data.Mitigation of cross-polar antenna pattern errors in SMOS: simplified approach
http://hdl.handle.net/2117/99429
Mitigation of cross-polar antenna pattern errors in SMOS: simplified approach
Durán Martínez, Israel; Torres Torres, Francisco; Corbella Sanahuja, Ignasi; Duffo Ubeda, Núria; Lin, Wu; Martín Neira, Manuel
This paper analyzes a simplified image reconstruction method that exclusively takes into account the dominant antenna pattern terms to model image inversion artifacts and mitigate SMOS polarimetric spatial bias over the Ocean. This simplified method, that reduces computation time at the cost of small radiometric performance degradation, is useful to the L1 teams to process a large amount of data when full radiometric accuracy is not required (e.g. stability assessments).
2017-01-17T11:05:33ZDurán Martínez, IsraelTorres Torres, FranciscoCorbella Sanahuja, IgnasiDuffo Ubeda, NúriaLin, WuMartín Neira, ManuelThis paper analyzes a simplified image reconstruction method that exclusively takes into account the dominant antenna pattern terms to model image inversion artifacts and mitigate SMOS polarimetric spatial bias over the Ocean. This simplified method, that reduces computation time at the cost of small radiometric performance degradation, is useful to the L1 teams to process a large amount of data when full radiometric accuracy is not required (e.g. stability assessments).Millimeter-wave aperture synthesis radiometry for snow and ice mapping
http://hdl.handle.net/2117/98424
Millimeter-wave aperture synthesis radiometry for snow and ice mapping
Harvey, A.R.; Greenaway, A.H.; Camps Carmona, Adriano José; Corbella Sanahuja, Ignasi; Torres Torres, Francisco; Bara Temes, Francisco Javier; Martín Neira, Manuel
An outline design for a dual-band mm-wave polarimetric SAIR has been presented and is considered to be tractable. The envisaged application is for snow and ice mapping and ocean wind vector measurement. The vastly increased complexity of the high-frequency waveband may not be justified by the scientific benefit and operation at an additional lower frequency such as 18 GHz may give improved classification, though with reduced spatial resolution. The authors describe the outline design for a polarimetric, mm-wave SAIR. One-dimensional aperture synthesis employs a hybrid technique in which a long linear array of real-aperture stick antennas form over-lapping fan beams on the ground and aperture synthesis within the fan beams enables synthesis of the mm-wave image. Critical aspects for building a high-resolution, mm-wave ESTAR are system calibration and the construction of stick antennas that will be 3 m long and about half a wavelength wide.
2016-12-16T09:03:50ZHarvey, A.R.Greenaway, A.H.Camps Carmona, Adriano JoséCorbella Sanahuja, IgnasiTorres Torres, FranciscoBara Temes, Francisco JavierMartín Neira, ManuelAn outline design for a dual-band mm-wave polarimetric SAIR has been presented and is considered to be tractable. The envisaged application is for snow and ice mapping and ocean wind vector measurement. The vastly increased complexity of the high-frequency waveband may not be justified by the scientific benefit and operation at an additional lower frequency such as 18 GHz may give improved classification, though with reduced spatial resolution. The authors describe the outline design for a polarimetric, mm-wave SAIR. One-dimensional aperture synthesis employs a hybrid technique in which a long linear array of real-aperture stick antennas form over-lapping fan beams on the ground and aperture synthesis within the fan beams enables synthesis of the mm-wave image. Critical aspects for building a high-resolution, mm-wave ESTAR are system calibration and the construction of stick antennas that will be 3 m long and about half a wavelength wide.Scattering and emissivity of rain events using boundary element method
http://hdl.handle.net/2117/89163
Scattering and emissivity of rain events using boundary element method
Duffo Ubeda, Núria; Vall-Llossera Ferran, Mercedes Magdalena; Camps Carmona, Adriano José; Corbella Sanahuja, Ignasi; Bará Temes, Francisco Javier; Torres Torres, Francisco
The theory of thermal microwave emission from a bounded medium containing random nonspherical discrete scatters is studied. It is known that for a medium of constant temperature the emissivities can be related to the bistatic scattering coefficients. Such relations hold for the four Stokes parameters. The down-welling polarimetric emission of the rain can be computed by means of the radiative transfer equation, which contains the four Stokes parameters. In order to apply the above equation to a realistic rain event, raindrop shapes have to be taken into account in the computation of the scattering amplitudes. Those shapes were obtained by Pruppacher and Pitter and are quite different from a sphere when the size increases. In this paper a procedure based in the Boundary Element Method (B.E.M.) is presented to compute the scattering amplitudes for each drop shape. Results are then averaged for all drop radii with a weighting function given by the Laws-Parson law. This law establishes the relationship between the drop size distribution and the rain intensity. A Gaussian distribution of the drop canting angle due to the wind has been also considered. Finally, some numerical results are presented. The scenario consists of a rain cell of 4 Km height at a uniform temperature, considering the wind effect. The values of the rain intensity and wind speed and direction have been obtained from realistic measurements recorded by a meteorological station located in campus. In order to validate these results, the four Stokes parameters obtained with these simulations were compared with the ones measured by a X-band polarimetric radiometer developed in our laboratory.
2016-07-25T12:40:49ZDuffo Ubeda, NúriaVall-Llossera Ferran, Mercedes MagdalenaCamps Carmona, Adriano JoséCorbella Sanahuja, IgnasiBará Temes, Francisco JavierTorres Torres, FranciscoThe theory of thermal microwave emission from a bounded medium containing random nonspherical discrete scatters is studied. It is known that for a medium of constant temperature the emissivities can be related to the bistatic scattering coefficients. Such relations hold for the four Stokes parameters. The down-welling polarimetric emission of the rain can be computed by means of the radiative transfer equation, which contains the four Stokes parameters. In order to apply the above equation to a realistic rain event, raindrop shapes have to be taken into account in the computation of the scattering amplitudes. Those shapes were obtained by Pruppacher and Pitter and are quite different from a sphere when the size increases. In this paper a procedure based in the Boundary Element Method (B.E.M.) is presented to compute the scattering amplitudes for each drop shape. Results are then averaged for all drop radii with a weighting function given by the Laws-Parson law. This law establishes the relationship between the drop size distribution and the rain intensity. A Gaussian distribution of the drop canting angle due to the wind has been also considered. Finally, some numerical results are presented. The scenario consists of a rain cell of 4 Km height at a uniform temperature, considering the wind effect. The values of the rain intensity and wind speed and direction have been obtained from realistic measurements recorded by a meteorological station located in campus. In order to validate these results, the four Stokes parameters obtained with these simulations were compared with the ones measured by a X-band polarimetric radiometer developed in our laboratory.Modelo de transistores MESFET en régimen no lineal
http://hdl.handle.net/2117/88876
Modelo de transistores MESFET en régimen no lineal
Corbella Sanahuja, Ignasi; Legido, Jm; Pradell i Cara, Lluís
2016-07-19T07:29:03ZCorbella Sanahuja, IgnasiLegido, JmPradell i Cara, LluísMethod of moments applied to the analysis of rough surfaces modelled by fractals
http://hdl.handle.net/2117/88555
Method of moments applied to the analysis of rough surfaces modelled by fractals
Vall-Llossera Ferran, Mercedes Magdalena; Duffo Ubeda, Núria; Camps Carmona, Adriano José; Corbella Sanahuja, Ignasi; Bará Temes, Francisco Javier; Torres Torres, Francisco
The Scattering and Emissivity of rough surfaces involve solutions to non-linear differential equations. Different approaches have been used in the literature to obtain approximate solutions under some hypothesis. For example Kirchhoff solution is used when the roughness is gentle on the scale of the wavelength.
In this paper the Method of Moments is used to analyze the scattering of arbitrary surfaces. No approximation about the scale roughness is necessary. Both Gaussian and Fractal surfaces have been modeled and compared. The introduction of fractal geometry provides a new tool to describe natural rough surfaces. A first inside to the properties and parameters that describe fractal geometry has been done in order to characterize them statistically. It has been demonstrated that geometrical and scattering characteristics are controlled by Fractal descriptors, including fractal dimension.
As a first step, our simulations refer to a (topological) one-dimensional (1-D) profile embedded in a two-dimensional (2-D) space. Physically, this corresponds to assume that both the electromagnetic field and the surface height are constant along a fixed direction. Extension to the case of a 2-D surface embedded in a three-dimensional (3-D) space is not conceptually difficult, but any simulation run requires a much longer computational time. Furthermore, scattering results obtained for 1-D profiles give also a good indication of scattering dependence on 2-D surface parameters.
2016-07-06T13:26:55ZVall-Llossera Ferran, Mercedes MagdalenaDuffo Ubeda, NúriaCamps Carmona, Adriano JoséCorbella Sanahuja, IgnasiBará Temes, Francisco JavierTorres Torres, FranciscoThe Scattering and Emissivity of rough surfaces involve solutions to non-linear differential equations. Different approaches have been used in the literature to obtain approximate solutions under some hypothesis. For example Kirchhoff solution is used when the roughness is gentle on the scale of the wavelength.
In this paper the Method of Moments is used to analyze the scattering of arbitrary surfaces. No approximation about the scale roughness is necessary. Both Gaussian and Fractal surfaces have been modeled and compared. The introduction of fractal geometry provides a new tool to describe natural rough surfaces. A first inside to the properties and parameters that describe fractal geometry has been done in order to characterize them statistically. It has been demonstrated that geometrical and scattering characteristics are controlled by Fractal descriptors, including fractal dimension.
As a first step, our simulations refer to a (topological) one-dimensional (1-D) profile embedded in a two-dimensional (2-D) space. Physically, this corresponds to assume that both the electromagnetic field and the surface height are constant along a fixed direction. Extension to the case of a 2-D surface embedded in a three-dimensional (3-D) space is not conceptually difficult, but any simulation run requires a much longer computational time. Furthermore, scattering results obtained for 1-D profiles give also a good indication of scattering dependence on 2-D surface parameters.Evaluation of MIRAS space borne instrument performance: snap shot radiometric accuracy and its improvement by means of pixel averaging
http://hdl.handle.net/2117/88554
Evaluation of MIRAS space borne instrument performance: snap shot radiometric accuracy and its improvement by means of pixel averaging
Camps Carmona, Adriano José; Torres Torres, Francisco; Bará Temes, Francisco Javier; Corbella Sanahuja, Ignasi; Martín Neira, Manuel
2016-07-06T13:19:37ZCamps Carmona, Adriano JoséTorres Torres, FranciscoBará Temes, Francisco JavierCorbella Sanahuja, IgnasiMartín Neira, Manuel